sewage treatment

(redirected from Secondary Treatment)
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sewage treatment:

see septic tankseptic tank,
underground sedimentation tank in which sewage is retained for a short period while it is decomposed and purified by bacterial action. The organic matter in the sewage settles to the bottom of the tank, a film forms excluding atmospheric oxygen, and anaerobic
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; seweragesewerage,
system for the removal and disposal of chiefly liquid wastes and of rainwater, which are collectively called sewage. The average person in the industrialized world produces between 60 and 140 gallons of sewage per day.
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sewage treatment

[′sü·ij ‚trēt·mənt]
(civil engineering)
A process for the purification of mixtures of human and other domestic wastes; the process can be aerobic or anaerobic.

Sewage treatment

Unit processes used to separate, modify, remove, and destroy objectionable, hazardous, and pathogenic substances carried by wastewater in solution or suspension in order to render the water fit and safe for intended uses. Treatment removes unwanted constituents without affecting or altering the water molecules themselves, so that wastewater containing contaminants can be converted to safe drinking water. Stringent water quality and effluent standards have been developed that require reduction of suspended solids (turbidity), biochemical oxygen demand (related to degradable organics), and coliform organisms (indicators of fecal pollution); control of pH as well as the concentration of certain organic chemicals and heavy metals; and use of bioassays to guarantee safety of treated discharges to the environment.

In all cases, the impurities, contaminants, and solids removed from all wastewater treatment processes must ultimately be collected, handled, and disposed of safely, without damage to humans or the environment.

Treatment processes are chosen on the basis of composition, characteristics, and concentration of materials present in solution or suspension. The processes are classified as pretreatment, preliminary, primary, secondary, or tertiary treatment, depending on type, sequence, and method of removal of the harmful and unacceptable constituents. Pretreatment processes equalize flows and loadings, and precondition wastewaters to neutralize or remove toxics and industrial wastes that could adversely affect sewers or inhibit operations of publicly owned treatment works. Preliminary treatment processes protect plant mechanical equipment; remove extraneous matter such as grit, trash, and debris; reduce odors; and render incoming sewage more amenable to subsequent treatment and handling. Primary treatment employs mechanical and physical unit processes to separate and remove floatables and suspended solids and to prepare wastewater for biological treatment. Secondary treatment utilizes aerobic microorganisms in biological reactors to feed on dissolved and colloidal organic matter. As these microorganisms reduce biochemical oxygen demand and turbidity (suspended solids), they grow, multiply, and form an organic floc, which must be captured and removed in final settling tanks. Tertiary treatment, or advanced treatment, removes specific residual substances, trace organic materials, nutrients, and other constituents that are not removed by biological processes. Most advanced wastewater treatment systems include denitrification and ammonia stripping, carbon adsorption of trace organics, and chemical precipitation. Evaporation, distillation, electrodialysis, ultrafiltration, reverse osmosis, freeze drying, freeze-thaw, floatation, and land application, with particular emphasis on the increased use of natural and constructed wetlands, are being studied and utilized as methods for advanced wastewater treatment to improve the quality of the treated discharge to reduce unwanted effects on the receiving environment. See Absorption, Sewage, Sewage disposal

On-site sewage treatment for individual homes or small institutions uses septic tanks, which provide separation of solids in a closed, buried unit. Effluent is discharged to subsurface absorption systems. See Septic tank, Unit processes, Water treatment

sewage treatment

Any artificial process to which sewage is subjected in order to remove or alter its objectionable constituents and to render it less dangerous from the standpoint of public health.
References in periodicals archive ?
The demographic characteristics, related symptoms, and the results of primary and secondary treatment of the patients were evaluated.
Xylem will supply highly efficient and reliable treatment technologies for use during secondary treatment at the plant, including the company's Sanitaire fine bubble aeration technologies, Flygt ultra low-head pumps and low-speed mixers, aeration blowers, stainless steel air mains and Flygt Jet aerators in the aerobic digesters, said the statement.
"In conjunction with Kharafi National, the project contractor, our optimized solution during secondary treatment will help create an efficient and effective system that will deliver clean reusable water to this arid, water-challenged region."
* $52.4 billion to meet secondary treatment standards.
AV Terrace Bay runs a pulp mill converting wood into pulp using a kraft pulping process, which generates industrial effluent that undergoes primary and secondary treatment prior to being discharged into Lake Superior via Blackbird Creek.
Under EU rules, by 2000 Ireland should have had secondary treatment of sewage in place for towns and cities with populations of more than 15,000.
Request of offers from first class Egyptian contractors with experience in the operation & maintenance of waste water treatment plants in cooperation with international contractors having the same background requesting them to submit technical and financial offers to operate and maintain El Gabal El Asfar water treatment plant (Stage 1) re contract 16 involving the secondary treatment - including sludge treatment - with an average capacity of 1.1 million M3/ day in addition to optimizing the use of (further) 300,000 M3/ day based on annual bases and renewable for five equal periods with same conditions.
'Municipal wastewater discharged to the Pacific Ocean requires considerable energy for secondary treatment (biological oxidation and assimilation of organic matter) and pumping through a long ocean outfall.
The project is part of the company's environmental strategic plan which will provide secondary treatment to the refinery's waste water to meet the discharge limits set by Bahrain's Supreme Council for
Moreover, waste water that penetrates collection systems should be subjected to secondary treatment before being discarded.
If that's the case, why not take the step to provide secondary treatment? Steckel says secondary treatment typically requires removal rates of 85/85, or 85 percent of the biochemical oxygen demand and 85 percent of the solids.
All had maintained or improved previous results, although compliance rates remained below 30 % in Bulgaria, Cyprus, Estonia, Latvia and Slovenia.Compliance rates for secondary treatment are 82 %, up four points since the previous report.