sewage 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 ?
From the current capacity of three existing sewage treatment plants Swargashram, Lakkarghat and IDPL, approximately 23 MLD of sewage treatment capacity is available.
The Doha North Sewage Treatment Plant Project is worth approximately QR3.
Summing up, David Bradley said it appeared the sewage treatment works were "out of sight, out of mind".
In the UK, for phase three of Bellozanne Sewage Treatment, Doosan Enpure will build the plant to treat 71,000 tonnes of sewage per day, and complete it in 2020.
Wen Yibo, the chairman of Sound Global, commented that this project is another breakthrough for Sound Global in the township sewage treatment plant construction in Guangdong Province of China following the winning of the bid for the sewage treatment plant BOT project in Huazhou (Yangmei) Food Processing Base in Guangdong Province.
Stantec will continue monitoring groundwater wells at the Airport sewage treatment plant and analyzing to see if the plant's substantial completion will result in decreased contamination levels.
Quality assured Under the ordinance, which merely expounds on a provision of the Green Building Ordinance of 2009 pertaining to sewage treatment plants, existing markets in Quezon City are told to get permits from the Environmental Protection and Waste Management Department (EPWMD), Market Development and Administration Department (MDAD) and the city building official (CBO).
Municipal Corporation cannot deny of sewage treatment.
The smell has reduced almost 90 per cent in the last three years, and [the residents] might have psychological effects from living so close to the sewage treatment plant," he said.
Summary: Dubai Municipality announces task force to find ways to contain, control and minimise the odour emissions from the Dubai based Al Aweet Sewage Treatment Plant
We have also started testing at the Jeddah airport sewage treatment plant a year ahead of schedule.
KARACHI, May 17 -- Work on the proposed greater sewage treatment plant for the city, a project that has remained in limbo for three years as the federal government had refused to take up the project, might start in three months, Daily Times has learnt.