Waste Water Treatment – Releasing untreated water, which is effluents from sewage, industrial or agricultural use can cause pollution of ground or surface water and pose serious health hazards to humans if such water is used directly or indirectly. Therefore, treatment of such effluents is critically important for removing or minimizing contamination level so that the water can be safely re-used or disposed off without risk to health, local ecology or environment, in general. Water recycling can also help to save costs and resources in long run and in several cases; by-products can be used as fertilizers.
Wastewater treatment from different industries has different types of contaminants. It varies from particulate organic matter, dissolved salts, chemicals, acids, detergents, solvents, oils etc. Therefore, different combination of methods and strategies are used for efficient and effective treatment of waste water from different industries in water treatment plants. With optimal strategies and plant designs, waste water from different sources can be treated effectively.
The industrial wastewater treatment is designed such that water treatment can be done through several processes – from treating the water for unwanted salt ions (contributing to brine) to oils to alkalies and acids to removal of toxic substances from the water. Depending of types of salt ions the removal (brine treatment) is facilitated using specific processes such as evaporation, membrane filtration, ion exchange processes etc. and thus also need specific equipment and know-how. This step helps in reducing volume of discharge and recovery of reusable salts for economical purposes.
Presence of solid particles may pose challenge in further water treatment. Therefore, depending on necessity, sedimentation, ultra-filtration and flocculation are used to remove solid particles successfully. Skimming is used as a cost-effective method to remove floating oils from effluents. Further, standard oil-water separators, which use gravity separation, are used to remove suspended solids and oil remnants from water.
Presence of synthetic organics such as pharmaceuticals, pesticides, paints etc. in water can pose grievous harm, if such water is released untreated. Choice of method in such case is of utmost importance. Methods such as distillation, advanced oxidation processing are used for effective removal of synthetic organic content in waste water effluents. The acids and alkalies are neutralized in controlled conditions and the precipitate thus formed is treated using solid waste treatment.
The biodegradable organic material can be commonly present in sewage, industrial and agricultural waste water. Therefore, similar methods of wastewater treatment facilities can be used in waste water treatment plants for treating water effluents for presence of such material. Biochemical processes such as activated sludge method or microbial aided filtration process such as trickling filter processes are useful for such treatments. The treatment plants are designed as per needs and types of processes used.
Primarily four types of treatment plants are used for activated sludge process wherein air and microbes are used to oxidize the biodegradable content in an aeration tank to produce sludge. Such waste sludge is allowed to settle in a settling tank so that it can be removed for any necessary further treatment. Different types of activate sludge wastewater treatment facilities are built based on factors such as expected volumes of waste water to be treated, available land etc.
Package plants are built and used when the volumes may not be so high and maintenance support is minimal. Only the aeration part is focused on in such plants and settlement part is not included. Thus, the biological activated and aerated sludge (flocks) produced is available for reuse in the aeration tanks for processing incoming waste water. The most advantageous benefit is the safe end products, water and carbon dioxide produced from this treatment, which are discharge back in to the environment.
Trickling filter plants are time tested and well characterized. They use absorption and adsorption of organic content of water to microbial film / layer as the effluent flows downwards over gravel, moss or plastic surface under aerated conditions.