purification of strom water using sand filter

Purification of Strom Water Using Sand Filter

األمطار باستخدام المرشح الرمليتنقية مياه

Submitted By

Kamel Hajjaj

Supervised By

Dr. Abdelmajeed Nassar

A thesis submitted in partial fulfillment of the requirement for Degree of

Master of Science in Infrastructure Engineering

November 2011

Islamic University of Gaza

High Studies Deanery

Faculty of Engineering

Master in Science

Infrastructure Engineering

ii

الرحيم الرحمن هللا بسم

ينالله}ي رفع ينمنكمآمن واالذ خبي{نتعملوباواللهدرجاتالعلمأوتواوالذ

11ةياآلاجملادلة

يمالعظاهللصدق

iii

DEDICATION

I would like to dedicate this work to my family

specially my father and mother who supported me

in all stages of my life, to my brothers and sisters

and to my loving caring wife, for their sacrifice

and endless support, finally to my children Roaa

and Mohammed.

iv

ACKNOWLEDGMENT

I extend my sincere appreciation and special thanks to my supervisor Dr. Abdelmajeed

Nassar, for his guidance, patience and encouragement.

I would like to thank all lecturers at Islamic University in Gaza, who have helped me

during my study of Infrastructure Civil Engineering Master Program. They are Prof. Dr.

Shafik Jendia, Dr. Abdelmajid Nassar, Dr. Fahid Rabah, Dr. Essam H. Almasri, Dr.

Nabil I. El-Sawalhi, Dr. Husam Al-najar.

Finally, I would like to thank all the staff of the Material and soil Lab. at the Islamic

university of Gaza especially Eng. Ahmed Al Kurd, Eng. Adel Hamad and Mr. Amjad

Abu Shamalla and thank all the staff of the Laboratory of Environment and Earth

Sciences, especially Mr. Raed M. Al-khaldi, Mr. Azmy Abu Daggah and Mr. Alaa al

Juaab who have supported and encouraged me to accomplish this work.

v

Abstract

The rain water is an important source to feed to the groundwater aquifer, whether directly

or by harvesting and recharging. The importance of purification is to reduce the risk of

pollutants from runoff rainwater. The use of sand filter as a technique which is not

expensive and commonly for removing contaminants from the water and wastewater

treatment industries. In this research, the selected methodology used is laboratory testing,

by manufacturing plant to experimented the appropriate sand filter for purification and

made simulation for the infiltration of storm water through sand filter depth of 2 meters,

in order to find the relationship between the depth-of-hand, and the removal of suspended

solids and fecal coliforms bacteria on the other hand, to knowledge the effective depth

influential that gets the purification.

The research results during three days of infiltration show that the sand filter can provide

purified water with a concentration of suspended solids less than 20 mg / liter at a depth

of 75 cm and completely removes fecal coliform bacteria at a depth of 150 cm. Finally,

the research tested the increased concentration of suspended solids or fecal coliforms and

found that no significant impact of that on the purification and the percentage of removal,

but it is expected increase the occurrence of clogging in the filter.

vi

ملخص البحث

رى ي حما، حجع انا رى إعادة أ خى أ كاج طبعت ساء انجفت انخضااث نخغزت او يصذس االيطاس يا

حمت يا األيطاس حك ف حمهم انخاطش اناحجت ي انهراث انخ حخعشض نا أراء انسشا عه أت فئ

انصشف األيطاس يا نخمت انشائعت انكهفت غش انطشق ي كخمت عخبش انشيه انششح اسخخذاو إ األسض،

يحاكاة يخبش نهخعشف عه فعانت انششح انشيه رنك ي خالل عم حى عم فحص انبحذ زا ف. انصح

ي كم إصانت ب احت ي انعك ب انعاللت إجاد بغشض يخش، 2 عم سيه يششح ف األيطاس يا نخششح

عهت انخمت بكفاءة عانت. ف حخى انز انؤرش انعك يعشفت أخش احت ي انمنت انبكخشا انعانمت اناد

عط يا انشيه انششح أ أاو رالرت يخاصم نذة حششح عم خالل ي حى انحصل عها انخ حؤكذ انخائج

عذ انمنت انبكخشا كايم بشكم ضم سى 57 عك عذ انعانمت اناد ي نخش/يج 22 ي ألم حشكض ححخ عه

أرش ال أ انمنت انبكخشا أ انعانمت اناد حشكض صادة كا أظشث انخائج ي خالل فحص سى، 072 عك

إسذاد ف انششح انشيه. حذد حضذ ي احخانت أ ك نك اإلصانت سبت انخمت عه نزنك يحسط

vii

TABLE OF CONTENTS

CHAPTER 1 INTRODUCTION 1

1.1 BACKGROUND ........................................................................................................ 1

1.2 STATEMENT OF THE PROBLEM ................................................................................ 2

1.3 RESEARCH SCOPE AND OBJECTIVES ....................................................................... 3

1.3.1 Scope ................................................................................................................. 3

1.3.2 Objectives .......................................................................................................... 3

1.4 METHODOLOGY ...................................................................................................... 3

1.5 TENTATIVE TABLE OF CONTENTS FOR THE THESIS ................................................. 5

CHAPTER 2 LITERATURE REVIEW 6

2.1 POLLUTANTS IN STORM WATER .............................................................................. 6

2.2 FILTER MEDIA ........................................................................................................ 8

2.3 FACTORS INFLUENCING ON FILTRATION AND PERFORMANCE .................................. 8

2.4 TYPE OF SAND FILTER ............................................................................................. 9

2.4.1 Slow Sand Filter ................................................................................................ 9

2.4.2 Rapid Sand Filter ............................................................................................ 10

2.5 FILTRATION PROCESS THEORY ............................................................................. 10

2.5.1 Mechanism in Rapid Sand Filtration .............................................................. 11

2.5.2 Mechanism in Slow Sand Filtration ................................................................ 12

2.6 PRESENT REMOVAL BY FILTRATION ...................................................................... 12

2.7 SUSPENDED SOLIDS .............................................................................................. 13

2.8 FECAL COLIFORMS ............................................................................................... 13

2.9 DEPTH OF FILTER .................................................................................................. 14

CHAPTER 3 METHODOLOGY 15

3.1 EXPERIMENTAL DESCRIPTION ............................................................................... 15

3.2 MATERIALS .......................................................................................................... 16

3.3 EXPERIMENTAL APPARATUS ................................................................................. 16

3.4 EXPERIMENTAL SCENARIOS .................................................................................. 17

3.5 TESTING PARAMETERS ......................................................................................... 17

3.6 SAMPLES COLLECTION ......................................................................................... 17

3.7 SYSTEM OPERATION ............................................................................................. 18

viii

3.8 THE EXPECTED RESULTS ....................................................................................... 20

3.9 CALCULATIONS..................................................................................................... 20

3.10 SAMPLES TESTS METHODS .................................................................................... 20

3.10.1 Fecal coliforms ............................................................................................... 20

3.10.2 Suspended Solid .............................................................................................. 21

CHAPTER 4 RESULTS AND DISCUSSION 23

4.1 SIEVE ANALYSIS FOR FILTER'S MEDIA ................................................................... 23

4.2 RESULTS OF CONTINUOUS THREE DAYS OF INFILTRATION ..................................... 23

4.2.1 Fecal coliforms removal in the three days of infiltration ............................... 25

4.2.2 Suspended solid removal along the three days of infiltration ......................... 31

4.3 EFFECT OF DIFFERENT CONCENTRATIONS OF FECAL COLIFORMS ........................... 36

4.4 EFFECT OF DIFFERENT CONCENTRATIONS OF SUSPENDED SOLID ........................... 42

CHAPTER 5 CONCLUSIONS AND RECOMMENDATIONS 46

5.1 CONCLUSIONS ....................................................................................................... 46

5.2 RECOMMENDATIONS ............................................................................................. 47

REFERENCES 48

APPENDIX: PHOTOS SHOW THE METHOD OF THE WORK IN THE

LABORATORY 51

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LIST OF FIGURES

Figure ‎1.1: Flow chart of the research methodology ..................................................... 4

Figure ‎2.1: Schematic of basic filtration principles (Schmitt & Shinault, 1998) ............. 11

Figure ‎2.2: Concentrations of fecal for all urban land uses (Pitt & Maestre, 2005) ......... 14

Figure ‎3.1: Schematic diagram of the system ............................................................. 15

Figure ‎3.2: Collecting of water effluent .................................................................... 18

Figure ‎3.3: Petri dishes after being incubated for fecal coliforms colonies count ........... 21

Figure ‎4.1: Grain size distribution of filter materials .................................................. 23

Figure ‎4.2: the left bottle (influent of storm water) versus the right bottle (effluent of

treated storm water at depth 2m) .............................................................................. 25

Figure ‎4.3: Percent removal of fecal coliforms along three days of infiltration .............. 25

Figure ‎4.4: Percent removal of fecal coliforms vs specified depths in the first day ......... 26

Figure ‎4.5: Percent removal of fecal coliforms vs specified depths in the second day ..... 26

Figure ‎4.6: Percent removal of fecal coliforms vs specified depths in the third day ........ 26

Figure ‎4.7: Number of fecal coliforms effluent vs each depthin the first day ................. 27

