EutrophicationEutrophication is a term describingthe enrichment of waters withnutrients. It often results inexcessive growth of weed and algae.Microorganisms decompose theorganic matter in the polluted water Stock defecate and urinate into water bodiesand their activity increases theuptake of dissolved oxygen. This reduces the amount ofdissolved oxygen available to otheraquatic organisms and maysubsequently cause their death. Nutrient enrichment can lead to algal blooms
Sewage PollutionRaw or partially treated sewage is acommon water pollutant. Sewage pollution results from the disposal of household and industrial wastes into Raw sewage, UK rivers, lakes, and seas. Most communities apply some treatment to raw sewage prior to discharge from point sources, but even treated sewage can be high in nutrients. Sewage is a source of pathogens (disease- causing agents). During floods, human waste may mix with drinking water and increase the risk of water-borne diseases such as cholera. Flood waters, Bangladesh
Sediment PollutionSediment pollution comes from agricultural land,forest soils exposed by logging, overgrazedrangelands, strip mining, and construction. Suspended sediments increase turbidity and reduce light penetration. When they settle out, they smother aquatic organisms and reduce available habitat. Increased sediment loads may choke waterways and cause sediment buildup behind dams and in reservoirs. Earthworks and quarrying increase sediment runoff Stream erosion and sediment runoff
Detecting Water Pollution 1The extent of water pollution can bedetermined in many ways: The nutrient loading can be assessed by measuring the BOD (the Biochemical (or Biological) Oxygen Demand). Oxygen meter Electronic probes and chemical tests can identify the absolute levels of various inorganic pollutants (nitrates, phosphates, and heavy metals). Stirrer Probe has a membrane across which oxygen diffuses
Detecting Water Pollution 2The presence (or absence) of indicatorspecies can give a biological indicationof the pollution status of the waterway.Different species have differenttolerance levels to varying levels ofpollution. Clean water communitiesare typically diverse, and species with High diversity communityhigh oxygen requirementspredominate.Communities in polluted or turbidstreams are much less diverse and aredominated by species that are tolerantof low oxygen levels and sluggish waterflows. Low diversity community
Sewage TreatmentSewage includes all waste water that has been usedby a household or industry. It does not include stormwater from road and property runoff, which is usually diverted directly into waterways.Waste water treatment plant. Trickling filters are Sewage pipes discharging into a holding tank pictured in the foreground.
Processing SewageSewage usually undergoes severallevels of treatment (purification): Primary treatment uses mechanical processes, such as screening and settling, to remove suspended sand and silt. This forms the primary sludge. Secondary treatment uses microorganisms to decompose the suspended organic material in the waste water. The bacteria-laden solids settle out as sewage sludge. Sedimentation tank Disinfection (usually by chlorination) kills any bacteria and other pathogens before the waste water is discharged. Tertiary treatment using biological, chemical, and physical processes is required to remove nitrogen, phosphorus, heavy metals, and synthetic organic Aeration tank: activated sludge compounds.
Sewage Treatment Plant Primary Treatment Secondary Treatment Disinfection and Release 3 Primary sludge is aerated and aerobic 1 Screening, skimming, microbes oxidize and grinding of sewage organic matter Solid matter 4 Effluent is disinfected 2 settles out by chlorination and then releasedSludge Digestion 5 Remaining sludge is digested anaerobically, producing methane 6 Sludge effluent Sludge is removed and is dried7 disposed of in landfill or on agricultural land
Sewage Treatment Plant Primary Treatment 1 Screening, skimming, and grinding of sewage 2 Solid matter settles out Sewage Primary sedimentation tank Primary sludge Primary sludge
Sewage Treatment Plant Secondary Treatment 3 Primary sludge is aerated and aerobic microbes oxidize organic matter. Trickling filter Primary sludge Settling tank Activated sludge Aeration tank Secondary sludge
Sewage Treatment Plant Disinfection and Release 4 Effluent is disinfectedChlorinator by chlorination and then released. Effluent
Sewage Treatment PlantSludge Digestion Primary sludge Secondary sludge Anaerobic 5 Remaining sludge is sludge digester digested anaerobically, producing methane. 7 Sludge is removed and disposed of in landfill or on agricultural land. 6 Sludge effluent is dried Drying bed