Wastewater consists of all of the water used in the home that goes down the drain and into the sewage collection systems, including water from showers, storm drains, sinks, dishwashers, washing machines and toilets. Some small businesses operate private wastewater treatment systems. Wastewater treatment plants operate 24 hours a day, seven days a week and help to stave off excessive pollution in the environment.
Primary and Secondary Treatment
Influent wastewater flows into a treatment plant, and effluent water flows out. There are two phases of general wastewater treatment, primary and secondary. The primary treatment phase involves screening the water to remove large objects such as sticks, stones and other things that could plug lines or block tanks. The secondary treatment phase uses biological treatment processes to clean the water.
Biological Treatment Processes
The first option used to turn unsettled solids to settled solids includes activation of the sludge by aeration and agitation, which allow the solids to settle. Bacteria are recycled through the aeration basin to increase and stimulate organic decomposition. Comparatively, we do the same thing to our laundry when we add detergent to clean it.
A second process is to use what is called trickling filters. This process is governed by the Clean Water Act. Beds of coarse media made of stones or plastic are laid up to 10 feet deep, and then the wastewater is sprayed into the air to allow it to trickle through. Microorganisms then break down the organic material. The filters drain at the bottom, and the wastewater is collected to undergo sedimentation.
The third process is called lagooning. This process is somewhat inefficient but can be used to some degree for wastewater treatment. This process uses sunlight, algae, microorganisms and oxygen to work. Some of this sludge is intended for beneficial use. When that is the case, it is called biosolids, and it must meet certain government-specified criteria depending on what it will be used for (fertilizer or soil enhancement).
Post Treatment Processes
Municipal wastewater is usually disinfected with chlorine after treatment. Other additives and agents used are ozone or ultraviolet light. This "third treatment" process, which takes place after the primary and secondary layers, is comparable to adding bleach to our laundry for disinfecting. It can also remove nutrients and absorb carbon for chemical removal of settled solids (sludge). The primary idea behind wastewater treatment is to cut down on pollution so that the water can be released back into the environment.
Water Shortages
Because of water shortages, treated wastewater pumped directly from sewage treatment plants is allowed to be used in some special cases where it won't be consumed. The main purpose of using reclaimed water is to conserve higher quality water for drinking.
Private Treatment Facilities
Private wastewater facilities use a variety of treatment options to dissolve contaminants before releasing them into municipal water supplies. More advanced technologies are used to get rid of contaminants, including oils, metals and solids. These technologies include the use of processes such as oil-water separation, activated carbon filters, dealkalization, dechlorination, demineralization, greensand filtration and reverse osmosis to clean water of bacterial contamination, dyes and grease, among other pollutants.
Tags: This process, Treatment Processes, primary secondary, settled solids, treatment phase