Figure ‎4.8: Number of fecal coliforms in the effluent vs each depth in the secod day ..... 27

Figure ‎4.9: Number of fecal coliforms in the effluent vs each depth in the third day ...... 28

Figure ‎4.10: Relationship between the depth of filter and the FC average % removal ..... 29

Figure ‎4.11: Petri dishes for one of the fecal coliforms tests ........................................ 30

Figure ‎4.12: Surface layer of filter before infiltration (right) and after (left) .................. 30

Figure ‎4.13: Percent removal of suspended solid along three days of infiltration ........... 31

Figure ‎4.14: Percent of removal of suspended solid vs each depth in the first day .......... 31

Figure ‎4.15: Percent of removal of suspended solid vs each depth in the second day ..... 32

Figure ‎4.16: Percent removal of suspended solid vs each depth in the third day ............. 32

Figure ‎4.17: Concentration of suspended solid effluents vs each depth in first day ........ 33

file:///F:/Amr%20files%202/Kamel%20Hajaj/thesis/Final%20Modified/Final%20Files%2026.09.2011/2003%20Final%20Modified%20thesis%20final%2023.09.2011.docx%23_Toc306263091

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Figure ‎4.18: Concentration of suspended solid effluents vs each depth in second day .... 33

Figure ‎4.19: Concentration of suspended solid effluents vs each depth in third day........ 33

Figure ‎4.20: Relationship between the depth of filter and the SS average % removal ..... 35

Figure ‎4.21: Percent removal of fecal coliforms at influent 36000 col./100 ml .............. 37

Figure ‎4.22: Depth percent removal of fecal coliforms at influent 36000 col./100 ml ..... 38

Figure ‎4.23: Number of fecal coliforms (col./100ml) at influent 36000 col./100 ml ....... 39

Figure ‎4.24: Percent removal of fecal coliforms at influent 74000 col./100 ml .............. 40

Figure ‎4.25: Depth percent removal of fecal coliforms at influent 74000 col./100 ml ..... 41

Figure ‎4.26: Number of fecal coliforms (col./100 ml) at influent 74000 col./100 ml ...... 42

Figure ‎4.27: Depth percent removal of suspended solid at influent 1468 mg/l ............... 44

Figure ‎4.28: Depth percent removal of suspended solid at influent 1468 mg/l ............... 44

Figure ‎4.29: Concentration of suspended solid in the effluent at different depths ........... 45

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LIST OF TABLES

Table ‎2.1: Typical Pollutant Concentrations in Urban Storm water (Schueler, 1997) ....... 7

Table ‎2.2: Median Values for Pollutants of different land areas (Pitt et al. 2003) ............. 7

Table ‎3.1: Sieves size for sand filter media................................................................ 16

Table ‎4.1: The results of three continuous days of infiltration ...................................... 24

Table ‎4.2: Analysis of fecal coliforms in the efflent at each depth along three days ...... 28

Table ‎4.3: Depth grouping for results and analysis of fecal coliforms in the effluent ...... 29

Table ‎4.4: Analysis of effluent suspended solid along three days ................................. 34

Table ‎4.5: Depth grouping for results analysis of effluent suspended solid .................... 36

Table ‎4.6: Percent removal of fecal coliforms at influent 36000 col./100 ml ................. 37

Table ‎4.7: Percent removal of fecal coliforms at influent 74000 col./100 ml ................. 40

Table ‎4.8: Percent removal of suspended solid at influent 1468 mg/l ........................... 43

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LIST OF ABBREVIATIONS

APHA American Public Health Association

AWWA American Water Works Association

BMP Best Management Particle

BOD Biological Oxygen Demand

CFU Colony Forming Unit

CMWU Coastal Municipalities Water Utility

DEP Department Of Environmental Protection

COD Chemical Oxygen Demand

CSOs Combined Sewer Overflow

DOC Dissolved Organic Carbon

EPA Environmental Protection Agency

FC Fecal Coliform

KFUPM King Fahd University of Petroleum and Minerals

MECC Mountain Empire Community College

MPN Most Probable Number

NTU Nephelometric Turbidity Unit

PCBS Palestinian Central Beauru of Statistics

PCSWM Pierce County Storm Water Management

PVC-U Polyvinyl Chloride - Unplasticized

SS Suspended Solids

TSS Total Suspended Solids

WEF Water Environment Federation

Chapter 1 Introduction

1


1.1 Background

Gaza strip located at the eastern edge of the Mediterranean in a semi-arid region where

rainfall is falling in the winter season from October to April, the rate of rainfall is varying

in the Gaza Strip and ranges between 200mm/year in the south to about 400mm/year in

the north, while the long term average rainfall rate in all over the Gaza Strip is about

317mm/year(CMWU, 2010), the strip consider as the densest populated areas of the

world 1.5 million and growth rate 3.5%(PCBS, 2008), in an area of 365 km2, it is one of

the scarce water countries. The groundwater aquifer which is part of the coastal aquifer

that naturally recharged from rainfall consider as the only resource of the water that

supply ofall kind of human usage in the Gaza Strip (domestic, agricultural and industrial).

The Gaza Strip has been suffering from an increasing shortage of water, the demand water

much exceeds water supply, the renewable amount of water from rainfall that replenishes

the aquifer is much less than the water demand(Hamdan, et al. 2007), the reasons for that

shortage are growing demands by continuous increasing of population lead to

overdrafting from aquifer, resulted in dramatic urban expansion, which has a direct

influence in reducing groundwater recharge and increasing the surface run-off.

Sand filtration is a commonly-used technique for removing contaminants from the water

and wastewater treatment industries, during the last decade, the use of sand filters has also

become an accepted treatment technique for stormwater, particularly in situations where

high property values reduce the cost-effectiveness (Ellis, 1984).

In the Gaza Strip there are several sites of infiltration applied, including Sheikh Radwan

basin which was constructed to collect stormwater from Gaza city and diverts it to this

basin, where water was supposed to be injected through special wells close to the basin.In

1997 and 1998, two projects were launched, the first one is treatment plant in Gaza city,

where part of the effluent is diverted to infiltration basins which have infiltration capacity

less than the effluent flow. The rest of effluent is pumped to the sea. The second project is

the storm water collection in North Gaza, where storm water is collected in retention

basin in Jabalia City and then pumped to infiltration basins located close to the existing

wastewater treatment plant at BeitLahia. This project has been started few years ago in

Khan Yunis area, where stormwater will be collected from all areas in the City and will be


2

diverted or pumped to a large infiltration basin in the west of the City. Furthermore, other

two small infiltration basins inside Khanyonis camp will be used in this project.

Infiltration of treated wastewater is planned to be implemented in spread basins besides

the proposed wastewater treatment plants of both Khanyonis and Rafah (Hamdan & Jaber,

2001).

1.2 Statement of the Problem

The population and urbanization incensement led to increasing the quantity of runoff

while decreasing in the natural infiltration, this fact led to search about the useful solution

of this problem, to contribution the improvement of the quality and the quantity of

groundwater, and to be more focus to find the tools for treatment of storm water and

recharge it to the groundwater. In Gaza Strip which is suffering from difficult economic

situations, the main goal is to find low-cost system for storm water purification and sand

filter could be a solution.

The benefits of stormwater infiltration including the usual benefits of stormwater

management, the prevention of flooding and erosion, coupled with the benefit of

groundwater recharge, which is especially critical in the more arid regions. Infiltration of

stormwater offers the advantage of increased groundwater recharge, thereby raising

aquifer levels. It also offers the potential to limit non-point source pollution by

introducing a filter medium; Soil has been shown to be a very effective filter medium

which normally protects the groundwater from contamination by pollutants (Losco &

Valentine, 2003).

Generally, the stormwater in Gaza contains high concentration of suspended solids due to

the high number of the un-paved roads in the city (Hamdan & Jaber, 2001). After rainfall

intense on flat or pitched roofs to the streets, this water flows quickly mixing with silage

flow or untreated sewage. Such flows soon become a nuisance with potential health

hazards or major flooding problems (Al-Najar & Adeloye, 2005).

Clark and Pitt (1999) shows that after reviews of the research being done on direct

infiltration of urban runoff, contamination of groundwater has occurred by infiltration of

urban runoff containing the following problem substances: Nutrients, Organics and

Pesticides, Pathogenic Microorganisms, Metals, and Solids (Suspended and Dissolved).


3

1.3 Research Scope and Objectives

1.3.1 Scope

The main goal of this research is to investigate the feasibility of using sand filter for

purification of storm water.

1.3.2 Objectives

The primary aim of this research is to reach the optimum efficiency of using sand filter for

purification of stormwater, by examining the depth of the media and then investigating the

treatment efficiency by choosing two parameters; physical parameter (i.e. suspended

solid, and biological parameter (i.e. fecal coliforms).

More specifically, the research work is intended to achieve the following objectives:

Identify the relationship between the depth of sand filter and percent of suspended

solid removal.

Identify the relationship between the depth of sand filter and percent of fecal

coliforms removal.

