PMSA Conference

Heger, Sick Tanks

1/20/14

1

SICK SEPTIC TANKS

Sara Heger

University of Minnesota

Training professionals since 1974 Designers, Installers, Maintainers, Service Providers,

Inspectors

Conduct research Current working on three grant projects

Work with homeowners and small communities

5 staff members

Presentation Overview

Evaluating the tank operating conditions

Evaluating source

Common problems/issues

Conditions at the tank

Can I install a riser?

Yes

Plastic

Ease

Watertight

Strength

Concrete

PMSA Conference

Heger, Sick Tanks

1/20/14

2

Tank Access

Lid in operable condition?

Evaluating the System & Source

User homeowner survey/troubleshooting form

Example on our website at: http://septic.umn.edu/formsandsheets/index.htm

Information:Number of people (adults, kids, teenagers, etc)

In-home businesses

Type of products used with laundry, dishwashing, hand-washing, general household cleaning

Use of prescription drugs/antibiotics

Current operating condition

Current operating condition Tank structural condition

PMSA Conference

Heger, Sick Tanks

1/20/14

3

Corrosion in the Tank

Hydrogen Sulfide

Lack of Venting

Check Piping

Splashing

Orange is Rust

Process of Troubleshooting Off look or smell to tank?

Effluent filter plugging up routinely?

Excessive ponding/surfacing?

Get list of medicines/cleaners

Run field analysis

Get lab analysis to determine how “sick” the tank is BOD and TSS

FOG only if commercial or a lot of FOG visible

Determine last date of tank pumping and amount of sludge and scum

Healthy Septic Tank• Scum and sludge normal• Some carryover to second compartment• Limited flocculent in clear zone

All Systems Need Healthy Bugs

Range

DO pH Temp SEPTIC TANK SHOULD SMELL “SEPTIC” WHEN

YOU OPEN THE LIDAnaerobic Digestion

ORGANICMATTER

BACTERIA GASES + HUMUS

CO2

CH4

H2SNH3

PMSA Conference

Heger, Sick Tanks

1/20/14

4

Septic OdorsOutside:

• Clear stack of obstructions

• Raise vent stack

• Charcoal filter on stack –careful as may freeze in winter

Inside:1. Frozen stack

2. Dry trap

3. Seals on grinder pumps in basement

Odor

Effluent odor in septic/pump tank Septic None Clean

Effluent odor after advanced treatment unit: Septic None Clean

Anaerobic Microbes

Anaerobic bacteria grow in absence of free oxygen,O2

Most anaerobic organisms are bacteria Anaerobic treatment processes split oxygen bound, Ex. SO4: →H2S, NO3 →N2

Common condition in: Septic tanks, Processing tanks, Constructed wetlands Other saturated environments

Anaerobes Cont’d

They are not able to get as much energy from their food

Advantages: Microbes that do not require oxygen are able to live in places

where aerobes cannot survive, such as the human gut, and many other places where oxygen is in low supply

For pathogenic microbes (those that cause disease), this ability is a huge advantage, allowing anaerobic pathogens to cause disease in areas of the body that are not exposed to oxygen

Testing Microbial Activity

Test COD versus BOD5

If COD significantly higher than BOD (more than double) – chemical oxidation of everything including chemicals

Have laboratory run BOD5 at various dilutions There will be no BOD demand at high levels if

inhibitory chemicals

Factors That Influence Anaerobic Digestion

pH

Chemicals

Highly variable flow patterns

Pharmaceuticals

Process wastewaters

Lack of tank maintenance

PMSA Conference

Heger, Sick Tanks

1/20/14

5

Environmental Effects on Microbes

Microbes need Temperature must be life-sustaining

Steady supply of food to maintain stable microbial population

pH needs to be controlled

Limited biocides (acid drain cleaner, antibiotics, etc

Dead microbes Stink

Are Black

Don’t move

Dissolved Oxygen (DO)

Concentration of O2 dissolved in water

DO low in septic tank <0.3 mg/L

DO >2 from advanced units

pH ranges for Microbes

Ideal Range in Wastewater

Low pH < 6.5

Ideal 7

High pH >7.2

pH pH is the negative log of the hydrogen ion

concentration

It can have a major impact on biological and chemical reactions

Neutral range best for microbial growth Typically 6.5 – 7.5 in our systems

Where Does It Come From?

Low pH: Acids Coffee, soda

Acid cleaners

High pH: Basic Ammonia

Cleaners

Dairy

PMSA Conference

Heger, Sick Tanks

1/20/14

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Temperature

Typical range: 48 – 70˚F

Typical value: 59˚F

Low end concernsMicrobes become dormant below 39°F

Nitrification impacted by temps below 50°F

High end concerns< 75o

Fats solidify

What Influences Temperature

Water temperature

Holding time

Air temperature Venting

BULKINGWhat is bulking?

