Similar to air quality, water quality can be improved by two approaches:

• proactive (water pollution control) or
• reactive (treatment or remediation of polluted water).

Water pollution control

Potential water contaminants (as discussed under Water Pollution) are prevented from coming into contact with water. It is probably not very practical to achieve 100% isolation of water from the contaminants, but measures to limit the extent of pollution should be adopted. For instance, direct dumping of sewage, wastewater, industry processing waters and other chemicals into water bodies with the expectation that the wastes will be assimilated into the water environment should be stopped and has been stopped in several countries where it was previously practiced.

Leakages from tanks, pipelines, landfills, etc should be minimised with proper engineering and regulatory practices. Most governments now have guidelines for tanks (above ground or underground), pipelines and other infrastructures to prevent accidental discharges to land or water bodies. There are also transportation guidelines for offshore movement of petroleum products.

Water treatment or remediation

Notwithstanding the level of water pollution measures taken, we still have tremendous spills to water bodies, leaks of tanks and pipes, leachates to underground water aquifers from landfills and septic systems etc,.

Polluted water bodies are remediated using a combination of certain technologies and provisions of Government or local authority developed acts, regulations and guidelines.

The laws and guidelines specify acceptable concentrations of different contaminants in water meant for different purposes. For instance, the contaminant concentrations in drinking water will be much lower for the concentrations in water to be used for agricultural (e.g. irrigation) purposes and so on.

The technologies, on the other hand are used to reduce contamination of the water to the levels specified in the laws or guidelines. Examples of water remediation/purification technologies are:

• Conventional water treatment plants - having differing complexity based on the level of contamination of the water. Treatment processes include screening/straining, filtration, coagulation/flocculation, sedimentation, chlorination etc.
• In-situ groundwater treatment approaches;
• Ex-situ (out of site) groundwater treatment approaches (e.g. Pump and Treat method).

Usually, some similar approaches are used for the cleanup of soil and water. Consequently, the various approaches for remediation of water and soil are being developed under the title Site Remediation Technologies