1.4 Methodology

To achieve the objectives of this research, the following tasks have been executed:

1. Conducting a literature review to the related subjects of the research.

2. Collecting data about the stormwater in Gaza Strip.

3. Take sample of the sand that used in BietLahia infiltration Basin, to use it in

laboratory study, also experiment its characteristic in terms of sieve analysis, and

permeability, and samples of stormwater runoff that flow to the basin.

4. Preparing and manufacturing the laboratory plant.

5. Checking the test system, by applying it for continuous three days, then collect the

results and conclude the relationships.

6. Discussing the results, conclusion and recommendations of the research that aimed

to using sand filter for purification of stormwater.

Figure (1.1) shows a flow chart which explains the methodology of this research.


4

Literature reviews

Data Collection and

Sample selecting

Experimental Program

Sample testing Preparing a laboratory

plant

Checking the test system

Discussing the testing

results

Conclusions and

Recommendations

Figure 1.1: Flow chart of the research methodology


5

1.5 Tentative Table of Contents for the Thesis

The research is organized into different chapters that range from chapter 1 to 5 as follows:

Chapter 1(Introduction): this chapter consists of a general introduction with an overview

of the stormwater infiltration, problem identification, objectives and methodology of the

research.

Chapter 2 (Literature Review): this chapter begins with a brief literature review of

pollutants in storm water, filter media, filtration performance and mechanism, type of

sand filter, percent removal and effect of depth of sand filter.

Chapter 3 (Methodology): this chapter describes the experimental program in laboratory,

and test method.

Chapter 4 (Results and Discussions): this chapter includes a summary of the

experimental results, and discussion of the laboratory analysis.

Chapter 5 (Conclusions and Recommendations): this chapter gives conclusions and

recommendations about the research.

Chapter 2 Literature Review

6


Filtration with sand media has been used for over a century to treat water and wastewater.

The use of sand filtration for treatment of storm water has developed recently, generally

to treat runoff from streets, parking lots, and residential areas (PCSWM, 2009).

Storm water runoff picks up debris, sediment, and other contaminants as it seeks low

areas, where it can pool and cause flooding problems. Common contaminants of storm

water runoff include sediment, nutrients, toxic substances, oxygen-demanding materials,

and bacteria all of which can seriously degrade the quality of receiving waters (Balousek,

2002).

Filtration defined as an interaction between a suspension and a filtering material,

pollutants are removed from the solution when they become attached to the media or to

previously captured particles, using of sand filtration is common for drinking water and

wastewater treatment, Sand filters also popular as storm water runoff treatment (Clark and

Pitt,1999).

Storm water infiltration into the soil is a viable and practical method of storm water

management on many sites. The soil can provide an excellent filter medium to remove

contaminants and protect groundwater from pollution while slowing the introduction of

water into the water table and surface waters and providing groundwater recharge. (Losco

& Valentine, 2003).

2.1 Pollutants in Stormwater

Storm water constituents: Sediment, Nutrients: nitrogen and phosphorous, Oil ,grease, and

organic chemicals, Bacteria and viruses, Salt, and Metals (Buechter, 2008). Schueler

(1997) summarized typical pollutant concentrations found in urban storm water as

illustrated in Table (2.1); Pitt et al. (2003) summarized the median values for selected

parameters pollutants of different land areas illustrated in Table (2.2).


7

Table ‎2.1: Typical Pollutant Concentrations in Urban Storm water (Schueler, 1997)

Typical Pollutants Found in Strom water

Runoff (Data source) Units Average Concentration (1)

Total Suspended Solids (a) mg/l 80

Total Phosphorous (b) mg/l 0.30

Total Nitrogen (a) mg/l 2.0

Total organic Carbon (d) mg/l 12.7

Fecal Coliform Bacteria (c) MPN/100 ml 3600

E. coli Bacteria (c) MPN/100 ml 1450

Petroleum Hydrocarbons (d) mg/l 3.5

Cadmium (e) µg/l 2

Copper (a) µg/l 10

Lead (a) µg/l 18

Zinc (e) µg/l 140

Chlorides (f) (winter only) mg/l 230

Insecticides (g) µg/l 0.1 to 2.0

Herbicides (g) µg/l 1 to 5.0

(1) These concentrations represent mean or median storm concentrations measured at typical sites, and may

be greater during individual storms. Also note that mean or median runoff concentrations from storm

water hotspots are 2 to 10 times higher than those shown here. Units = mg/l = milligrams/liter, µg/l =

micrograms/liter.

Table ‎2.2: Median Values for Pollutants of different land areas (Pitt et al. 2003)

Parameter Overall Residential commercial Industrial Freeways Open Spaces

Area (acres) 56 57.3 38.8 39 1.6 73.5

% Imprev. 54.3 37 83 75 80 2

Precip. Depth (in) 0.47 0.46 0.39 0.49 0.54 0.48

TSS (mg/L) 58 48 43 77 99 51

BOD5 (mg/L) 8.6 9 11.9 9 8 4.2

COD (mg/L) 53 55 63 60 100 21

Fecal Coliform (mpn/100mL) 5081 7750 4500 2500 1700 3100

NH3 (mg/L) 0.44 0.31 0.5 0.5 1.07 0.3

NO2+NO3 (mg/L) 0.6 0.6 0.6 0.7 0.3 0.6

Nitrogen, Total Kheldahl (mg/L) 1.4 1.4 1.6 1.4 2 0.6

Phos., filtered(mg/L) 0.12 0.17 0.11 0.11 0.2 0.08

Phos., total (mg/L) 0.27 0.3 0.22 0.25 0.25 0.25

Cd, total (µg/L) 1 0.5 0.9 2 1 0.5

Cd, filtered (µg/L) 0.5 ND 0.3 0.6 0.68 ND

Cu, total (µg/L) 16 12 17 22 35 5.3

Cu, Filtered (µg/L) 8 7 7.6 8 10.9 ND

Pb, total (µg/L) 16 12 18 25 25 5

Pb, filtered (µg/L) 3 3 5 5 1.8 ND

Ni, total (µg/L) 8 5.4 7 16 9 ND


8

Parameter Overall Residential commercial Industrial Freeways Open Spaces

Ni, filtered (µg/L) 4 2 3 5 4 ND

Zn, total (µg/L) 116 73 150 210 200 39

Zn, filtered (µg/L) 52 33 59 112 51 ND

ND = not detected, or insufficient data to present as a median value.

2.2 Filter Media

AWWA (2001), Torrens et al.(2009), Anderson et al.(1985), and Woelkerset al.(2006)

states that the successful choice of a filter media as sand filter to produced

satisfactory desired pollutant removal performance depended upon the proper choice of :

the depth of the filters, type of sand, sand size and distribution, conditions of influent

water, quality of effluent, the filtration rate, and dosing regime and resting period

duration, all affected the hydraulic performance and purification efficiency of the filters.

(Torrens et al., 2009) stated that the sand used as the filter medium must be fine enough to

ensure the biological analyses, and coarse enough to avoid surface clogging and maintain

correct aeration. Granular media that is too coarse limited the retention time to a

point where adequate biological decomposition is not attained. Too fine media

limits the quantity of water that may be successfully filtered due to early filter

clogging(Anderson et al. 1985). Coarser sands have larger pore spaces that have high

flow-through rates but pass larger suspended particles. A very fine sand, or other fine

media filter has small pore spaces with slow flow-through rates and filter out smaller total

suspended solids (TSS) particles (Urbonas, 2003).

2.3 Factors influencing on filtration and performance

Overall filtration performance depends on many factors such as the desired treatment rate,

the quality of the water resource and the physical characteristics of the media (type, size

distribution, depth, and hydraulic loading rate) (Clark, 2007). In general, filter

performance has been evaluated by one or more of the following parameters, which was

used in Clark 2007 study:

Effluent of water quality (turbidity and suspended solids concentration; possibly

particle size distributions, and dissolved organic carbon concentration DOC).

Effluent heavy metal and/or organic concentrations (if applicable).

Water production (unit filter run volume) and,

Head-loss development (rate and time to backwash or media replacement if no

backwash is used).


9

Culp et al. (1978) concluded that the main factors influencing the filtering and trapping

processes are:

Suspended particle size: Filtration efficiency improves with larger particulate size.

Pore size: The space between the grains determines the size of particulate that can

be trapped.

Grain shape: Angular grains participate more in the mechanical straining process.

Filtration velocity: Filtration efficiency decreases with increasing velocity.

Temperature of liquid: The higher the water temperature is the more efficient

filtration is, although it normally cannot be controlled.

Chemical properties of the water and particle: A chemical filter aid may be added

to promote adhesion.

Flow rate is considered also from factors influencing the filtering performance; Khan

(1995) concluded from his study that the removal efficiency of coliphage decreased from

79 % to 75 % when the flow rate increased from 10 to 20 l/min keeping the sand depth and

sand size constant. Similar trends of reduced efficiencies at increased flow rates were

found for total coliforms, fecal coliforms and standard plate counts at 150 cm sand depth

and 0.5 mm of sand size.

2.4 Type of sand filter

Two types of filtration systems may be applied to construct storm water treatment: rapid

and slow.

2.4.1 Slow Sand Filter

HUISMAN & WOOD (1974)illustrated that in slow filtration, the media used is

considered as a fine sand, and the designed rate of downward flow of the water under

treatment normally lies between 0.1 and 0.4 m3/h per square meter of surface, The sand

media used has size of 0.2 to 0.4 mm (KFUPM, 2008).

