Environmental Effects of Wastewater use in Agriculture 4th Regional SUWA , Peru

A combination of one or more of:

- domestic effluent consisting of blackwater (excreta, urine and faecal sludge) and greywater (kitchen and bathing wastewater);

- water from commercial establishments and institutions, including hospitals;

- industrial effluent, stormwater and other urban run-off;

- agricultural, horticultural and aquaculture effluent, either dissolved or as suspended matter

(definition adapted from Raschid-Sally and Jayakody, 2008)

“Sick Water” Definition of Wastewater

UNEP wastewater management program – delivered through the GPA (Global Program of Action for the Protection of the Marine Environment from Land-based Activities);

Oceans, seas, islands and coastal areas form an integrated whole that is essential component of the Earth’s ecosystem and is critical for global food security and for sustaining economic prosperity and the well-being of many national economies

Other Pragmatic Considerations:

• 70% mega-cities are coastal

38% global population live on the coast

Many more come to the coast as

visitors , or economic opportunities ……

UNEP/GPA- Area of focus:

• Nutrients

• Marine Litter

• Wastewater

Open ocean

25%

Terrestrial

38%

Estuaries

12%

Coastal

38%

Seagrass/

algae beds

11%

Coral reefs 1%

Shelf

13%

Contribution of Coast and Ocean

in Global GDP

• Wastewater (raw, diluted or treated) is a resource of increasing global importance, particularly in urban and peri-urban areas due to growing wastewater volume,

• 10% percent of the world’s population would starve if they didn’t have access to food grown that way

• 20 million hectares in 50 countries are irrigated with raw or partially treated wastewater.

• The use of greywater is growing in both developed and less-developed countries – it is culturally more acceptable in some societies

• Without proper management, wastewater use poses serious risks to human health and environment

• With proper management, wastewater use can contribute significantly to sustaining livelihoods, foods security and the quality of the environment

Why bother about wastewater?

Sewage systems are lacking, under-dimensioned or decayed

Wastewater management….a big challenge

UNEP/GEF WIO-LaB Project 6

Wastewater………a global issue?

Simplified scheme of agricultural wastewater use & effects on environment (adapted from WHO Guidelines)

WW treatment plan

(in developing countries)

Evaporation

Aquifer

Consumer

Crops

Cattle

Water

Sewage Industri

al

discharg

e

Sewage system

Aquaculture

Aquatic

plants

Storage

dam

Infiltration

Aquatic

plants

Irrigation

channels

Infiltration

Water + salts

Soils

(retains metals, organic matter &

phosphorus) Compounds &

water absorption

by plants

Sprinkler

s

Cattle

consuming

irrigated crops

Irrigation

drainage

Lake

UNEP/GEF WIO-LaB Project 8

Dead zones are spreading………

• Dead zones are now thought to affect more than 245 000km2 of marine ecosystems, predominantly in the northern hemisphere

(Diaz and Rosenberg, 2008)

- Water security - Ecology - Ecosystem Services - Biodiversity

Impacts of wastewater on……

• Loss of food security • Loss of fisheries, livelihoods • Loss of blue carbon sinks • Economic loss :

• Healthy reefs can produce up to 35 tons of fish/km2/year

Impacts on climate Change

• Wastewater generates methane (21 times more powerful than

CO2) and nitrous oxide (310 time more powerful than CO2).

• CH4 & NO2 will rise 25% and 50% respectively in just a decade

• Nutrients increase acidification of freshwater

But, wastewater is a resource…

Already 10% of the world Population supplied with food grown using WW (Mexico, California, Cambodia), Water scarcity

Water pollution

Source of nutrients

Available all year round

Where is it most needed?

a) Innovative water technology

• Reduce the discharge of WW r, treat & re-use

b)Inventive governance &

management • Intelligence water use: Different

water uses need different water Quality

Trends in industrialized countries reversed but are on the increase in developing countries

Shortcutting the trends…..a must

A need for decentralised Technologies ....

• Septic Tanks, Constructed Wetlands, Composting Toilets,

Biodigestor, Anaerobic Filter, Duckweed Lagoons

• Collection, treatment, and final disposition of the WW on/or close to the

location;

• Useful in treating wastes from residences, households, small villages,

isolated communities, etc.

