Wastewater is any water that has been adversely affected in quality by human activities. Wastewater can originate from a combination of domestic, industrial and agricultural activities, as well as storm water from surface run-off. The contamination of bodies of water such as lakes, rivers, oceans, aquifer and ground water by wastewater pollutants has led to the degradation of water quality harmful to the lives of humans, animals and plants in many noticeable ways. Now-a-days use of wastewater for a variety of purposes is gaining increased popularity as a means of preserving scarce freshwater resources.
The two basic types of wastewater treatment are (A) Conventional treatment (B) Treatment by natural systems.
Conventional Wastewater Treatment is basically concerned with removal of suspended & floatable materials, treatment of biodegradable organic, removal of toxicant & elimination of pathogenic organisms so that the quality of discharge water is improved to reach permissible levels for discharge in to water bodies and/or agricultural purposes. Broadly the steps involved in the treatment of wastewater.
Preliminary Treatment for removal of debris, gross solids, grit, oil & grease by passing wastewater through screens, grit chambers & skimming tanks
Primary Treatment tanks are generally circular or rectangular in shape. The purpose is to reduce the velocity of the incoming wastewater stream thereby allowing the stable solids to fall to the bottom of the tank. Typically 50-60% of the suspended solids are removed in primary settling tanks. In addition, BOS is reduced by 20-50% and the bacterial count by 25-75%.The pH is generally unaffected by primary settlement.
Secondary Activate Sludge (Suspended Growth)Treatment involves the production of an activated mass of micro-organism capable of aerobically stabilizing the organic content of waste. Wastewater is introduced into an aerated tank of micro-organism collectively referred as activated sludge(floc) with the combination is maintained in suspension by surface mechanical or submerged diffused aeration. The floc is suspension of millions of aerobic micro-organisms consisting of bacteria, fungi, yeast, protozoa, etc. To operate this process on a continuous basis the floc must be separated in a secondary (clarifier) settlement tank and partly returned to the aeration tank. Secondary activated treatment removes 8096 COD, 85-90%BOD, 30% P 50%
Tertiary Treatment is the final treatment for removal of fine suspended solids, traces of organic and bacteria by adsorption by activated charcoal, ion exchange, ultra-filtration followed by disinfection by UV/Electro-chlorination/Chlori nation to kill/inactivate pathogenic bacteria prior to the treated effluent discharge.
Treatment by Natural Systemic usage of natural eco-systems for wastewater treatment that have been used for centuries. Natural treatment systems are artificially built treatment eco-systems such as constructed wetlands, soil filters, stabilization ponds, etc occurring in natural habitats but done in a more controlled manner. Attention has been drawn to these natural treatment systems because of lower capital cost as well as lower maintenance & operation costs. In the case of natural treatment methods it is necessary to pay special attention to the process of pre-treatment for removal of suspended solids. The natural treatment methods rely mainly on natural characteristics of the wastewater with relatively simple technological implementation with low energy consumption and at a low investment cost as well as operation & maintenance cost in comparison to conventional treatment. Water as an asset class is bound to become eventually the single most important physical commodity dwarfing oil, copper, agricultural products and precious metals. Let’s strive to protect it. – Mr. Sripathy Krishnabharathi Sakthivale