It is the oldest type of large-scale filter, the sand removes particles from the water through

adsorption and straining, also removed a great deal of turbidity from water using

biological action. A layer of dirt, debris, and microorganisms builds up on the top of the

sand. This layer is known as schmutzdecke, which is German for "dirty skin. "The

schmutzdecke breaks down organic particles in the water biologically, and is also very

effective in straining out even very small inorganic particles from water (MECC, 2002).


10

The filter of this type may run for weeks or even months without cleaning. The suspended

solids and colloidal matter are deposited at the very top of the bed, from which they can

be removed by scraping off the surface layer to a depth of one or two centimeters. This

infrequent operation may be carried out by unskilled laborers using hand tools or by

mechanical equipment (HUISMAN & WOOD, 1974).

Slow sand filter according to its specifications have very low hydraulic rates, because they

do not have backwash systems. Slow sand filter generally has been used to treat storm

water, and considered mechanically simple in comparison to rapid sand filtration but

requires a much larger filter area (PCSWM, 2009).

2.4.2 Rapid Sand Filter

HUISMAN & WOOD (1974)illustrated that in rapid filtration, the media used

considerably coarser with an effective grain size of 0.6-2.0 mm. The interstices between

the grains are larger, providing less resistance to the downward flow, and thus permitting

higher velocities, usually in the range 5-15 m3 /m

2 /h.

Rapid sand filter can achieve relatively high hydraulic flow rates and clean automatically

using backwash the systems to remove accumulated solids(PCSWM, 2009).The

mechanism of particle does not use biological filtration and depend primarily on

adsorption and some straining (MECC, 2002).

The necessity for cleaning is to restore the capacity of the filter and the quality of the

effluent, which occurs at frequent intervals (often only one or two days).To clean

throughout its whole depth, by practical method in which high-pressure water is forced

upwards through the whole bed and compressed air or mechanical agitation is used to

scour the individual grains so that the accumulated impurities can be flushed away

(HUISMAN & WOOD, 1974).

2.5 Filtration Process Theory

The mechanism of filtration and removal depended on the type of sand filter which is

either slow or rapid.

Anderson et al. (1985) summarized the mechanism process that occurs to some degree

within the filter as physical, chemical, and biological treatment processes.

Straining, sedimentation, inertial impaction, interception, adhesion, flocculation,

diffusion, adsorption and biological activity have been suggested as mechanisms

of contaminant removal in filtration.


11

Straining: involves a mechanical sieve action as well as lodging of

particles in crevices.

Sedimentation: occurs as gravity settling takes place in the interstices of

the media.

Inertial impaction, interception, and adhesion: occur as particles moving

through the filter strike media granules and are removed.

Flocculation: Particles moving through the pores will also collide with each

other and flocculate causing subsequent removal by other mechanisms.

Diffusion: is important in the removal of very small particles such. as

viruses, and occurs because of the small interstices in porous media and

the fact that laminar flow exists.

Physical adsorption: of pollutants takes place on media surfaces due to

electrostatic, electrokinetic and van der Waals forces while chemical

adsorption occurs due to bonding and chemical interaction between

polluted water constituents and the filter media.

Biological activity: on the filter media results in removal of polluting

materials by biological assimilation and biosynthesis.

2.5.1 Mechanism in Rapid Sand Filtration

The filter process operates based on two principles, mechanical straining and physical

adsorption. Sand filtration is a "physical-chemical process for separating suspended and

colloidal impurities from water by passage through a bed of granular material. Water fills

the pores of the filter medium, and the impurities are adsorbed on the surface of the grains

or trapped in the openings." (Culp et al. 1978). The key to this process is the relative

grain size of the filter medium.

Figure (2.1) shows a schematic of basic filtration principles.

Figure ‎2.1: Schematic of basic filtration principles (Schmitt & Shinault, 1998)


12

2.5.2 Mechanism in Slow Sand Filtration

The purification achieved in a slow sand filter may be considered to be principally the

result of straining through the developed filter skin and the top few millimeters of sand,

together with biological activity. However, Huisman (1978) suggested mechanical

straining, sedimentation, adsorption, and chemical and biological activity as the important

process of slow sand filtration:

Sedimentation and straining take place usually during the first few days of operational.

The supernatant water above the sand bed is about 100 - 150 cm deep, depending upon

the design of filters. The average time that the sample remains above the sand bed ranges

from 3 to 12 hours, depending upon the filtration rate. The heavier particles of suspended

matter start to settle while the lighter particles are drawn into the pores between the sand

grains and removed by straining on the top few millimeters. During the filtration process,

a layer of inert deposits and biological matter forms on the top layer of the sand bed. This

layer is referred to as Schmutzdecke. Moreover, biological growth also occurs within the

sand bed and within the gravel support. Both the schmutzdecke and the biological growth

have significant effect in the purification mechanism (Farooqet al. 1993).

2.6 Present removal by filtration

The primary removal mechanisms of suspended solids are physical filtration and

sedimentation. Infiltration systems provide filtration of runoff but the percent removal of

solids depends on, among other variables, particle size and the size of the pore opening

between soil particles (Weiss et al. 2008).

Hsieh & Davis (2005) conducted both laboratory column tests and field studies. Column

percent removal of suspended solids ranged from 29% to greater than 96% and removal at

six field sites ranged from 77% to 99%.

Khan (1995) conducted field studies shows the average removal efficiencies among

fourteen different operational conditions ranged from 68% to 86%for coliphage, 78% to

99% for total coliforms, 79% to 99% for fecal coli forms, 82% to 96% for standard plate

counts, 22% to 64% for suspended solids and 33% to 62%for turbidity. The samples at

various sand depths of each filter were taken to study the removal of coliphage and

bacteria. It was found that most of the removal of coliphage and bacteria occurred in the

top layers of sand bed (75 cm) of the filter where low flow rates and coarse sand was

used. In case of high flow rates the maximum removal was achieved at 100 cm for both


13

coarse and fine sand filters. The influent concentrations of suspended solids and turbidity

ranged from 8 to 22 mg/l and 0.20 to 0.95 NTU respectively.

2.7 Suspended Solids

Total Suspended Solids (TSS) are solids in water that can be trapped by a filter. TSS can

include a wide variety of materials, such as silt, decaying plant and animal matter,

industrial wastes, and sewage. High concentrations of suspended solids can cause many

problems for stream health and aquatic life (Buechter, 2008).

Suspended solids, which are almost found in storm water runoff samples, can degrade

water quality(EPA, 1999).Construction and land-disturbing activities are the leading

source of suspended solids in storm water(EPA, 1999).Because metals, pesticides, and

petroleum hydrocarbons often are sorbed to solid surfaces, solids provide a means of

transport and accumulation of pollutants (EPA, 1999).

Woelkerset al. (2006) states that the likely minimum effluent concentrations are as

follows: 10 mg/L for suspended solids, 50 HACH color units, and 10 NTU for turbidity.

TSS concentration less than 20 mg/l consider water to be clear. Water with TSS levels

between 40 and 80 mg/l tends to appear cloudy, while water with concentrations over 150

mg/l usually appears dirty. The nature of the particles that comprise the suspended solids

may cause these numbers to vary (Pitt et al. 2003). EPA Committee on Water Quality

Criteria < 25 mg/L: no harmful effects or high level protection (Buechter, 2008).

DEP (1996) shows that total suspended solids was selected as the target pollutant

constituent for a removal standard because of its widespread contribution to water quality

and aquatic habitat degradation, because many other pollutant constituents including

heavy metals, bacteria, and organic chemicals sorb to sediment particles, and because

available data sets for BMP removal efficiency reveal that TSS has been the most

frequently and consistently sampled constituent, i.e.Bruijn and Clark (2003) concluded

that there are correlations between TSS and particulate runoff concentrations of

chromium, copper, and zinc, indicating that solids removal may reduce total metals

concentrations, therefore specific storm water treatment goals usually specify about 80%

reductions in suspended solids concentrations.

2.8 FecalColiforms

As part of the National Urban Runoff Program, fecal coliform was evaluated at 17 sites

for 156 storm events and, based on the results, concluded that coliform bacteria are


14

present at high levels in urban runoff and may exceed EPA water quality criteria during

and after storm events, (EPA, 1999).

Pitt &Maestre (2005) illustrated that the urban storm water has surprisingly high

concentrations of fecal coliform bacteria. Figure (2.2) summarizes data from several

studies, shows concentrations of fecal coliforms are well above the water quality standard

for all urban land uses. The primary sources of fecal coliform bacteria include pet waste,

wildlife, septic systems, illicit discharges, and combined sewer overflows (CSOs).

Figure ‎2.2: Concentrations of fecal for all urban land uses (Pitt &Maestre, 2005)

2.9 Depth of filter

From the past experience, it is learned that biological activity decreases with reducing the

filter’s depth. In other words, the biological activity is enhanced with increasing depths.

Therefore, the viruses and other suspended and organic matter have to travel more through

the sand bed and the possibility of removal of these impurities is significantly increasing.

Therefore, higher removal efficiency is expected at higher sand depths (Ellis, 1984).