Advantages for decentralized systems:

Economy of structural arrangements such as transportation,

reservation and elevation;

Possibility for reuse of the effluent and potentiality for aquifer

recharging;

A problem in a unit doesn’t collapse the whole system;

Development of the local potentialities: small systems can be

designed, built and managed by local professional, improving the

local economy.

Type

Kind of treatment Kind of WW treated Advantages Disadvantages Nutrients removal

Septic Tank sedimentation, flotation

and digestion

Domestic wastewater

(communities until 100

inhabitants)

Simple, durable, easy

maintenance, small

area required

Low treatment

efficiency, necessity of a

secondary treatment,

effluent not odorless

COD, BOD, TSS;

grease.

Subsurface Flow

Constructed

Wetlands

biological and physical

processes

Domestic and agricultural

wastewaters; small

communities; tertiary

treatment for industries.

Low or no energy

requirements; Provide

aesthetic, commercial

and habitat value.

system clogging;

recommended as a

secondary treatment,

large areas required;

TSS; COD; TN;

TP.

Composting Toilets unsaturated and aerobic

conditions provide

biological and physical

decomposition

human excreta, toilet

paper, carbon additive,

food waste

Resulting "humus"

used as a resource;

conservation of water

resources; recycling of

nutrients.

If not well sized and

maintained can be a

environmental problem

and a threat for human

being, due to its

contaminant potential

Volume reduced

from 10 to 30%;

pathogens.

Biogas Digestor Sedimentation,

flotation and digestion

human excreta, animal and

agricultural wastes

Recycling of resource;

gas produced is used

for cooking and

lighting

Biogas plants can be

expensive to build and

difficult to operate. Poor

maintenance leads to loss

of gas production and

blockage of the digester

tank with solids.

Similar to septic

tanks systems; The

long period of

storage can also

remove some

pathogens.

Anaerobic Filter anaerobic

degradation of

suspended and

dissolved

solids

pre-settled

domestic and

industrial

wastewater of

narrow

COD/BOD ratio

simple and fairly

durable if well

constructed and

wastewater has been

properly pre-treated,

high

treatment efficiency,

little permanent space

required

costly in construction

because of special filter

material, blockage of

filter

possible, effluent smells

slightly despite high

treatment efficiency

BOD, TDS, TSS

Duckweed Based

WW Stabilizations

Ponds

sedimentation,

anaerobic degradation

and sludge stabilization

Domestic and agricultural

wastewater;

No clogging risk; High

nutrient removal rates

Necessity of large areas;

necessity of constant

harvesting; unsuitable in

very windy regions.

BOD, SS, TN, TP,

metals

Septic Tank

• The aim of primary treatment is to separate out heavy constituents and particularly light constituents from the sewage.

• Due to its low treatment efficiency in terms of nutrient removal, a secondary treatment is recommended to polish the final effluent.

• This system consists of a closed, often prefabricated tank and is usually applied for primary sewage treatment. The treatment consists of sedimentation, flotation and digestion procedures.

• Septic tank is designed to receive all kinds of domestic wastes (kitchen, domiciliar laundries, washrooms, latrines, bathrooms, showers, etc) and it is economically viable to attend to 100 inhabitants.

Constructed Wetland • Constructed Wetlands are man-made systems which aims to simulate

the treatment processes in natural wetlands by cultivating emergent plants e.g. reeds (Phragmites), bulrushes (Scirpus), and cattails (Typha) on sand, gravel, or soil media.

• Constructed wetlands can serve the same small communities as natural wetlands and can be incorporated into the treatment systems for larger communities as well;

• They are subdivided, basically, into two wide groups:

(i) Surface Flow (the water or sewage flows through the soil surface); and

(ii) Subsurface Flow. (Vertical and Horizontal Flow)

Subsurface Vertical Flow Constructed Wetland (SVFW)

• In SVFW the wastewater is loaded onto the planted filter bed’s surface. The pollutants are removed or transformed by microorganisms that are attached to the filtersand and the plants’ root system.

