SourcesSources of wastewater include the followingdomestic or household activities:Ø Human excreta (feces and urine) often mixed with used toilet paper or wipes; this is known as black water if it is collected with flush toiletsØ Washing water (personal, clothes, floors, dishes, cars,etc.), also known as grey water or sullageØ Surplus manufactured liquids from domestic sources(drinks, cooking oil, pesticides, lubricating oil, paint, cleaning liquids, etc.
)Ø Activities producing industrialwastewater:Ø Industrial sitedrainage (silt, sand, alkali, oil, chemicalresidues);Ø Industrial cooling waters (biocides, heat, slimes, silt)Ø Industrial processing watersØ Organic or biodegradable waste, including waste from hospitals, abattoirs, creameries, and food factories.Ø Organic or non bio-degradable waste that isdifficult-to-treat from pharmaceutical or pesticide manufacturingØ Extreme pH waste from acid and alkali manufacturingØ Toxic waste from metal plating, cyanide production, pesticide manufacturing, etc.Ø Solids and emulsions from paper mills, factories producing lubricants or hydraulic oils, foodstuffs, etc.
)Ø Water used in hydraulicfracturingØ Produced water from oil & natural gas productionØ Other activities or events:Ø Urban runoff from highways, roads, carparks, roofs, sidewalks/pavements (contains oils,animal feces, litter, gasoline/petrol, diesel or rubber residues from tires, soapscum, metals from vehicle exhausts, de-icing agents, herbicides and pesticides from gardens,etc.)Ø Agriculturalpollution, direct and diffuseØ Wastewater can be diluted or mixed with other types ofwater by the following mechanisms:Ø Seawater ingress (high volumes of salt and microbes)Ø Direct ingress of river waterØ Rainfall collected on roofs, yards, hard-standings, etc.(generally clean with traces of oils and fuel)Ø Groundwater infiltrated into sewageØ Mixing with other types of wastewater or fecal sludge PollutantsThe composition of wastewater varies widely.This is a partial list of pollutants that may be contained in wastewater: Chemical or physical pollutantsØ Heavy metals, including mercury, lead, and chromiumØ Organic particles such as feces, hairs, food, vomit, paper fibers, plant material, humus, etc.;Ø Soluble organic material such as urea, fruit sugars, soluble proteins, drugs, pharmaceuticals, etc.
;Ø Inorganic particles such as sand, grit, metal particles, ceramics, etc.;Ø Soluble inorganic material such as ammonia, road-salt, sea-salt, cyanide, hydrogen sulfide, thiocyanates, thiosulfates, etc.;Ø Macro-solids such as sanitary napkins, nappies/diapers, condoms, needles, children’s toys, dead animals or plants, etc.;Ø Gases such as hydrogen sulfide, carbon dioxide, methane, etc.;Ø Emulsions such as paints, adhesives, mayonnaise, hair colorants, emulsified oils, etc.;Ø Toxins such as pesticides, poisons, herbicides, etc.Ø Pharmaceuticals and hormones and other hazardous substancesØ Thermal pollution from power stations and industrial manufacturersØ Biological pollutantsIf the wastewater contains human feces, as is the case for sewage, then it may also contain pathogens of one of the four types:Ø Bacteria (for example Salmonella, Shigella, Campylobacter, Vibrio cholerae),Ø Viruses (for example hepatitis A, rotavirus, enteroviruses),Ø Protozoa (for example Entamoebahistolytica, Giardia lamblia, Cryptosporidiumparvum) andØ Parasites such as helminths and their eggs (e.g.
Ascaris (roundworm), Ancylostoma (hookworm), Trichuris (whipworm));Ø It can also contain non-pathogenic bacteria and animalssuch as insects, arthropods, small fish. Quality indicatorsWastewaterquality indicatorsSince all natural waterways contain bacteriaand nutrients, almost any waste compounds introduced into such waterways will initiatebiochemical reactions (such as shown above). Those biochemical reactions createwhat is measured in the laboratory as the biochemicaloxygen demand (BOD). Such chemicals are also liable to bebroken down using strong oxidizing agents and these chemical reactions createwhat is measured in the laboratory as the chemical oxygendemand (COD). Both the BOD and COD tests are ameasure of the relative oxygen-depletion effect of a waste contaminant. Bothhave been widely adopted as a measure of pollution effect.
The BOD test measures the oxygen demand of biodegradable pollutants whereas the COD test measures the oxygendemand of oxidizable pollutants.Any oxidizable material present in an aerobic natural waterway or in anindustrial wastewater will be oxidized both by biochemical (bacterial) or chemical processes. The result is thatthe oxygen content of the water will be decreased. TreatmentWastewatertreatmentAt a global level, around 80% of wastewaterproduced is discharged into the environment untreated, causing widespread water pollution.4:2There are numerous processes that can be usedto clean up wastewaters depending on the type and extent of contamination.Wastewater can be treated in wastewater treatment plants which include physical, chemical and biologicaltreatment processes. Municipal wastewater is treated in sewage treatmentplants (which may also be referred to as wastewatertreatment plants). Agricultural wastewater may be treated in agriculturalwastewater treatment processes, whereas industrial wastewater istreated in industrialwastewater treatment processes.
For municipal wastewater the use of septic tanks and other On-Site Sewage Facilities (OSSF) is widespread in some rural areas, for example servingup to 20 percent of the homes in the U.S.5One type of aerobic treatment system is the activated sludge process, based on the maintenance and recirculation of acomplex biomass composed of micro-organisms able to absorb and adsorb the organic matter carried in the wastewater. Anaerobicwastewater treatment processes (UASB, EGSB) are also widely applied in the treatment of industrialwastewaters and biological sludge. Some wastewater may be highly treated andreused as reclaimed water. Constructedwetlands are also being used. DisposalIndustrial wastewater effluent withneutralized pH from tailing runoff in Peru.
In some urban areas, municipal wastewater iscarried separately in sanitary sewers and runoff from streets is carried in storm drains. Access to either of these systems is typically througha manhole.During high precipitation periods a combinedsewer system may experience a combined seweroverflow event, which forces untreated sewage to flowdirectly to receiving waters. This can pose a serious threat to public health and the surrounding environment.Sewage may drain directly into major watersheds with minimal or no treatment but this usually hasserious impacts on the quality of an environment and on the health of people. Pathogens can cause a variety of illnesses.
Some chemicals poserisks even at very low concentrations and can remain a threat for long periodsof time because of bioaccumulation in animal or human tissue.Wastewater may be pumped underground throughan injection well.