Khan (1995) conducted field studies at most various comparisons made of sand size and

flow rate concluded that with respect to effect of sand depth, the removal of coliphage,

total coliforms, fecal coliforms and plate counts decreased when the sand depth was

decreased from 150 cm to 80 cm to 50 cm respectively. In most of the cases the trends

were higher removal efficiencies were obtained at lower flow rates, higher sand depths

and smaller sand size, respectively. In most of the cases indicated no significant effect of

flow rate and sand depth on removal of suspended solids.. .

Chapter 3 Methodology

15


The aim of this study is to investigate and to reach the optimum efficiency of using sand

filter for purification of storm water, by testing in laboratory the quality of effluent of

filtrated storm water samples at different depths of the sand filter media and by

investigating the efficiency of purification. The study considers two parameters; physical

parameter (i.e. suspended solids) and biological parameter (i.e. fecal coliforms) to reflect

the range of storm water purification along 2 meter of the sand filter.

3.1 Experimental description

A laboratory plant was locally manufactured and used in this study. Figure 3.1 shows a

schematic diagram of the system.

Figure ‎3.1: Schematic diagram of the system

The system consists of the following; 2.3 meters cylindrical PVC-U pipe with 8 inch

diameter, storm water tank, motion fan to avoid the settling of sediments, overflow tank to

collect the exceeded water, glass window with 5cm width and 50 cm height to monitor the

media, and 3/4 PE pipes to connect the different units together so water flows through the

system as designed.

12.5 cm

25 cm

37.5 cm

50 cm

75 cm

100 cm

150 cm

200 cm


16

The 8-inch cylindrical PVC-U pipe is filled with 200 cm height of sand media. The pipe

contains a number of valves at varying distances from the upper surface of the media; at

12.5 cm, 25 cm, 37.5 cm, 50 cm, 75 cm, 100 cm, 150 cm, and 200 cm respectively.

The sand filter media used in this system was collected from BietLahia infiltration basin

and was tested in the lab so as to determine its characteristics in terms of sieve analysis.

In the first stage, the experiment was continuously conducted having certain properties for

a period of three days. In the second stage, the system was operated with changing two

parameters; with increasing the concentration of suspended solids and once another with

increasing the concentration of coliforms bacteria.

Concentration of suspended solids and fecal coliforms are the main parameters used

during the operation to illustrate the relationship between them and the removal

efficiency.

3.2 Materials

Sand filter material used in the testing program was tested in term of sieve analysis. Filter

material was sieved through stainless steel sieves with the mesh sizes shown in Table 3.1.

Table ‎3.1: Sieves size for sand filter media

3.3 Experimental apparatus

The experimental apparatus composed of the following:

Collection runoff storm water tank, including the following components:

Water tank (500 liter);

Submersible motion fan; and

Electrical source

Components of sand filter, including the following components:

2.3 meter cylindrical PVC-U pipe with 8'' diameter filled sand filter media to

SIEVE SIZE

(mm) SIEVE #

1.18 #16

0.6 #30

0.425 #40

0.3 #50

0.15 #100

0.075 #200


17

depth of 2 m.

. The pipe contains a number of valves at varying distances from the upper

surface of the media; at 12.5 cm, 25 cm, 37.5 cm, 50 cm, 75 cm, 100 cm, 150 cm,

and 200 cm respectively.

Brass pipe connectors to connect between pipes and each valve.

Wire mesh was used between filter material and each valve in pipe.

Glass window 5cm x 50cm

Inlet and outlet pipes in the upper part of pipe

Polly ethylene pipe with a diameter of 3/4 inch to connect between the

components of the plant.

Water tank (200 liter) to collect overflow of water.

Valves for inlet and outlet of water to control the flow.

3.4 Experimental Scenarios

The experimental study used the following scenarios to study the purification of storm

water by sand filter:

1. Continuous three days of infiltration.

2. Increasing the number of fecal coliforms.

3. High concentration of suspended solid.

3.5 Testing Parameters

The following parameters were tested in the study:

1- Physical parameters (Suspended Solids).

2- Biological parameter (Fecal Coliforms).

3.6 Samples Collection

Samples were collected using sterilized 500 ml plastic bottles from both the influent and

the effluent outlets of the filters (see Figure 3.2). Samples collected for microbiological

analysis then were placed in an ice box with ice packs to maintain the temperature of 4°C.

Strict sterilized conditions were maintained throughout the collection and transportation

of these samples.

Each valve was opened at least one minute prior to sample collection so as to flush any

pollutant that may exist around each of depth valve Thus, accurate results can be obtained.


18

The sterilize bottles were numbered and labeled. Attention was also paid during sampling

to avoid mixing effluents as this could lead to a change in the percentage of fecal

coliforms.

For well and proper sampling, it was necessary to sterilize the sample bottles through

submerging them in boiling water for 5 minutes each. Representative samples were made

by taking three samples for each effluent depth valve and then mixing them to get a

composite sample.

The samples bottles were then immediately brought to the lab for analysis in term of fecal

coliforms and suspended solid concentrations. For suspended solids analysis, the samples

were separated in 100 ml bottles.

Figure ‎3.2: Collecting of water effluent

3.7 System Operation

After testing the sand filter media, the apparatus was assembled. Following this,

the system was operated first using clean water so that to wash the sand filter

media and to remove any impurities that may exist on it; this step continued till

reaching a steady state flow and till water runs clean.

The collector tank of 500 liters then was filled with storm water and all the valves

were closed excepting the drainage valve. The controlling of the influent storm

water flow was done through the tank valve as well.


19

In the first stage of the laboratory study, the infiltration test was continuously

conducted for three days to ensure continuity of the infiltration. To avoid clogging

of media, a low influent flow rate was adopted. The suspended solid removal and

fecal coliforms removal, at each different depth specified above were measured

and calculated.

In the second stage of the laboratory study, the effect of different concentrations of

fecal coliforms on filtration and treatment performance was investigated and

tested. The concentration of fecal coliforms in the influent storm water was

increased by adding specific and measured amount of wastewater. The added

wastewater was collected from one of the wastewater pumping stations and it had

at least two millions of coliforms per 100 ml. The system then was operated and

fecal coliforms removal were measured and calculated at the different depths.

In the third stage of laboratory study, the effect of different concentrations of fecal

coliforms on filtration and treatment performance was investigated similarly as in

stage 2 but by double increasing the concentration of fecal coliforms to the

influent storm water of the collection storm water tank. Specified and measured

quantities of wastewater were added as in step 2 then the system was operated. For

each depth, fecal coliforms removal were measured and calculated.

In the fourth stage of laboratory study, the effect of different concentrations of

suspended solids on filtration and treatment performance was investigated through

adding specified amounts of soil fillers and then operating the system. For each

depth suspended solid removals were measured and calculated to investigate the

effect of high concentration of suspended solids on filtration and treatment

performance.

It was important to wash the media after each experiment stage and to remove the

top layer of dirt on the surface of sand filter so as to reflect the actual performance

of the system and to ensure obtaining accurate results for infiltration and treatment

performance.

The results then have been presented and different relationships have been made

between them so that they can be easily discussed and analyzed, and from which

conclusions can be drawn.


20

3.8 The expected results

The expected results from this laboratory study are summarized below:

1. Continuous three days of infiltration.

1.1. Percent of suspended solid & fecal coliforms removal per day.

1.2. Concentration of suspended solid & fecal coliforms per day.

2. Effect of different concentrations of suspended solid.

3. Effect of increasing the number of fecal coliforms.

The relationships will be concluded and illustrated in charts and tables so that findings

can be better understood and discussed.

3.9 Calculations

Based on the experiment measurements, some items were calculated. The following

formulas are used for calculating the items;

Percent of suspended solid removal:

Percent of fecal coliforms removal:

3.10 Samples tests methods

3.10.1 Fecal coliforms

The membrane filter method (APHA, AWWA, WEF. 1998,Standard Methods for the

Examination of Water and Wastewater, 20 th Edition 9222 D) provides direct

enumeration of the fecal coliform group without enrichment or subsequent testing. The

results of the membrane filter test are obtained in 24 hours. An appropriate volume of

water sample or its dilution is passed through a membrane filter that retains the bacteria

present in the sample. The filter containing the microorganisms is placed on MFC agar in


21

a petri dish. The dish is incubated at 44.5 ± 0.2°C for 24 ± 2 hours. After incubation, the

typical blue colonies are counted under low magnification and the number of fecal

coliforms is reported per 100 ml of original sample (see Figure 3.3).

The concentration of fecal coliforms bacteria in water is measured to determine the

likelihood of contamination by microbiological organisms. Fecal coliforms are expressed

in colony forming units per 100 mL, CFU/100 mL, of water tested.

Figure ‎3.3: Petri dishes after being incubated for fecal coliforms colonies count

3.10.2 Suspended Solid

The method 2540 D (APHA, AWWA, WEF, 1992 Standard Methods for the Examination

of Water and Wastewater, 18 th Edition) is used for determining the total suspended solid.

A well-mixed sample is filtered through a weighed standard glass-fiber filter and the

residue retained on the filter is dried to a constant weight at 103°C to 105°C. The increase

in weight of the filter represents the total suspended solids.