• Due to the biofilm presents in the filter material, and high Oxygen concentration in the system, vertical flow systems have been applied for both BOD5 and SS removal and nitrification promotion;

• However, it is important ensure that the filter is not saturated or covered with water in order to secure a high oxygen level in the filter.

Subsurface Horizontal Flow Constructed Wetland (SHFW)

• In SHFW the sewage is uniformly fed in the inlet work and due to a longitudinal slight slope (~1%) the liquid flows through the pores of the filter bed until it reaches the outlet work.

• SHFW usually provide high treatment effect in terms of removal of organics (BOD5, COD) and suspended solids (SS). The removal of nitrogen and phosphorus is lower but comparable with conventional treatment technologies which do not include special nutrient removal step.

Composting Toilets

• A composting toilet system contains and processes excrement, toilet paper, carbon additive, and sometimes, food waste.

• As a nonwater-carriage system, a composting toilet relies on unsaturated conditions where aerobic bacteria break down waste.

• When exposed to an unfavorable environment for an extended period of time, most pathogenic microorganisms will not survive. However, caution is essential when using the compost end-product and liquid residual in case some pathogens survive.

• The composting unit must be constructed to separate the solid fraction from the liquid fraction and produce a stable, humus material with less than 200 MPN per gram of fecal coliform.

• If sized and maintained properly, a composting toilet breaks down waste 10 to 30% of its original volume.

Biogas Digestor

• Biogas latrines and communal biogas plants are, in principle, a more advanced form of the septic tank system.

• When human excreta is combined with animal and agricultural wastes and water, it will give off gas as it decomposes.

• The mix of gases produced is called ‘biogas’ which can be used for cooking and lighting.

• Biogas plants typically store

the wastes for about 30 days which can remove some of the pathogenic organisms but by no means all.

Anaerobic Filter

• Anaerobic filters are used for wastewater with a low content of suspended solids (e.g. after primary treatment in septic tanks) and narrow COD/BOD ratio. Biogas utilisation may be considered in case of BOD > 1.000 mg/l.

• The anaerobic filter, also known as fixed bed or fixed film reactor, includes the treatment of non-settleable and dissolved solids by bringing them in close contact with a surplus of active bacterial mass.

• The larger the surface for bacterial growth, the quicker is the digestion.

Duckweed-Based Wastewater Stabilizations Ponds

• In general, duckweed ponds are used to treat domestic or agricultural wastewaters.

• Lemnaceae have the greatest capacity in absorbing macro-elements (e.g. nitrogen, phosphorus, potassium, calcium, sodium and magnesium among others);

• Effluents with both a high BOD and nutrient load may require adequate primary treatment to reduce the organic load.

• Plants must be harvested regularly in order to prevent dead plants forming bottom sludge.

Ecological Sanitation (EcoSan)

• Ecological Sanitation is a decentrilised sanitation system that understands human excreta, organic wastes and wastewater as a resource (not as a waste) with high potential for reuse and recycling.

• EcoSan systems enable a complete recovery of nutrients in household wastewater and their reuse in agriculture. They also help preserve soil fertility and safeguard long-term food security. Moreover, they minimise the consumption and pollution of water resources.

Ecological Sanitation (EcoSan)

Stages (or Phases)

Waste segregation and possible utilization options. (UNESCO/IHP & GTZ, 2006)

CH4

CO2

Electricity generator by Biogas

Food

Methane Combustion= CO2

Swine waste

Duckweeds Lagoon

http://www.winton.com.br/imagens/fotosx/cod2784.jpg

Targeted and sustained investments are necessary to:

-Reduce volume and extent of water pollution -Capture water once polluted

-Treat polluted water for return to environment -Safely reuse and recycle ww conserving water & nutrients

-Provide a platform for the development of new and innovative technologies & management practices social, economic and environmental dividends

exceeding original investments

Conditions for success:

A. Tackle immediate consequences

• Adopt a multi-sectoral approach

• Use a cocktail of innovative approaches

• Innovative financing

B. Thinking must be long-term: • plan wastewater management against

future scenarios.

• Solutions must be socially and culturally appropriate, as well as economically and environmentally viable into the future.

• Education must play a central role

Conditions for success:

From the Sick Water report

THANK YOU