Lightening of the sludge = emulsification

How do you know if bulking has occurred?Location of the mass

What is the impact on a system that has bulked?Solids [mass] overload

Chemical Reaction is StartingSludge and scum layers are thinning• Clear zone will become less obvious• Check color of solids – brown or yellow = chemical emulsification• May detect a chemical odor

Bulking Due to Chemicals• Homogeneous mixture• No clear zone• Solids carryover definite

Checking the Sludge Levels

Use sampling probe Should be three

distinct layers if functioning properly

Heavy accumulation means excess inputs

One uniform layer ~ excess chemical inputs?

PMSA Conference

Heger, Sick Tanks

1/20/14

7

Checking the Scum Levels

Thick layer indicates excess: Fat, Oil and Grease

Paper product over usage

No scum layerWater treatment devices

Chemical emulsification

Septic Tank Pumping Needed?

Should be pumped when total solids reach 25-33% of tank capacity.

If ‘A’ is less than 3”

If ‘B’ is less than 12”

Wastewater Quality Measures

BOD Biochemical oxygen demand

TSS Total suspended solids

O&G or FOG Fats, oils & grease

What is Domestic versus High Strength Wastewater (HSW)?

CIDWT glossary definition of HSW

1) Influent having BOD5 > 300 mg/L,

and/or TSS > 200 mg/L,

and/or fats, oils, and grease (FOG) > 50 mg/L entering a pretreatment component

2) Effluent from a septic tank or other pretreatment component that has: BOD5 > 170 mg/L,

and/or TSS > 60 mg/L,

and/or (FOG) > 25 mg/L and is applied to an infiltrative surface

HSW Impacts on Treatment

High levels lead to clogging

Reduce efficiency of treatment system

Block or plug distribution pipes

Seal off and plug voids in soil and filters

Neutral buoyancy solids do not settle stay in suspension in the tank “clear zone”

may carry over to next treatment step

PMSA Conference

Heger, Sick Tanks

1/20/14

8

Where Does BOD Come From?

Everything

Soda fountains

Soft serve ice cream

Alcohols

Food waste

Greasy foods FOG

BIOCHEMICAL OXYGEN DEMAND (BOD5 )

Domestic range: 110 - 250 mg/L

120 mg/L and 10 mg/L Over 600 mg/L

Total Suspended Solids Total Suspended Solids

(TSS) Solids that don’t pass

through filter Mixture of organic and

inorganic particles

Organic vs inorganic components Organic can be digestible Inorganic cannot be

digested

Total Suspended Solids(TSS)

Domestic Range: 44 -155 mg/L

Where Does TSS Come From?

Organic matter (garbage disposal)

Toilet paper

Lint

Dirt

Other solids Plastics

Feminine hygiene products

Fats, Oils, and Grease (FOG)

Degradable Animal or vegetable-based FOG Residential kitchens

Non-degradable Petroleum-based FOG Industry/automotive

repair Bath oils, moisturizing

cream, tanning oils

A degreaser (emulsifier) will move all FOG components through a system

PMSA Conference

Heger, Sick Tanks

1/20/14

9

System Impacts

Fats, Oil and Grease Add to septic tank scum layer

Clog pipes, treatment systems, drainfields

Collect and harden on surface, trap trash, plants and other materials

Cause foul odors and attract insect pests

Degreaser moves through tanks

FOG

Problematic Effluent Screens

The need for frequent cleaning is an indication of:Hydraulic

overloadingOrganic over

loadingToxic loading

Alarm

Alarm on Screen Present and working?

Prohibited specifically by ordinance Chemical treated water from pool or hot tub

Sump pump/tile line discharge

Roof runoff

Should be limited: Iron or other water filters

Dehumidifier discharge

High efficiency furnace discharge

Dripping faucets/”running toilets”

Other Sources of Water That Can Overload a System(and don’t need treatment)

Water Softener

Doesn’t require treatment

Impact:◦ Adds water◦ Reduces scum layer- grabs

it, takes into drainfield◦ Salt – can affect concrete

(tank)

Management –◦ Discharge to different

place old drainfield/cesspool

◦ Reduce recharge frequency

Mixing of Tank

Solutions Control usage Controlling loading

Timer control

Increased tank capacity

Effluent filter

Reasons Leaks/clean water Peak use

Multiple shower heads

Pumping to tank Elevation difference

Upstairs laundry or large bath tub

PMSA Conference

Heger, Sick Tanks

1/20/14

10

Don’t Forget the Pump Tank

Maintenance needed?

Accessible

Alarm operational

Wiring in good shape

Tank Start-up with New Systems

Toxic tank Cleaning chemicals

Construction chemicals

Other Outcomes First time on septic - education on use

Understanding the need for maintenance

QUESTIONS? MORE INFORMATION

septic.umn.edu