Improved monitoring and automation can deliver more efficient waste treatment and reduced energy consumption and improved effluent quality. The cost of treatment and the quality of effluent discharge can thus be significantly reduced.
Federal and State regulatory agencies are increasingly requiring additional water quality testing and controls of the toxicity of discharges to receiving streams. Granular Activated Carbon (GAC) helps meet these pollution regulations. If organic chemicals have been identified as contributing to discharge toxicity, Calgon Carbon Corporation can work with facilities, and their engineering firms, to help meet stringent criteria associated with their NPDES permit. GAC can be employed as a cost-effective treatment for removal of organic compounds and toxicity. Even in situations where activated sludge treatment or powdered activated carbon is used for primary wastewater treatment, post treatment with GAC may be necessary to achieve toxicity compliance.
If industrial wastewater entering a treatment works contains toxic components the rate of biodegradation will be inhibited or stop completely. This can result in failed consents and will certainly give rise to operational problems. Visible indications include deflocculation, bulking and the appearance of filamentous bacteria. Sometimes, there are no visible effects. When the sludge bacteria are inhibited, there is the possibility of toxicity carryover in the effluent that is discharged to receiving waters. With new environmental legislation being introduced, worldwide, to protect the natural environment, toxin discharge is now a serious concern for treatment plant managers.
In industrial manufacturing companies, before a new process comes on-line, it is important to measure the toxicity of the effluent stream. This is especially the case for companies who treat their own waste. From the toxicity value (EC50) obtained, it may be a cost-effective solution to simply discharge the effluent to the treatment works at a slow and defined rate to minimise damage to the activated sludge. Following a period of acclimatisation it is often possible to increase feed rates to the plant and this can again be managed using the Strathtox Respirometer. An alternative approach is to undertake toxicity reduction procedures, such as neutralisation or acid hydrolysis, in pilot-scale laboratory studies. The Respiration or the Nitrification Inhibition Test may be used for this. In the future, toxicity reduction may be stipulated by local authority, water company or publicly-owned treatment works prior to giving discharge consents. Toxicity reduction may be evaluated using toxicity tests on activated sludge provided by the treatment works.
Water companies, water authorities or publicly-owned treatment works (POTW) need to have some knowledge of the composition of the wastes they it receive. In addition to testing for ammonia and BOD or COD levels, treatment works can license industrial discharges on the basis of concentrations of some of the known toxic compounds. However, it is recognised that very many non-regulated toxic materials still enter the treatment works and reduce the efficiency of biodegradation, and may cause toxic shock. The way is now open for more widespread use of direct toxicity tests as a basis for toxicity-based consents. Samples of the industrial effluent are collected at source, for testing on the actual bacteria of the receiving activated sludge. The tests used are the Respiration Inhibition Test and the Nitrification Inhibition Test. Note that this approach mirrors that of the regulators of discharges to receiving waters, who are now using direct toxicity tests (DTA) or whole effluent toxicity tests (WET tests) in order to protect the receiving environment.