Water Pollutants and their Sources

River and Lake Pollutants Sewage, manure nitrogen, phosphorus pathogenic organisms biodegradable chemicals – consume O2 Fertilizers Pesticides, oil Toxic chemicals Sediments

Effects of Pollutants Oxygen depletion septic conditions change in biota destruction of certain species Biomagnification Restrictions on fish consumption Accumulation in sediments (benthic organisms) more turbid waters loss of habitats clog fish gills change in biota Foaming

Point sources Wastes that are collected in pipes or channels and discharged to a surface water with or without treatment Distinguished by source municipal sewage or wastewater industrial waste waters combined sewers and combined sewer overflows

Non-point sources Storm water runoff discharged at multiple points Varies substantially with use of the land runoff originates from agricultural urban suburban commercial special (e.g. golf courses) Minimal regulation

Oxygen-Demanding Material When organic substances are broken down in water, oxygen is consumed organic C + O2 → CO2 High oxygen levels necessary for healthy stream ecology trout require 5-8 mg/L dissolved oxygen (DO) carp require 3 mg/L DO aesthetic problem <1 mg/L

Oxygen-Demanding Material Pollutants measured by oxygen demand potential or total organic content biochemical oxygen demand (BOD) chemical oxygen demand (COD) total organic carbon (TOC) Sources municipal sewage -- agricultural wastes storm water -- leachate industrial wastes (e.g. pulp and paper, food processing, chemical processing)

Nutrients Phosphorus is typically the limiting nutrient in lakes, and algae growth is linked to phosphorus inputs Problems aesthetics taste and odor in drinking water can be toxic, especially to farm animals Disturbance in DO cycles

Nutrients Phosphorous Sources fertilizers detergents Phosphorous can exist in a variety of chemical forms, so total P in normally measured

Nutrients Nitrogen is often the limiting nutrient in ocean waters and some streams Nitrogen can exist in numerous forms, but nitrate (NO3-), nitrite (NO2-), ammonia (NH3) are most commonly measured Sources are primarily from fertilizers and acid deposition

Salts Dissolved solids, or salts, may be present as any number of ions cations: Na+, K+, Mg2+, Ca2+ anions: Cl-, SO42-, HCO3- Typically measures as total dissolved solids (TDS) Water classification freshwater <1500 mg/L TDS brackish water 1500 – 5000 mg/L saline water >5000 mg/L sea water 30-34 g/L

Salts Sources and concentration influences Effects minerals evaporative losses irrigation industrial discharges sea water intrusion Effects limits use for drinking crop damage/soil poisoning

Suspended Solids Organic and inorganic particles in water are termed suspended solids May be distinguished from colloids, particles that do not settle readily Measured by filtering a water sample, drying and weighing the filter

Suspended Solids Problems Sources sedimentation may exert oxygen demand primary transport mechanism for many metals, organics and pathogens aesthetic complicates drinking water treatment Sources storm water wastes erosion

Pathogenic Organisms Many organisms that cause human or animal diseases colonize the intestinal tract but can live for a period of time outside the body Carriers (who may or may not exhibit disease symptoms) excrete these intestinal tract organisms in very large numbers When water is contaminated by excreta, the organisms can be transmitted to those who contact the water

Pathogenic Organisms

Pathogenic Organisms

Toxic and Hazardous Substances Heavy metals Other inorganic elements Acids/bases Oxidants/reductants Chlorination by-products Combustion by-products Volatile organic compounds Petroleum Additives Pesticides

Volatile Organic Compounds Petroleum constituents: benzene and substituted benzenes prevalent in gasoline, diesel fuel, heating oil most easily transported, slow degradation, toxic

Volatile Organic Compounds Oxygenated gasoline additives added to gasoline to improve air quality very soluble, resistant to degradation, toxic attempt to solve one problem caused another (spills) Methyl tertiary butyl ether (MTBE)

Volatile Organic Compounds Chlorinated solvents C1 and C2 aliphatic widely used in degreasing, dry cleaning, extraction somewhat soluble, volatile, difficult to degrade

Hydrophobic Organics/ Chlorinated Aromatics Chlorinated Pesticides Polychlorinated dibenzodioxins (PCDDs) Polychlorinated biphenyls (PCBs)

Some Other Categories Trihalomethanes Explosives and Propellants Phenolics Aldehydes Organometallics Asbestos

Arsenic Occurs naturally in rock and soil Released to groundwater under some conditions Health effects include skin cancer, nervous system effects, and kidney disease Major problem in Bangladesh