CSS Environmental Sciences Environmental Pollution and Control Syllabus

What are point and non-point sources of water pollution?

Point sources discharge from a single identifiable location (e.g. a factory pipe or sewage outfall); non-point sources are diffuse (e.g. agricultural runoff, urban storm runoff).

List the major categories of water pollutants.

Pathogens, oxygen-demanding wastes (organic matter), plant nutrients, toxic chemicals/heavy metals, sediments, thermal pollution, and radioactive substances.

What is thermal pollution of water and its main effect?

Discharge of heated water (often from power plant cooling) that raises water temperature, lowering dissolved oxygen and stressing or killing aquatic life.

What is eutrophication?

Nutrient enrichment of water bodies (mainly by nitrogen and phosphorus) that triggers excessive algal/plant growth, oxygen depletion, and degradation of the ecosystem.

Outline the sequence of events in cultural eutrophication.

Nutrient runoff (N, P) → algal bloom → algae die and decompose → bacterial decomposition consumes oxygen → dissolved oxygen drops (hypoxia) → fish kills and dead zones.

Which nutrient is usually the limiting factor for eutrophication in freshwater?

Phosphorus is typically the limiting nutrient in freshwater, whereas nitrogen often limits in marine/coastal systems.

What is BOD and what does a high BOD indicate?

Biochemical Oxygen Demand — the oxygen consumed by microorganisms to decompose organic matter over 5 days at 20°C. High BOD indicates heavy organic pollution and low water quality.

What is COD and how does it compare to BOD?

Chemical Oxygen Demand measures oxygen needed to chemically oxidize all organic matter (biodegradable and non-biodegradable). COD is always ≥ BOD and is measured faster (hours vs 5 days).

What does Dissolved Oxygen (DO) indicate about water quality?

DO is the amount of oxygen dissolved in water; high DO (>6 mg/L) indicates healthy water, while low DO indicates pollution and poor ability to support aquatic life.

What pH range is considered safe for drinking water under WHO/most standards?

A pH of approximately 6.5 to 8.5 is considered acceptable for drinking water.

What microbiological indicator is used to detect fecal contamination of water?

Total and fecal coliform bacteria, especially E. coli, used as indicator organisms; drinking water should contain zero coliforms per 100 mL.

Define TDS and its significance in water quality.

Total Dissolved Solids — the combined inorganic and organic substances dissolved in water (mg/L). WHO recommends <1000 mg/L for drinking; high TDS affects taste and indicates contamination.

What are turbidity and its main causes in water?

Turbidity is the cloudiness of water caused by suspended particles (silt, clay, microbes, organic matter); measured in NTU, with drinking water ideally below 5 NTU.

What are the three main stages of conventional wastewater treatment?

Primary (physical settling/screening), secondary (biological removal of organic matter), and tertiary/advanced (removal of nutrients, pathogens, dissolved solids).

What is achieved in primary wastewater treatment?

Physical removal of suspended solids and floating material by screening, grit removal, and sedimentation; removes ~30–40% of BOD and ~50–60% of suspended solids.

What happens during secondary (biological) wastewater treatment?

Microorganisms break down dissolved and suspended organic matter, typically via activated sludge or trickling filters, removing up to ~90% of BOD.

What is the activated sludge process?

A secondary treatment where wastewater is aerated with a microbial floc (activated sludge); microbes consume organic matter, then sludge is settled and partly recycled.

What is the purpose of tertiary wastewater treatment?

Advanced polishing to remove nutrients (N, P), residual solids, pathogens, and dissolved substances using filtration, chemical precipitation, and disinfection (e.g. chlorination, UV).

How is disinfection of treated wastewater commonly achieved?

By chlorination, ozonation, or ultraviolet (UV) radiation to kill remaining pathogenic microorganisms before discharge.

What are the major sources of soil pollution?

Industrial waste, agrochemicals (pesticides/fertilizers), heavy metals, improper solid waste disposal, sewage sludge, oil spills, and acid rain deposition.

How does soil pollution affect agriculture and health?

It reduces soil fertility and crop yield, accumulates toxins/heavy metals in crops (bioaccumulation), contaminates groundwater, and harms soil microorganisms and human health via the food chain.

What is biomagnification and give an example pollutant.

The increasing concentration of a persistent toxin at higher trophic levels of a food chain. Classic example: DDT, which magnifies up to top predators causing eggshell thinning in birds.

What is waterlogging and what causes it?

The rise of the groundwater table to the root zone or surface, saturating soil. Caused by over-irrigation, poor drainage, canal seepage, and lack of proper drainage systems.

How does waterlogging lead to soil salinity?

A high water table brings dissolved salts toward the surface; as water evaporates, salts are deposited in the root zone, causing salinization that harms crops.

What are the main effects of soil salinity on agriculture?

Reduced osmotic water uptake by plants, ion toxicity, poor germination, lower crop yields, and eventual abandonment of land — a major problem in Pakistan's Indus basin.

Name remedial measures for waterlogging and salinity in Pakistan.

Tile/surface drainage, tube wells (SCARP projects), lining of canals, controlled irrigation, gypsum application for sodic soils, and salt-tolerant crops.

What is deforestation and list its major causes.

The permanent removal/clearing of forests. Causes: agricultural expansion, logging for timber and fuelwood, urbanization, mining, road building, and overgrazing.

List the major environmental consequences of deforestation.

Soil erosion, loss of biodiversity, disrupted water cycle, increased atmospheric CO2 (global warming), flooding, landslides, and desertification.

What is desertification?

The degradation of land in arid, semi-arid, and dry sub-humid areas into desert-like conditions, caused by climate change and human activities such as overgrazing and deforestation.

Name the principal human causes of desertification.

Overgrazing, deforestation, over-cultivation, poor irrigation leading to salinization, and overexploitation of water resources, often combined with drought.