Wastewater treatment is a process that removes contaminants from sewage and creates an effluent suitable for discharge. Wastewater treatment is a vital step to prevent the pollution of water by the discharge of raw sewage. There are many different types of wastewater treatment plants. This article will discuss some of the main types and how they work.
Secondary treatment
Secondary treatment at a wastewater treatment plant is an important part of the treatment process. It uses biological processes to reduce dissolved organic and solid pollution. This process also reduces the pathogenic organism count in the influent stream. This treatment also reduces the sludge transport and disposal costs.
Wastewater treatment plants have different types, depending on how they process wastewater. Solid wastes are passed through screens to remove bulky suspended solids in some types. In other types, wastewater is directed to a digester and subjected to anaerobic digestion. This process creates methane gases and nutrient-rich bio-solids. These are then recycled or sold to local businesses. Some treatment plants also generate energy from methane gas. This gas can be used for power generation or to heat the digesters.
Depending on the circumstances, secondary treatment can be a success or a failed process. The process is most effective when the waste load is relatively low. If the wastewater treatment plant does not have enough waste, secondary treatment may not function properly, and the waste may not reach its disposal site. The wastewater may also be diluted due to the addition of large volumes of relatively uncontaminated water. This can be caused by stormwater runoff. Large swimming pools and cooling water discharges can also dilute the effluent.
Secondary treatment at a wastewater treatment plant uses a biological fixed-film process. The primary treatment process removes coarse and suspended solids, and the second process allows wastewater to interact with a biological film, removing pollutants. The water is then discharged into a body of water.
Surface skimmers
Skimming equipment removes the free-phase product layer from wastewater. The process eliminates the need for down-well equipment and reduces overall costs. This equipment can also salvage products for reuse, reducing overall costs. Several types of skimming equipment are available for wastewater treatment plants.
Surface skimmers are one of the most economical ways to remove scum from wastewater. This equipment typically features a mechanical blade that catches scum at the water's surface. They are typically mounted on a support truss, which directs scum to the weir gate. The operating time cycles of this equipment depend on the type of floatable material in the wastewater.
A typical surface scum skimmer comprises a horizontal scum trough 40 and an upper opening 42. The trough is typically made of pipe to ensure a cost-effective construction. Braces 50, usually fabricated from flat plates, separate the slots and provide structural rigidity.
Lagoons
Lagoons are a key component of the wastewater treatment process. The size and shape of a lagoon depend on the treatment process, climate, and other factors. The shape of a lagoon is usually designed to maximize water retention. This is the main goal for a treatment lagoon.
Over time, algae can build up in lagoons. Algae uses dissolved C02 for photosynthesis, which increases the acidity of water. The pH of lagoon water can reach as high as 10. Also, algae consume oxygen during respiration, releasing C02 into the water. During decay, dead algae cause foul odours. However, these problems can be avoided by ensuring proper lagoon operation.
Operators of wastewater treatment plants should monitor the water levels in the lagoons at regular intervals. This helps them make decisions and take action when the levels are too high. It is also important to measure the percentage of solids and volatile solids in the lagoons. They should also monitor air patterns in the lagoons and read the pressure gauges of air blowers. The results of these tests should be analyzed and displayed on trend charts.
Enhanced nutrient removal
Enhanced nutrient removal (ENR) at wastewater treatment plants is an important step in the treatment process. Conventional biological processes do not remove total nitrogen and phosphorus, and wastewater treatment facilities are required to reduce nutrient concentrations in the effluent to safe levels. To meet this goal, wastewater treatment facilities must make major process modifications. For example, they may need to make part of their aeration basins anaerobic in order to limit nitrification capacity.
The EPA has developed numerous educational materials on nutrient pollution and wastewater treatment. These resources include factsheets, reports, and educational websites. The EPA has also launched an information clearinghouse that will provide POTW operators with data on cost-effective and innovative wastewater technologies. The site includes maps and case studies.
Excessive nutrient discharges are a major source of environmental concerns. Regulatory agencies have set strict limits for point source and non-point source nutrient discharges. To meet these new environmental regulations, wastewater treatment facilities must undergo upgrades to remove these pollutants from water.
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