Reclamation and Reuse of Sewage Waste Water

RECLAMATION AND REUSE OF SEWAGE WASTE WATER

What is Wastewater Reuse?

The U.S. Environmental Protection Agency (EPA) defines wastewater reuse as, "using wastewater or reclaimed water from one application for another application. A common type of recycled water is water that has been reclaimed from municipal wastewater (sewage)."

Reasons for Wastewater Reuse:

The most common reasons for establishing a wastewater reuse program is to identify new water sources for increased water demand and to find economical ways to meet increasingly more stringent discharge standards.

Types of Reuse

• Urban Reuse-the irrigation of public parks, school yards, highway medians, and residential landscapes, as well as for fire protection and toilet flushing in commercial and industrial buildings.

• Agricultural Reuse-irrigation of non-food crops, such as fodder and fibre, commercial nurseries, and pasture lands. High-quality reclaimed water is used to irrigate food crops.

• Recreational Impoundments-such as pond sand lakes.

• Environmental Reuse-creating artificial wetlands, enhancing natural wetlands, and sustaining stream flows.

• Industrial Reuse-process or makeup water and cooling tower water.

 

Technical Description

One of the most critical steps in any reuse program is to protect the public health, especially that of workers and consumers. To this end, it is most important to neutralize or eliminate any infectious agents or pathogenic organisms that may be present in the wastewater. For some reuse applications, such as irrigation of non- food crop plants, secondary treatment may be acceptable. For other applications, further disinfection, by such methods as chlorination or ozonation, may be necessary.

Application of Treated Wastewater

Agricultural Irrigation

• Crop irrigation

• Commercial nurseries

Landscape Irrigation

• Parks

• School yards

• Highway medians

• Golf courses

• Cemeteries

• Residential

Industrial Recycling and Reuse

• Cooling water

• Boiler feed

• Process water

• Heavy constructionib

Recreational / Environmental Uses

• Lakes & ponds

• Marsh enhancement

• Stream-flow augmentation

• Fisheries

Non-Potable Urban Uses

• Fire protection

• Air conditioning

• Toilet flushing

Potable Reuse

• Blending in water supply reservoirs

• Pipe-to-pipe water supply

• Constituents to be checked in Reclaimed Water.

Conventional (measured in mg/L; used in designing conventional WWTPs)

• TSS

• BOD; COD

• TOC

• Nitrogen (Ammonia; Nitrate; Nitrite)

• Phosphorus

• Microorganisms: Bacteria; Viruses; Protozoan cysts

Non-Conventional (to be removed or reduced by advanced treatment processes)

• Refractory organics

• VOC

• Surfactants

• Metals

• TDS

• Problems associated with Wastewater Reuse

Heavy Elements

• Public Health - nervous system disorders, mutagenesis, teratogenesis, carcinogenesis

• Bioaccumulation (food chain on crops and animals)

Surface water pollution

• Environmental Impact - acute and chronic toxicity for plant and animal life, chronic degradation effect on soil

• Nutrients (N & P)

 Public Health - blue-baby syndrome (from _NO3)

• Infiltration into potable water supplies

Environmental Health – Eutrophication, crop yield effects (+ive& -ive)

• Surface water pollution

• Irrigation practices

• Dissolved Solids (salinity)

Environmental Health

• Induce problems for the crops' yield selection and quantity

• Accumulation in soil

Effect on soil permeability

• Clogging drip-irrigation systems

• Emerging Pollutants

Public Health

• Acute and chronic health effects - effect on growth, reproduction problems

• Groundwater contamination

• Nitrate contamination on private drinking wells

• Antibiotics

Lower effectiveness of antibiotics if irrigation of fodder is involved

• Odour

• Public health of neighbouring communities

• Aesthetic concern - Reduced land values

Concerns with industrial processes

• Scaling

• Corrosion

• Biological growth & fouling

• Reclaimed wastewater can be safe for agricultural irrigation

• Reduce the pathogen levels

• Avoid direct contact of crops with reclaimed wastewater

• Restrict the type of crops irrigated

• Different treatment for safe irrigation of different crops:

• For tree nurseries, pastures, industrial crops

• Secondary treatment & detention in surface reservoirs

• Tertiary treatment (i.e. AS & Sand Filtration)

• For edible crops (uncooked)

• Tertiary treatment followed by soil aquifer treatment (or advanced)

Wastewater Reuse Advantages and Disadvantages

Advantages

• This technology reduces the demands of potable sources of freshwater.

• It may reduce the need for large wastewater treatment systems, if significant portions of the waste stream are reused or recycled.

• The technology may diminish the volume of wastewater discharged, resulting in a beneficial impact on the aquatic environment.

• Capital costs are low to medium for most systems and are recoverable in a very short time; this excludes systems designed for direct reuse of sewage water

• Operation and maintenance are relatively simple except in direct reuse systems where more extensive technology and quality control are required.

• Provision of nutrient-rich wastewaters can increase agricultural production in . water-poor areas.

• Pollution of rivers and groundwater may be reduced.

• Lawn maintenance and golf course irrigation is facilitated in resort areas.

• In most cases, the quality of the wastewater, as an irrigation water supply, is superior to that of well water.

Disadvantages

• If implemented on a large scale, revenues to water supply and wastewater utilities may fall as the demand for potable water for non-potable uses and the discharge of wastewaters is reduced.

• Reuse of wastewater may be seasonal in nature, resulting in the overloading of treatment and disposal facilities during the rainy season; if the wet season is of long duration and/or high intensity, the seasonal discharge of raw wastewaters may occur.

• Health problems, such as water-borne diseases and skin irritations, may occur in people coming into direct contact with reused wastewater.

• Gases, such as sulphuric acid, produced during the treatment process can result in chronic health problems.

• In some cases, reuse of wastewater is not economically feasible because of the requirement for an additional distribution system.

• Application of untreated wastewater as irrigation water or as injected recharge water may result in ground.