Strategies for Control of Environmental Pollution and Water Preservation

Controlling environmental pollution in practice combines engineering measures applied at the

source of emission with deliberate strategies to protect and conserve water resources.

Source-level control of air pollution includes: using cleaner or desulfurised fuels (low-sulfur

diesel, CNG, unleaded petrol) so that less $\text{SO}_2$, particulate matter and toxic lead compound

is generated in the first place; fitting catalytic converters to vehicle exhausts, which use a

catalyst to convert unburnt hydrocarbons, $\text{CO}$ and $\text{NO}_x$ into less harmful

$\text{CO}_2$, water and nitrogen before the exhaust gas leaves the tailpipe; and fitting industrial

stacks with electrostatic precipitators, bag filters or wet scrubbers (Section 13.6) to trap

particulate matter and acidic gases before they are released.

Source-level control of water pollution relies mainly on treating sewage and industrial

effluent before it is discharged -- removing suspended solids, breaking down biodegradable organic

matter (to lower its BOD), and neutralising or removing toxic substances -- so that the load

entering a river or lake is kept well within what the water body can absorb without becoming

polluted.

Water preservation and protection, distinct from pollution control but closely related to it,

covers practices aimed at conserving the quantity and quality of available water:

• Rainwater harvesting -- collecting and storing rainwater, or channelling it to recharge groundwater, rather than allowing it to run off and be lost, which both conserves a scarce resource and reduces pressure on other, already-stressed water sources.
• Effluent treatment before discharge -- ensuring that sewage and industrial wastewater are treated to remove pollutants and lower their BOD before they are released into any natural water body, rather than relying on the water body itself to dilute and absorb untreated waste.
• Watershed management -- managing land use across the whole catchment area that feeds a river or lake (controlling erosion, limiting deforestation, regulating construction near water bodies) so that sediment, fertiliser and pesticide runoff into the water system is minimised.
• Responsible fertiliser and pesticide use near water bodies -- applying only what crops …