More than half of most living organisms are made up of water alone. About seventy percent of Earth itself is covered in water. In fact, in extreme environments, humans can only survive without water for three to four days.
As important as water is for us all, waste and pollutants such as nitrogen oxides, sulfur dioxides, disease, sewage and more is constantly contaminating it. Because of these detrimental impacts on precious water resources, waste water treatment is a huge part of keeping our water clean. There are many ways wastewater can be treated. Many times water needs to go through more than one treatment before it is ready to go back into the environment. Here are just six different waste water treatment techniques being implemented today:
Wastewater treatment falls under processes of a physical, chemical, or biological nature. Waste water undergoes different levels or degrees of treatment as well: preliminary, primary, secondary, disinfection, sludge, and tertiary. Typically the processes and levels are combined during wastewater treatment.
1. Preliminary treatment
This is typically the first level of treatment used for cleaning wastewater at plants. The purpose of preliminary treatment is to ensure coarse materials are removed from raw wastewater in order to protect and maintain the equipment and subsequent treatment units. Screening, comminuting devices such as grinders, cutters, or shredders, grit chambers and pre-aeration tanks are commonly used devices during preliminary treatment.
2. Primary Treatment
About 60% of organic and inorganic sediments and floating materials, as well as incoming biochemical oxygen demand, suspended solids, and oils and grease are removed during primary waste water treatment. If preliminary treatment is not implemented, primary treatment becomes the first process in cleaning waste water. Some physical devices used during primary treatment include settling tanks, clarifiers or sedimentation tanks. Although sedimentation, a gravity separating technique, is one the more popular methods used in waste water treatment, advances in flotation methods are introducing more cost efficient, sustainable, and environmentally friendly waste water primary treatments. These new technologies are eliminating the need for a preliminary stage during treatment all together.
3. Secondary Treatment
Biological processes come into play during secondary treatment. Dissolved or suspended organic matter or dissolved organic biodegradable material (BOD) is biochemically decomposed in processes including trickling filters with secondary settling tanks, activated sludge and modifications with final settling tanks, intermittent sand filters, and stabilization ponds. These organic materials are essentially consumed by microbes that in turn convert them into carbon dioxide, water, and energy. Approximately 85% of suspended solids are removed at this point of Water Waste Treatment.
This type of treatment is implemented in order to make certain water is free or nearly free from pathogenic organisms as well as for odor control, the protection of plant structures and the reduction of biochemical oxygen demand (BOD). Chlorine can be used as a disinfectant, however, because of its own toxicity on life forms, ozonation has started to pioneer its way into waste water treatment processes.
The waste that is separated from the water during waste water treatment is known as sludge. Even sludge needs to undergo some form of treatment to prepare it for ultimate disposal. Thickening, digestion with or without heat, drying on sand bed, conditioning with chemicals, elutriation, vacuum filtration, heat drying, incineration, wet oxidation, or centrifuging are many types of sludge treatment used. However, some are more cost effective and environmentally healthy than others.
6. Tertiary Treatment
Tertiary treatment comes after primary and secondary treatment as an additional means of treatment. Intermittent sand filters for increased removal of suspended solids is typically what tertiary treatment consists of. The additional filtration is said to be a more environmental friendly way of cleaning water as purely as possible because it does not typically use chemicals.
Chemical use such as chemical feed units, mixing devices or flocculators are a few units that may be employed throughout the waste water treatment process.
Contaminated water is more of an issue throughout the world than most people pay attention to. In the United States especially, it is easy to take for granted such a valuable resource such as water and waste water treatment processes and facilities. Even here, our water is not up to par for living organisms and aquatic ecosystems to survive and thrive. Although waste water treatment is behind the scenes, it is an irreplaceable resource in nearly every industry and aspect of our lives.