I must wonder how the ...

I must wonder how the percentage of pollution is being measured. If it is in biochemical oxygen demand, then it may appear as if the industries are contributing only 25% because many industrial effluents contain pollutants that inhibit the effective natural removal systems and microbial activity and/or oxygen which must be supported. Industrial discharges may contain heavy metals and volatile organics which cannot be measured by the BOD test because they cannot be readily broken down by the microorganisms. Non-point sorce pollution from runoff and inappropriate domestic contributions to the water body do contribute significant pollutant loadings which add nutrients resulting in excess algae and potentially very serious drops in dissolved oxygen! However, the point source contributions of industrial discharges, particularly if not pretreated prior to discharge, can hamper all natural systems in the river basin from the ability to purify the water and also cripple the ability of an installed and properly operating sewage treatment system! The industrial discharges must be within a certain pH range and temperature. They must not contribute inappropriate loadings of BOD to the river. They must contain very low amounts of the priority pollutants. Testing of industrial effluent must involve flow measurement, metals analysis and organic analysis using gas chromatography and mass spectroscopy. The publication Standard Methods for the Examination of Water and Wastewater lists the pollutants and their analytical methods. Standard Operating Procedures are available and I have drawn up many myself. The two places to limit pollutants are the industries and the runnoff. I cannot stress the importance of industrial discharge pretreatment enough. The Code of Federal Regulations published by the US government (CFR Part 403) lists industries by category and also lists limits for the parameters typically discharged by each type of industry. HOWEVER, these limits are too lenient and local limits must be determined by experimentation and analysis because a receiving body of water cannot handle loadings of this level if several industries are discharging to the same water body or the same wastewater treatment facility. It is usually hard to look at the industrial piece of this puzzle because of potential costs and loss of revenue, but this is not acceptable is pollution is to be controlled. I have seen electroplaters turn around from killing entire wastewater treatment facilities to reclaiming nearly all of the copper in their effluent, and turning it into pure copper sheets to be reclaimed by the industrial sector. Industries may not comply with pollution control efforts if it is cost effective for them to continue to pollute, so they may need to be charged for the pollutants they discharge and be published as significant water polluters. The government must make the conscious decision to choose water quality over industrial privilege. Once polluting is unpopular or costly it will be the beginning of success and reduction in waste of usable resources and the ability of the water body to recover. All sanitary sewage must go through an effectively operating wastewater treatment facility. Temporary package plants can be helpful, but are not a permanent or cost effective solution for high population areas, but some form of treatment is necessary to reduce the pathogens and the risk of waterborne disease. Best wishes for success in this important project!