Biodegradable pollutants alone are not responsible for water pollution, though these indicate the level of pollution (through BOD values). Besides these, substantial pollution increases through non degradable or slow-degrading pollutants, such as heavy metals, mineral oils, biocides, plastic materials etc., that are dumped into the water. Also, we need to take some responsible steps to control of water pollution.
For biodegradable pollutants, we can control the pollution with their treatment for reuse and recycling. We need to remove the non-degradable toxic substances from water by suitable methods. In addition to these methods, we need to remember government Acts like some standards, conditions and requirements.
Simple Techniques to Control of Water Pollution
The various ways/techniques suggested for control of water pollution follows:
1. Stabilisation of the Ecosystem
This is the most scientific way to control water pollution. The basic principles involved are reducing waste input control, harvesting and removing biomass, trapping of nutrients, fish management and aeration. There are some methods used(biological and physical) to restore species diversity and ecological balance in the water body to prevent pollution.
2. Reutilisation and Recycling of Waste
Various kinds of wastes, including industrial effluents (such as paper pulp or other industrial chemicals), sewage/sullage of municipal and other systems, and thermal pollutants (waste water etc.), may be recycled for beneficial use. For instance, urban waste (sewage/sewage) can recycle to generate cheaper fuel, gas and electricity.
In Okhla, New Delhi, one large treatment plant for sewage recycling is already in operation. One distillery in Gujarat can treat 4,50,000 litres of water daily and generate energy equal to that produced by 10 tons of coal. NEERI is involved in developing suitable technology for wastewater reclamation through aqua-culture. Also, it utilises domestic and industrial wastewater in agriculture and detoxifying phenol and cyanides in waste by biological means.
3. Removal of Pollutants
Use the appropriate methods to remove various pollutants (radioactive, chemical, biological) present in the water body with absorption, electrodialysis, ion change, reverse-osmosis etc. Reverse osmosis is based on removing salts and other substances by forcing the water through a semipermeable membrane under pressure exceeding the osmotic pressure.
Due to this, flow occurs in the reverse direction. We use a power membrane that attracts the solvent and repulses the solute. Reverse osmosis uses to desalinate brackish water and can also be used for purifying water from sewage.
Council of Scientific and Industrial Research (CSIR), New Delhi, could devise the following techniques for the successful removal of pollutants from water:
A weak acidic cation exchange developed, which removes NH in the form of ammonium sulphate. This can be used for fertilisers. This can separate from the wastewater of industry by ion exchange technique.
This could be removed from chlor-alkali effluent plans using mercury-selective ion exchange resin. Paper mills, carbonisation plans, petroleum refineries, tanneries.
These could be removed from the wastewater of pulp resin plants by using polymeric absorbents.
(iv) Decolonisation of Water
An electrolyte decomposition technique could decolonise the wastewater from printing and sari dying industries.
(v) Sodium Salts
We need to remove this by the reverse osmosis method. Sodium sulphate from a rayon mill effluent could be easily removed. The water for reuse could also be recovered by this method. This method may recover 80% of protein and 80% of lactose from cheese.
Recently, researchers of some American laboratories (reported by the Wall Street Journal) have claimed to use solar power for cleaning up polluted waters cheaply. Experiments showed that a combination of sunlight and a catalyst such as titanium dioxide could break down the chemical toxicants of water. Such photocatalytic reactions can destroy pesticides, explosives, solvents, PCBs, dioxins and cyanides.