If the suspended material clogs the filter and prolongs filtration, it may be necessary to

increase the diameter of the filter or decrease the sample volume. To obtain an estimate of

total suspended solids, calculate the difference between total dissolved solids and total

solids;

Calculation

(A-B) X 1000

mg total suspended solids/L =

sample volume, mL

where:

A = weight of filter + dried residue, mg, and

B = weight of filter, mg.


22

Method 208 E (APHA, AWWA, WEF, 1975, Standard Methods for the Examination of

Water and Wastewater, 14 th Edition); the residue from Method 2540 D is ignited to a

constant weight at 550+ 50 o C. The remaining solids represent the fixed suspended solids

while the weight loss on ignition represents the suspended volatile solids.

Chapter 4 Results and Discussion

23


The investigation of feasibility and performance of purification process by infiltration was

done by using filter made from PVC-U pipe filled with 200 cm height of sand media with

operating system.

Flow rate, concentration of suspended solids and fecal coliforms are the main parameters

used during the operation to illustrate the relationship between them and the removal

efficiency.

4.1 Sieve analysis for filter's media

Figure 4.1 illustrates the sieve analysis for the sand filter used in the system. It is clear

that the type is slow sand filter as the average size of particles ranges from 0.15 to 0.60

mm – the favorite range used for purification of storm water (PCSWM 2009).

Figure ‎4.1: Grain size distribution of filter materials

4.2 Results of continuous three days of infiltration

The sand filter was operated for a period of continues three days to monitor the infiltration

and treatment performance at the first stage of experiments and thus to study the removal

of suspended solid and fecal coliforms at each depth of the sand filter media; at 12.5 cm,

25 cm, 37.5 cm, 50 cm, 75 cm, 100 cm, 150 cm, and 200 cm respectively.

0

10

20

30

40

50

60

70

80

90

100

0.01 0.1 1 10

% P

assi

ng

Sieve opening (mm)

Particle size disribution curve (Tested Sand Filter)


24

The results of three days of infiltration for each media filter depth in term of suspended

solids and fecal coliforms are concluded in the Table 4.1.

Table ‎4.1: The results of three continuous days of infiltration

Cu

mu

lative De

pth

(cm)

1st Day 2

nd Day

3rd

Day

Suspended Solid Influent = 95 mg/l Suspended Solid Influent =

100mg/l Suspended Solid Influent = 108mg/l

Influent fecal coliforms =9000

col./100ml


col./100ml


col./100ml

SS

(mg/l)

SS

% rem

ov

al

F.C

. (col./ 1

00

ml)

FC

% rem

ov

al

SS

(mg/l)

SS

% rem

ov

al

F.C

. (col./ 1

00

ml)

FC

% rem

ov

al

SS

(mg/l)

SS

% rem

ov

al

F.C

. (col./ 1

00

ml)

FC

% rem

ov

al

12.5 32 66.3% 8000 11.1% 45 55.0% 5000 16.7% 50 53.7% 6000 -20.0%

25 24 74.7% 7000 22.2% 32 68.0% 5000 16.7% 42 61.1% 6000 -20.0%

37.5 18 81.1% 6000 33.3% 16 84.0% 4000 33.3% 17 84.3% 5000 0.0%

50 14 85.3% 5000 44.4% 13 87.0% 3000 50.0% 15 86.1% 2000 60.0%

75 13 86.3% 2000 77.8% 13 87.0% 1000 83.3% 12 88.9% 1000 80.0%

100 12 87.4% 2000 77.8% 13 87.0% 1000 83.3% 12 88.9% 1000 80.0%

150 10 89.5% 0 100.0% 11 89.0% 0 100.0% 10 90.7% 0 100.0%

200 8 91.6% 0 100.0% 9 91.0% 0 100.0% 8 92.6% 0 100.0%

Where: SS) suspended solid, & FC) fecal coliforms.


25

Figure ‎4.2: the left bottle (influent of storm water) versus the right bottle (effluent of

treated storm water at depth 2m)

4.2.1 Fecal coliforms removal in the three days of infiltration

Figure 4.3 (curves chart) summarizes the percent of fecal coliforms removal through 2 m

sand filter per day versus the specified depths of the sand filter media and their relation.

Figures 4.4, 4.5 and 4.6 summarize their relation for each single day of the three days

respectively using bar charts.

Figure ‎4.3: Percent removal of fecal coliforms along three days of infiltration

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

110%

0 25 50 75 100 125 150 175 200

% P

erce

nt

Rem

ova

l of

feca

l co

lifo

rm

Sand Filter Depth (cm)

1st Day

2nd Day

3rd Day


26

Figure ‎4.4: Percent removal of fecal coliforms vs specified depths in the first day

Figure ‎4.5: Percent removal of fecal coliforms vs specified depths in the second day

Figure ‎4.6: Percent removal of fecal coliforms vs specified depths in the third day

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

12.5 cm 25 cm 37.5 cm 50 cm 75 cm 100 cm 150 cm 200 cm

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%


0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%



27

The change of removal from depth to depth varies from day to day, but in general they

have a close pattern and there is no significant difference in the percentage of removal

between these three days with exception to the upper depths on the first day.

The number of fecal coliforms in the effluent at each sand filter depth at each day of the

three days of infiltration is summarized in Figures 4.7, 4.8 and 4.9.

Figure ‎4.7: Number of fecal coliforms effluent vs each depth in the first day

Figure ‎4.8: Number of fecal coliforms in the effluent vs each depth in the second day

0.00

1,000.00

2,000.00

3,000.00

4,000.00

5,000.00

6,000.00

7,000.00

8,000.00

9,000.00


0.00

1,000.00

2,000.00

3,000.00

4,000.00

5,000.00

6,000.00



28

Figure ‎4.9: Number of fecal coliforms in the effluent vs each depth in the third day

It is clearly shown form the figures that F.C is completely removed by infiltration through

sand filter after a depth of 150 cm in these three days, and also at depth 75 cm there is at

least 77.8% removal and the removal percent decreases day by day even at the third day.

It is found that there are some contaminations in the upper layer of the sand media due to

infiltration process which consequently affects the treatment performance.

The removals of fecal coliforms along the three days of infiltration is shown in Table 4.2

and Figure 4.10 which illustrate mainly the average percent removal and differential

percent increment of removal - which reflect the percent improvement of removal at each

depth.

Table ‎4.2: Analysis of fecal coliforms in the effluent at each depth along three days

Where:

1) Min. %removal: Minimum percent removal during the three days

2) Max. %removal: Maximum percent removal during the three days

3) Average %removal: Average percent removal during the three days

4) Differential increment %removal: percent improvement of removal each depth.

0.00

1,000.00

2,000.00

3,000.00

4,000.00

5,000.00

6,000.00

7,000.00


Depth Min.

%removal 1

Max.

%removal 2

Average

%removal 3

Differential increment

%removal 4

12.5 cm 0 16.7 9.27 -

25 cm 0 22.2 12.97 +3.7

37.5 cm 0 33.3 22.2 +9.23

50 cm 44.4 60 51.47 +29.27

75 cm 77.8 88.9 80.37 +28.9

100 cm 77.8 88.9 80.37 0

150 cm 100 100 100 +19.63

200 cm 100 100 100 0


29

Figure ‎4.10: Relationship between the depth of filter and the FC average % removal

Figure 4.10 shows the mathematical relation between the depth of Filter and the efficiency

of Fecal Coliform removal. The most representative equation was a polynomial (2nd

degree) as the factor (R2 = 0.96 which is close to 1).

The results and analysis shown in Table 4.2 can be presented in groups basis (i.e 12.50 -

25 cm) as shown below in Table 4.3, showing the change of performance and removal at

each depths range. Thus, results can be better understood, discussed and concluded.

Table ‎4.3: Depth grouping for results and analysis of fecal coliforms in the effluent

Depth range Effective

depth 1

Average

%removal 2


%removal 3

(12.5-25) cm 25 cm 12.97 -

37.5 cm 37.5 cm 22.2 9.23

50 cm 50 cm 51.47 28.27

(75-100) cm 75 cm 80.37 28.9

(150-200) cm 150 cm 100 19.63

Where:

1) Effective depth: Depth at which it gets removal.

2) Average %removal: Average percent removal during the three days.

3) Differential increment %removal: percent improvement of removal each depth group.

Table 4.3 shows that the percentage of fecal coliforms removal is; up to 13 % at depths of

up to 25 cm, up to 50 % at depths of up to 50 cm and up to 80.30 % at depths up to 100

y = -0.0043x2 + 1.4295x - 14.318 R² = 0.9614

0

20

40

60

80

100

0 20 40 60 80 100 120 140 160 180 200 220

Ave

rage

% r

em

ova

l of

FC

Depth of Filter


30

cm. It is also shown on Table 4.3 that the differential increment removal at effective

depths 50 cm and 75 cm are 28.27 % and 28.90 % respectively and thus both together

accounting for 60 % of removal of fecal coliforms in the system.

Figure ‎4.11: Petri dishes for one of the fecal coliforms tests

Figure 4.11 presents perti dishes - for fecal coliform test - after being incubated in the

laboratory so as the fecal coliform colonies can be counted.

