Water Pollution

Part - II

Water pollution from Agriculture

• Fertilizer runoff causes water enrichment.• Animal wastes and plant residues in waterways

produce high BODs and high levels of suspended solids as well as water enrichment.

• Chemical pesticides used in agriculture may leach into the soil and from there into waterways.

• Soil erosion from fields and rangeland cause sediment pollution in waterways.

Water Pollution from Agriculture

What is going into the water from farm operations?

•Pesticides•Fertilizers•Manure•sediments

Municipal Water Pollution

What is going into the water from urban runoff?

• Salt from roadways• Untreated garbage• Animal wastes, organic wastes, leaves• Construction sediments and traffic emissions.• Zinc from weathering of aging pipes and gutters• Copper from brake linings, worn pipings• Used motor oil• Fertilizers

Industrial wastes in water• Food processing industries produce organic wastes that are readily

decomposed but have a high BOD.• Paper and paper mills produce waste that have high BOD and also toxic

compounds and sludge. The paper industries have however begun using methods of production of paper without the use of chlorine as a bleaching agent and that produce less toxic effluent.

• The electronics industry uses special techniques such as ion exchange and electrolytic recovery method to reclaim the toxic metal such as copper, lead and manganese.

Water Quality: DO

You can make a difference

Read preventing water pollution in page number 519Case in Point : Green Chemistry

Groundwater pollution

• Roughly half of the United States obtain the drinking water from groundwater, which is also withdrawn for irrigation and industry.

• The most common pollutants of groundwater such as pesticides, fertilizers, organic compounds seep into groundwater from municipal sanitary landfills, underground storage tanks, backyards, golf courses, and intensively cultivated lands.

• Underground petroleum storage tanks may be leaking at service stations in the United States.

Groundwater Pollution

Once groundwater is contaminated, it does not readily cleanse itself by natural processes. Methyl tertiary butyl ether, a gasoline additive is a common groundwater pollutant it is caused mainly from leaking underground gas-storage tanks.

Lake Maracaibo, Venezuela

It is the largest lake in South America. It receives water from several rivers, and water flows from it into the Caribbean Sea.This lake suffers from the effects of oil pollution and human wastes as well as contamination from farms and factories.Until recently raw sewage from the city was discharged directly into it, contributing to the nutrient overload.Modern sewage-treatment facilities were installed during the 1990s to take care of human wastes, but other problems need to beAddressed.

Po River, Italy

The Po River, which flows across northern Italy, empties into the Adriatic Sea.Source of pollution•Many cities including Milan, dump their treated and untreated sewage into the Po.•Industrial waste•Agricultural wastes.•Soil erosion and sediment deposition•Po is the source of drinking water•Po has jeopardized tourism and fishing in the Adriatic Sea.•It has closed swimming in some places.

Ganges River, India

• http://www.youtube.com/watch?v=wb_yDBmRgmU

• Watch this video to know how the holy river Ganges has been polluted over the years.

Ganges River, IndiaUsed for bathing and washing clothingSewage and industrial waste discharged into riverGanga Action Plan initiated by government

Construction of 29 sewage treatment plants

Kwale, KenyaMany Africans have serious health problems from drinking surface water contaminated with disease-causing organisms.Cholera and serious diarrhea outbreaks very common.Installation of village wells with hand pumps to provide clean drinking water (ground water).Acute drought lowered water levels in the early 2000s, drying up many wells.

Arsenic poisoning in BangladeshNaturally occurring in the ground water.

Improving Water Quality-Purification of Drinking Water

• In US most municipal water supplies are treated

• Collected from water or reservoir

• Treated

• Treated water distributed to customers

• Sewer lines bring sewage to treatment plant

• Sewage treated at sewage treatment plant

• Turbid water is treated with aluminum sulfate a chemical coagulant that causes the suspended particles to settle down.

• Then filtered through sand to remove remaining suspended particles.

• Then disinfected by adding chlorine.

Improving Water Quality-Purification of Drinking Water

Purification of Drinking Water

• Chlorine Dilemma– Chlorine kills disease causing organisms– Chlorine byproducts are linked to numerous

cancers, miscarriages and birth defects– Peru stopped using chlorine• 1991- huge cholera epidemic that infected 300,000

people and at least 3500 died since resumed

• Fluoridation– Prevents tooth decay– Linked to cancer, kidney disease

Purification of drinking water

• One alternative to chlorination is to use chloramine, a disinfectant produced by combining chlorine with ammonia. It does not form potentially harmful by products, it may cause lead level in drinking water system.

• Another way is to filter water through activated carbon granules.

• Fluoridation.

Municipal Sewage Treatment

Treatment of Human Waste

• Primary treatment: taking out solids– grating (removes debris)– moving screen (takes out smaller pieces)– grit tank (sand and gravel settle)– primary sedimentation tank (sludge settles)

Secondary treatment: biological degradation

– aeration tank (or filter bed, sewage lagoon)– fluid is mixed with a bacteria rich slurry– air is pumped in which promotes bacterial growth– bacteria and sludge is removed off the bottom (some is

returned to inoculate the aeration tanks)– water is sometimes chlorinated to kill bacteria, then

released

Tertiary Treatment: removal of plant nutrients

– removal of nitrates, phosphates and other nutrients which can cause algal blooms

– this can be accomplished by passage through a wetland or lagoon

• Sewage treatment works well except:– water in storm drains gets no treatment– during storms, raw sewage is dumped– treated water still has environmental effects

Municipal Sewage Treatment

Septic Tanks

A house-by-house alternative to sewer systemsWater is pumped into a tank

oils rise to top, solids to bottommiddle water is pumped into a series of pipes where it can evaporate and be worked on by bacteria

Works well if maintained, but can leak into ground water

Individual Septic System-Drain Field

Septic Tank and Field

Combined sewer system

• It is one in which human and industrial wastes are mixed.

• Is it good to have this practice or not? Explain• (Refer to Page number 519)• Read the article Preventing water pollution

and how you can make a difference and discuss with your partner as to whether you are practicing or plan to practice.

Laws Controlling Water Pollution

• Citizen Watchdogs to Monitor Pollution• Safe Drinking Water Act (1974)– Set uniform federal standards for drinking water– Maximum contaminant level

• Clean Water Act (1972)– EPA sets up and monitors National Emissions

Limitations– Effectively improved water quality from point

sources

Laws that Protect Groundwater

• Safe Drinking Water Act• Resource, Conservation and Recovery Act

Case-In-Point Green Chemistry