Discharged from homes and businesses alike, sewage usually contains a mixture of human waste, food remnants, water used in washing machines, and any other items that may have found their way into the sewage system. Many municipalities operate wastewater treatment plants that help to purify the sewage and recycle the water for other uses, such as watering lawns. In many areas, sewage also includes liquid waste from industry and commerce. The separation and draining of household waste into Greywater and Blackwater is becoming more common in the developed world, with Greywater being permitted to be used for watering plants or recycled for flushing toilets.
Most sewage also includes some surface water from roofs or hard-standing areas and may include storm water runoff. Sewerage systems capable of handling storm water are known as combined systems or combined sewers. Such systems are usually avoided now since they complicate and thereby reduce the efficiency of sewage treatment plants owing to their seasonality. The wide variability in flow, affected by precipitation, also leads to a need to construct much larger, more expensive, treatment facilities than would otherwise be required.
In addition, heavy storms that contribute greater excess flow than the treatment plant can handle may overwhelm the sewage treatment system, causing a spill or overflow.
Modern sewer developments tend to be provided with separate storm drain systems for rainwater. As rainfall travels over roofs and the ground, it may pick up various contaminants including soil particles and other sediment, heavy metals, organic compounds, animal waste, and oil and grease. See urban runoff. Some jurisdictions require storm water to receive some level of treatment before being discharged directly into waterways.
Examples of treatment processes used for storm water include retention basins, wetlands, and buried vaults with various kinds of media filters, and vortex separators to remove coarse solids.
Sanitary sewers are typically much smaller than storm sewers, and they are not designed to transport storm water. In areas with basements, backups of raw sewage can occur if excessive storm water is allowed into a sanitary sewer system. The result is that the oxygen content of the water will be decreased. Those biochemical reactions create what is measured in the laboratory as the Biochemical oxygen demand BOD.
Such chemicals are also liable to be broken down using strong oxidizing agents and these chemical reactions create what is measured in the laboratory as the Chemical oxygen demand COD. Both have been widely adopted as a measure of pollution effect. The so-called 5-day BOD measures the amount of oxygen consumed by biochemical oxidation of waste contaminants in a 5-day period.
The total amount of oxygen consumed when the biochemical reaction is allowed to proceed to completion is called the Ultimate BOD. The Ultimate BOD is very time consuming, so the 5-day BOD has almost universally been adopted as a measure of relative pollution effect. It is possible to develop such correlations for specific waste contaminants in a specific waste water stream but such correlations cannot be generalized for use with any other waste contaminants or waste water streams. This is because the composition of any waste water stream is different.
As an example and effluent consisting of a solution of simple sugars that might discharge from a confectionery factory is likely to have organic components that degrade very quickly. However a final effluent of a sewage treatment works serving a large industrialized area might have a discharge where the ultimate BOD was much greater than the 5 day BOD because much of the easily degraded material would have been removed in the sewage treatment process and many industrial processes discharge difficult to degrade organic molecules.
The laboratory test procedures for the determining the above oxygen demands are detailed in many standard texts. Access to either of these is typically through a manhole. During high precipitation periods a sanitary sewer overflow can occur, causing potential public health and ecological damage Sewage may drain directly into major watersheds with minimal or no treatment.
When untreated, sewage can have serious impacts on the quality of an environment and on the health of people. Pathogens can cause a variety of illnesses. Some chemicals pose risks even at very low concentrations and can remain a threat for long periods of time because of bioaccumulation in animal or human tissue.
These effects on nutrients can have large effects on the biological life in the water in contact with the effluent. Treatment ponds can include any of the following: Oxidation ponds, which are aerobic bodies of water usually 12 meters in depth that receive effluent from sedimentation tanks or other forms of primary treatment.
Polishing ponds are similar to oxidation ponds but receive effluent from an oxidation pond or from a plant with an extended mechanical treatment. Raw sewage lagoons or sewage lagoons are aerobic ponds where sewage is added with no primary treatment other than coarse screening. Anaerobic lagoons are heavily loaded ponds. Sludge lagoons are aerobic ponds, usually meters in depth, which receive anaerobically digested primary sludge, or activated secondary sludge under water.
Phosphorous limitation is a possible result from sewage treatment and results in flagellate-dominated plankton, particularly in summer and fall. High nutrient concentration leads to high chlorophyll a concentrations, which is a proxy for primary production in marine environments.
High primary production means high phytoplankton populations and most likely high zooplankton populations because zooplankton feed on phytoplankton. Filterable solid. Dissolved oxygen: The D. Interference due to nitrate can be eliminated by adding sodium azide to the alkelene potassium iodide solution. The D. This is measured by D. Biochemical Oxygen Demand B. In the biological degradation of sewage and other wastes caused by various types of living organisms or bacteria organic matter is converted into fragments consisting of acetic acid.
When sufficient oxygen is present such as in aerobic system. Oxygen is reduced while the organic matter is oxidised into CO2 and water. When sufficient amount of oxygen is not available i. When oxygen is absent i.