Figure ‎4.12: Surface layer of filter before infiltration (right) and after (left)

Figure 4.12 above at the right shows the upper layer of the sand filter system before storm

water being passed to the system, while the left shows the upper surface after storm water

being passed through where a formed layer of impurities and dirt can been seen.


31

4.2.2 Suspended solid removal along the three days of infiltration

The percent of removal of suspended solids in each day of the three days of infiltration

versus sand filter depth is summarized in the curves chart shown in Figure 4.13. Figures

4.14, 4.15 and 4.16 summarize the relation of the above variables – SS removal and

specified depths - for each single day of the three days respectively using bar charts

Figure ‎4.13: Percent removal of suspended solid along three days of infiltration

Figure ‎4.14: Percent of removal of suspended solid vs each depth in the first day

50%

60%

70%

80%

90%

100%

0 25 50 75 100 125 150 175 200

% P

erc

en

t R

em

ova

l of

susp

en

de

so

lid


1st Day

2nd Day

3rd Day

50%

60%

70%

80%

90%

100%



32

Figure ‎4.15: Percent of removal of suspended solid vs each depth in the second day

Figure ‎4.16: Percent removal of suspended solid vs each depth in the third day

The change of removal from depth to depth varies from day to day, but in general they

have a close pattern and there is no significant difference in the percentage of removal

between these three days with exception to the upper depths on the first day.

The concentration of suspended solid in the effluent of each sand filter depth versus sand

filter depth at each single day of the three infiltration days are presented in the Figures

4.17, 4.18 and 4.19.

50%

60%

70%

80%

90%

100%


50%

60%

70%

80%

90%

100%



33

Figure ‎4.17: Concentration of suspended solid effluents vs each depth in first day

Figure ‎4.18: Concentration of suspended solid effluents vs each depth in second day

Figure ‎4.19: Concentration of suspended solid effluents vs each depth in third day

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00


0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00

40.00

45.00

50.00


0.00

10.00

20.00

30.00

40.00

50.00

60.00



34

The concentration of suspended solids in each effluent at the first two depths or valves (at

depths of 12.5 and 25 cm) is a function of concentration of suspended solids in the

influent as shown in Figure 4.16 through 4.18. At later depths up to 100 cm (37.50 – 100

cm) the concentration of SS in the effluents are all close and less than 20 mg /lr. At depths

150 cm and 200 cm , concentration of SS in the effluents are in the same range and little

less than 10 mg / lr.

Data of the removal of suspended solids along the three days of infiltration are shown

below in Table 4.4 and Figure 4.20 where the average percent removal and differential

percent increment of removal - reflecting the percent of improvement of removal at each

depth- are presented.

Table ‎4.4: Analysis of effluent suspended solid along three days

Where:

1) Min. %removal: Minimum percent removal during the three days.

2) Max. %removal: Maximum percent removal during the three days.


4) Differential increment %removal: percent improvement of removal each depth.

5) Average concentration: Effluent average concentration for all three days.

Depth Min.

%removal 1

Max.

%removal 2

Average

%removal 3


%removal 4

Average

concentration 5

12.5 cm 53.7 66.3 58.33 - 42.33

25 cm 61.1 74.7 67.93 +9.6 32.66

37.5 cm 81.1 84.3 83.13 +15.2 17

50 cm 85.3 87 86.13 +3 14

75 cm 86.3 88.9 87.4 +1.27 12.67

100 cm 87 88.9 87.76 +0.36 12.33

150 cm 89 90.7 89.73 +1.97 10.33

200 cm 91 92.6 91.73 +2 8.33


35

Figure ‎4.20: Relationship between the depth of filter and the SS average % removal

Figure 4.20 shows the mathematical relation between the depth of filter and the average

percent removal of suspended solid, which can represented as follow:

𝑓(x)={

Where x: depth in cm and 𝑓(x) the percent removal of SS

Referring to Table 4.4, it is noted that at depth up to 37.5cm the average removal of

suspended solids is 83.13 %. Thus, this depth represents the effective depth for the

removal of suspended solids. It is also noticed that there is no significant decrease in

suspended solids concentrations through the depths ranging from 37.5cm to 100 cm with

an average concentration of 14 mg/l, and similarly at depths 150cm to 200cm with an

average concentration of 9.33 mg/l.

As shown from the analysis illustrated in Table 4.4, the specified depths can be rearranged

in groups basis as the average concentration and removal of suspended solids have a

certain pattern with the specified depths. Thus, the change in performance can be better

understood and concluded.

y = 0.992x + 44.997

y = 0.045x + 83.058

50

55

60

65

70

75

80

85

90

95

100

0 20 40 60 80 100 120 140 160 180 200

Ave

rage

% r

em

ova

l of

SS

Depth of Filter (cm)


36

Table ‎4.5: Depth grouping for results analysis of effluent suspended solid

Depth range Average

%removal 1

Differential

increment

%removal 2

Average

concentration 3

(mg/l)

Suspended solid

removal 4(mg/l)

12.5 cm 58.33 58.33 42.33 58.67

25 cm 67.93 9.6 32.66 68.34

(37.5-100) cm 86.11 18.18 (17-12.33) ≈ 14 87

150 cm 89.73 3.62 10.33 90.67

200 cm 91.73 2 8.33 92.67

Where:


2) Differential increment %removal: percent improvement of removal each depth group.

3) Average concentration: Effluent average concentration for all three days.

4) Suspended solid removal: Concentration of suspended solid that have been removed.

Table 4.5 shows that the effective depth is at depth 25cm in the first layer having a

percent removal of 67.93%, while depths ranging from (37.5-100) cm there are no

significant suspended solids removal and the average SS concentration in their effluents

is 14 mg/l. At depths 150cm and 200cm the average concentration are 10.33mg/l and 8.33

mg/l respectively, and the percent of removal are 90% and 92% respectively.

The results confirms with literature reviewed in Chapter (2); Ellis (1984) and Khan

(1995) concluded that the chances of higher removal efficiency of impurities are greatly

increased when increasing sand filter depth. Hsieh and Davis (2005) studies showed that

the percent removal of suspended solids by sand filter reaches 99%, and Khan (1995)

study showed that the percent removal reaches 99% for fecal coliforms at depth 150cm.

4.3 Effect of different concentrations of fecal coliforms

The study investigated the effect of different F.C concentrations in the influent storm

water on the system's performance and its ability in term of F.C removal.

Experiment was done after washing the media and removing the layer of dirt accumulated

over the upper surface of the sand media. A specific and measured quantity of wastewater

– collected from one of the wastewater pumping stations, was added. The added quantity

contained at least two millions of fecal coliforms per 100 ml and thus F.C concentration

in the influent storm water reached 36000 col/100ml. The system then was operated


37

having these parameters or inputs and results were recorded. Results of this experiment is

presented and illustrated in Table 4.6as well as Figures 4.21 and 4.22.

Table ‎4.6: Percent removal of fecal coliforms at influent 36000 col./100 ml

Influent fecal coliforms = 36000 col./100 ml

Filter

Depth

Effluent fecal

coliforms (col./100 ml)

% fecal coliforms

removal

12.5 cm 24000 67.6%

25 cm 9000 87.8%

37.5 cm 8000 89.2%

50 cm 8000 89.2%

75 cm 5000 93.2%

100 cm 5000 93.2%

150 cm 0 100.0%

200 cm 0 100.0%

Figure ‎4.21: Percent removal of fecal coliforms at influent 36000 col./100 ml

Table 4.6 shows that increasing the F.C concentration ( i.e to 36000 col./100 ) ml in the

influent storm water has a positive impact on the rate F.C removal for the upper layers -

50%

60%

70%

80%

90%

100%

110%

0 25 50 75 100 125 150 175 200

% P

erce

nt

Rem

ova

l of

feca

l co

lifo

rm



38

compared with the previously obtained results for three days of continuous filtration;

where at depth of 12.5 cm, recorded removal of F.C was 12000 col./100ml of fecal

coliforms accounting for a total removal of 67.6% ; at depth of 25 cm, recorded removal

was 27000 col/100ml accounting for total F.C removal of 87.8%. Those results reflect a

significant difference from what was obtained in the previous experiments of continues

three days of infiltration as the recorded average F.C removal was 9.27 % and 12.97 at

depths 12.5 and 25 cm respectively.

Despite the high percentage removal and results discussed earlier, there were significant

concentrations of fecal coliforms at depth ranging from (37.5cm to 100cm) with an

average concentration of 6500 col./100ml and this figure is close to previous results

obtained from three days infiltration test with an average approximately 4000 col./100ml.

Figure ‎4.22: Depth percent removal of fecal coliforms at influent 36000 col./100 ml

As shown below in Figure 4.23; depths of filter deeper than 25 cm, effluents produced

have relatively low concentration of fecal coliforms (i.e. at depths 37.5 cm and 50cm, the

concentration of F.C is about 8000 FC/per 100 ml compared to F.C concentration in the

influent of 36000 col/100 ml). This improvement in the removal of F.C may be referred to

the nature of F.C. as it exists in the solid parts inside the storm water. Also, the sand filter

is efficient in pending these solid particles which includes high percent of FC.

Furthermore, it is clear that fecal coliforms are completely removed at depths beyond the

150 cm despite influent containing 36000 FC/100 ml.

