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Waste-water effluent treatment is vital to protect the health of the environment, the humans and animals in the region. When municipal waste-water enters a treatment facility and undergoes contaminant removal, the resulting product intended for discharge is known as effluent. It is critical that this effluent water be environmentally safe and fit for disposal. Why Is Effluent Treatment Necessary? Municipal waste-water contains reams of harmful bacteria, along with a mixture of fats, oils and grease that must be treated before coming into contact with the outside world to prevent the spread of disease and pollution. However, the degree of effluent treatment depends on the quality of the water in which it will be discharged. If the receiving water is upstream of a water supply, stricter standards apply. If the effluent will be quickly diluted in a large, coastal body of water, less treatment is needed. What Are the Main Goals of Effluent Treatment? Primarily, the goal of effluent treatment is disinfection. Through a number of treatment types, all potentially harmful microorganisms must be extracted from the effluent. First, chlorination breaks down residual organic materials. Another option includes ultraviolet (UV) light exposure. UV rays do not spread chemicals in the water, rather they work at breaking down the genetic structure of contained bacteria so they are unable to reproduce. Disinfection treatment may also involve producing ozone, which reacts with and oxidizes unwanted organic materials. The secondary goal of effluent treatment is odor control. Using carbon reactors, chlorine, hydrogen peroxide and other substances, the unpleasant gases are neutralized before effluent discharge takes place. What Are the Steps of Treatment? The inflowing waste-water goes through a pretreatment process in the beginning. All objects are caught in a filter, including branches, leaves and garbage that may have entered the waste-water flow. The waste-water also undergoes sand removal so the coarse grit does not damage the treatment equipment. In the primary treatment phase, the waste-water flows into a basin where the sewage sludge settles on the bottom, and the fats, oils and greases rise to the surface. The surface coating is skimmed off and the sludge at the bottom is collected and moved to a specific sludge treatment system. In the secondary treatment phase, filtration plays a key role. Using either fixed-film or suspended growth tactics, the waste-water undergoes physical, chemical and biological filtration to further extract unwanted suspended solids, heavy metals and other microorganisms. While the two types of secondary treatment tactics differ in their approach, the results are similar. Fixed-film systems, such as a trickling filter, involve the waste-water running through a layer of bio film which uses absorption and adsorption to remove microorganisms. Suspended growth systems, such as an activated sludge process, involves combining oxygen and biological floc with the primary treated waste-water. The organic compounds are then filtered out and removed for sludge treatment. Tertiary treatment is the final step in “polishing” the effluent before it enters the environment. This includes sand filtration to fully remove all lingering organic matter. Secondly, nitrification and denitrification may be necessary to transform high levels of nitrogen into a gas that will evaporate from the water supply. Also, phosphorous must be removed from the water as well by enhanced biological phosphorous removal. A buildup of nitrogen and phosphorous in discharged effluent can eventually contribute to an algae bloom. Contact a fluid systems specialist for a consultation regarding your specific waste-water effluent treatment needs.
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