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Sewage Treatment Plants
Sewage treatment plants are designed and operated to remove contaminants from the in-fluent waste water. These plants can be used for both industrial waste water treatment and municipal waste water treatment. Proper treatment of sewage is critical to protect the public health and the environment.
Sophisticated equipment and controls are needed to ensure removal of pollutants to meet regulatory requirements. In addition, waste water treatment plant operators must have specialized training and experience to ensure the equipment is properly used to provide a clean effluent or reclaimed water.
Sewage Treatment Plant Design
Design of a waste water treatment plant depends upon the type of waste being treated and the quality of the receiving stream, river, lake or sea. Whenever possible, treated effluent from the sewage treatment plant should be reused for beneficial purposes like irrigation and industrial use. Regulatory agencies require various levels of sewage treatment based on the quality of the receiving water or type of reuse.
There are three basic waste water treatment levels. Primary treatment removes inorganic settle-able and floating solids. Secondary biological treatment provides removal of components like biochemical oxygen demand (BOD/COD/TOC) and suspended solids. Tertiary waste water treatment provides additional removal of nutrients such as nitrogen and phosphorus.
Engineers can use or combine numerous sewage treatment processes and technologies to provide the best results, depending on the in-fluent waste water characteristics and the effluent treatment requirements. These processes may include membrane bio-reactors, various activated sludge processes, filtration, and various disinfection methods among others.
The engineer must work closely with both the client and the regulatory agencies to determine the best waste water treatmeaant design. In addition, the engineers consider life-cycle costs of the equipment to keep operating costs as low as possible.
Sewage Treatment Plant Construction
Construction of the waste water treatment plant requires a high level of expertise on the part of both the engineer and the contractor. The contractor must work closely with the design engineer to properly interpret the sewage treatment plant construction drawings.
Retrofitting or upgrading an existing waste water treatment plant is even more difficult. Coordination between treatment plant operators, contractors, engineers and regulators is critical to keep the existing plant in compliance while building the new facilities.