50%

60%

70%

80%

90%

100%


Pe

rce

nt

FC r

em

ova

l

Filter Depths


39

It can be noticed also that at depths deeper than 150cm ranging from (150cm to 200cm)

there were a complete removal of fecal coliforms, and this - despite the high concentration

of fecal coliforms in the influent at this case - is identical with the previous results

obtained from three days infiltration.

Figure ‎4.23: Number of fecal coliforms (col./100ml) at influent 36000 col./100 ml

The experiment was repeated again but by passing influent storm water having a F.C

coliform concentration of 74000 Col. / 100 ml (twice the concentration in the previous

experiment) to the system. Similarly, a specific and measured quantity of wastewater was

added to reach this concentration, 74000 col. / 100 ml. Table 4.7 and Figure 4.24 shows

presents and illustrates the results obtained.

0.00

5,000.00

10,000.00

15,000.00

20,000.00

25,000.00

30,000.00


Feca

l Cal

ifo

rm C

on

cen

trat

ion

Filter Depth


40

Table ‎4.7: Percent removal of fecal coliforms at influent 74000 col./100 ml

Influent fecal coliforms = 74000

col./100 ml

Filter

Depth

Effluent fecal

coliforms (col./100

ml)

% fecal

coliforms

removal

12.5 cm 32000 56.8%

25 cm 14000 81.1%

37.5 cm 7000 90.5%

50 cm 7000 90.5%

75 cm 7000 90.5%

100 cm 3000 95.9%

150 cm 1000 98.6%

200 cm 0 100.0%

Figure ‎4.24: Percent removal of fecal coliforms at influent 74000 col./100 ml

Table 4.7 shows that increasing the F.C concentration in the influent to 74000 col./100

ml - compared to previously obtained results for three days of continuous filtration - has a

50%

60%

70%

80%

90%

100%

110%

0 25 50 75 100 125 150 175 200

% P

erce

nt

Rem

ova

l of

feca

l co

lifo

rm



41

positive impact on the rate of removal for the upper layers of the filter; where at depth of

12.5 cm, recorded removal of F.C was 42000 col./100ml of fecal coliforms accounting for

a total removal of 56.8% ; at depth of 25 cm, recorded removal was 60000 col/100ml

accounting for total F.C removal of 81.8%. Those results reflect a significant difference

from what was obtained in the previous experiments of continues three days of infiltration

as the recorded average F.C removal was 9.27 % and 12.97 at depths 12.5 and 25 cm

respectively.

Despite the high percentage removal and results discussed earlier, there were significant

concentrations of fecal coliforms at depth ranging from (37.5cm to 100cm) with an

average concentration of 5000 col./100ml and this figure is relatively close to previous

results obtained from three days infiltration test with an average approximately 4000

col./100 ml

Figure ‎4.25: Depth percent removal of fecal coliforms at influent 74000 col./100 ml

As shown in Figure 4.25; depths of filter deeper than 25 cm (i.e. at depths of 37.50 cm,

50 cm and 70 cm), effluents produced have relatively low concentration of fecal

coliforms; 7000 F.C / 100 ml compared to F.C concentration in the influent of 74000

col/100 ml). This improvement in the removal of F.C may be referred to the nature of

F.C. as it exists in the solid parts inside the storm water. Also, the sand filter is efficient in

pending these solid particles which includes high percent of FC.

50%

60%

70%

80%

90%

100%


Pe

rce

nt

FC r

em

aova

l

Filter Depth


42

Furthermore, it is clear that fecal coliforms are completely removed at depth of 200 cm

and not at 150 cm as what was obtained from the previous experiment (i.e. the F.C

concentration at the influent 36000 F.C / 100 ml). Thus, the effective depth in this

experiment is 200 cm.

Figure ‎4.26: Number of fecal coliforms (col./100 ml) at influent 74000 col./100 ml

It can be concluded from the two conducted experiments illustrated above (i.e. when

increasing the F.C concentration in the influent to 36000 F.C/ 100 ml and another increase

to 74000 F.C / 100 ml) that total removal of fecal coliform largely depends on the

concentration of F.C at the influent. The average percent removal of fecal coliforms at

depth 25 cm is 84.45 % and at deeper depths the differential removal becomes less and

less.

4.4 Effect of different concentrations of suspended solid

The study also investigated and examined the effect of increasing suspended solids in the

influent storm water on the system's performance and its ability in term of suspended

solids removal.

Experiment was done after washing the media and removing the layer of dirt accumulated

over the upper surface of the sand media. A specific and measured amount of soil was

added to reach a SS concentration of 1468 mg/l of storm water. The system then was

operated. Results of this experiment are presented and illustrated in Table 4.8 and Figure

0.00

5,000.00

10,000.00

15,000.00

20,000.00

25,000.00

30,000.00

35,000.00


Nu

mb

er

of

Feca

l Cal

ifo

rms

Filter Depth


43

4.27 as well.

Table ‎4.8: Percent removal of suspended solid at influent 1468 mg/l

Influent suspended solid= 1468 mg/l

Filter

Depth

Effluent suspended

solid (mg/l)

suspended

solid %removal

12.5 cm 250 83.0%

25 cm 79 94.6%

37.5 cm 20 98.6%

50 cm 20 98.6%

75 cm 17 98.8%

100 cm 15 99.0%

150 cm 15 99.0%

200 cm 12 99.2%

Table 4.8 shows that increasing the SS concentration (i.e to 1468 mg/l) in the influent

storm water has a positive impact on the rate SS removal for the upper layers - compared

with the previously obtained results for three days of continuous filtration; where at depth

of 12.5 cm, recorded removal of SS was 1218 mg/l accounting for a total removal of

83% ; at depth of 25 cm, recorded removal of SS was 1389 mg/l accounting for total SS

removal of 94.60 %. These results to some extent agree with results obtained from three

days of infiltration; similarly, the upper depths or filtration layers have significant impact

and role on the removal of suspended solids. The negative impact on the flow rate due to

filtration process accelerates the accumulation of contaminants on the upper surface of the

filter and thus accelerating the clogging in the body of the filter media.


44

Figure ‎4.27: Depth percent removal of suspended solid at influent 1468 mg/l

Figure ‎4.28: Depth percent removal of suspended solid at influent 1468 mg/l

As shown in Figures 4.27 and 4.28; depths of filter deeper than 25 cm, effluents produced

have relatively low concentration of suspended solids (i.e. at depth of 37.50 the

concentration at the effluent was 20 mg/l) - compared with the high concentration of SS in

70%

80%

90%

100%

0 25 50 75 100 125 150 175 200

% P

erc

en

t R

em

ova

l of

Susp

en

de

d s

oli

d


80%

90%

100%



45

influent storm water which was 1468 mg/l. The effect of the filter depth on the suspended

solids removal is thus insignificant; depths ranging from 37.50 to 100 cm had effluents

containing only 15 to 20 mg/l , and at depth 200 cm the SS concentration was 12 mg/l

(see Figure 4.29).

Figure ‎4.29: Concentration of suspended solid in the effluent at different depths

0.00

50.00

100.00

150.00

200.00

250.00

300.00


Co

nce

ntr

atio

n o

f su

spe

nd

ed

so

lid

Filter Depth

46

Chapter 5 Conclusions and Recommendations

5.1 Conclusions

As a result of this research project, the following points can be concluded:

1. This laboratory research studied and investigated the capability of sand filters to

purify storm water through using a 2 m sand filter. Two parameters were used in

this investigation; suspended solids and fecal coliforms. Finding, the sand filter

was capable of achieving a good results in term of suspended solids and fecal

coliforms removal.

2. Used sand filter was able to completely remove fecal coliforms at depth of 150 cm

and was able to produce effluent having acceptable concentration of suspended

solid at depth 75, less than 20mg/l.

3. Percent removal of fecal coliforms by infiltration using sand filter media increased

as the depth of the sand filter increased.

4. Using sand filter for the removal of suspended solid is effective and there is a

significant effect of increasing the filter depth.

5. About 80% of the removal of fecal coliforms occurred at depth 75cm, and about

83% percent removal of suspended solid occurred at depth 37.5cm.

6. High concentrations of suspended solids or fecal coliforms were not the major

factor in term of removal efficiency. At short term, it had a positive role in

increasing the percent of removal at upper depths of sand filter. At long term

however it had a negative impact as it accelerated the occurrence of clogging in

the filter.

47

5.2 Recommendations

Following this study there are a number of recommendations that are made forfurther

work:

1. It is recommended to use other parameters in the investigation to better measure

the percent removal achieved by sand filter such as (Metals, BOD, NH3…).

2. It is recommended to apply the experiment in large scale for example using tank

filled with media.

3. Through the work of laboratory tests, it is seemed the importance of the subject of

maintenance for sand filter, therefor it is recommended to giving this issue a

priority by bodies which responsible to operation such treatment facility .

48

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51

Appendix: Photos Show the Method of the

Work in the Laboratory

52

Cooper Reducing Bushings used for each depth valve

Collected sand filter sample

53

Sand filter sample location in local storm water infiltration basin

Fan used in testing apparatus

54

Testing apparatus System

Glass window in testing pipe 8"