The amount of oxygen required by a mixed population of micro-organisms on oxidising organic matter present in a sample, under strictly aerobic conditions, is generally known as B. The dilution water is prepared by passing air in distilled water for 1 — 2 days so as to make it saturated by dissolved oxygen. The sample so diluted is taken in two bottles. The B. Measurement of D. If the sample does not contain any oxygen, it is supplied with oxygen and the depletion caused is calculated as the B.
Microbial organisms or seed may also have to provided B. Chemical Oxygen Demand C. The organic matter in the sample is related as the oxygen required C. The C. In comparison to B. Chemical oxygen demand is the amount of oxygen consumed under specified condition in the oxidation of organic and oxidisable inorganic matter connected for the influence of chlorides. Silver sulphate as catalyst and mercuric sulphide.
The organic matter of the aliquot sample is oxidized to water, CO2 and ammonia. The excess dichromate remaining unreacted in the solution water standard solution of 0. Where V1 and V2 are the volume of ferrous ammonium sulphate run down in the blank and test experiments. One sample volume of the sample taken for the test.
Project Report 4. Stages of Waste Water Treatment: Waste water, whether domestic or industrial have several undesirable components, the organic and inorganic pollutants that are potentially harmful to the environment and human health. The treatment of waste water and its proper management has become a necessity in order to conserve this vital resource. The main aim of waste water treatment is the removal of contaminants from water so that the treated water can be reused for beneficial purposes.
The waste water treatment is carried out in three stages: Primary, Secondary and Tertiary or advanced waste treatment. Primary Treatment: Waste water, contains a wide variety of solids of various shapes, sizes and densities. The primary treatment is of general nature and is used for removing suspended solids, odour, colour and to neutralize the high or low pH in the case of industrial effluents. This stage exploits the physical or chemical properties of the contaminants and removes the suspended and floating matter by screening, sedimentation, floatation, filtration, precipitation etc.
Coarse solids consist of sticks, rags, boards and other large objects that often and inexplicably, find their way into waste water collection systems.
Because the primary purpose of screens is to protect pumps and other mechanical equipment and to prevent clogging of valves and other appurtenances in the waste water plant, screening is normally the first operation performed on the incoming waste water. Waste water screens are classified as coarse or fine, depending on their construction. Coarse screens usually consist of Vertical bars spaced mm apart and inclined away from the incoming flow. Solids retained by the bare are usually removed by manual raking in small plants, while mechanically cleaned units are used in larger plants.
Fine screening mm consist of woven-wire cloth or perforated plates mounted on rotating disk or drum partially submerged in the flow, or on travelling belt. The quantity of solids removed by screening depends on screen-opening size. A hammer mill device is most often used for this purpose. Most often; a shredding device called a comminutor is located across the flow path and intercepted the coarse solids and shreds them to approx.
These solids remain in the waste water. Many kinds of comminutes are available. More complex clarifiers also have skimmers to simultaneously remove floating grease like soap scum and solids like feathers or wood chips. Containers like the API oil-water separator are specifically designed to separate non-polar liquids. Other types of water filters remove impurities by chemical or biological processes described below. Secondary treatment converts organic compounds into carbon dioxide , water, and biosolids.
Chemical oxidation is widely used for disinfection. Aeration tank of an activated sludge process at the wastewater treatment plant in Dresden-Kaditz, Germany Main article: Secondary treatment Secondary treatment by biochemical oxidation of dissolved and colloidal organic compounds is widely used in sewage treatment and is applicable to some agricultural and industrial wastewaters.
Biological oxidation will preferentially remove organic compounds useful as a food supply for the treatment ecosystem. Concentration of some less digestible compounds may be reduced by co-metabolism.
Removal efficiency is limited by the minimum food concentration required to sustain the treatment ecosystem. These treatments may also be used independently for some industrial wastewater. Chemical reduction or pH adjustment minimizes chemical reactivity of wastewater following chemical oxidation. Wastewater treatment plants[ edit ] For plant species utilized in water treatment, see Organisms involved in water purification.
Wastewater treatment plants may be distinguished by the type of wastewater to be treated, i. Overview of the wastewater treatment plant of Antwerpen-Zuid, located in the south of the agglomeration of Antwerp Belgium Sewage treatment plants[ edit ] Main article: Sewage treatment plant A typical municipal sewage treatment plant in an industrialized country may include primary treatment to remove solid material, secondary treatment to digest dissolved and suspended organic material as well as the nutrients nitrogen and phosphorus, and — sometimes but not always — disinfection to kill pathogenic bacteria.
The sewage sludge that is produced in sewage treatment plants undergoes sludge treatment. Larger municipalities often include factories discharging industrial wastewater into the municipal sewer system.
A study done in Britain found that the quality of effluent affected the plank tonic life in the water in direct contact with the wastewater effluent.
Such chemicals are also liable to be broken down using strong oxidizing agents and these chemical reactions create what is measured in the laboratory as the Chemical oxygen demand COD. Any liquid used to boil pasta, for example, may be recycled as water for plants rather than dumping the used water into the sink. In comparison to B. The settled and floating materials are removed and the remaining liquid may be discharged or subjected to secondary treatment. The population of microorganisms in an aerated lagoon is much lower than that in an actual sludge system because there is no sludge recycle. It is also widely used for the treatment of other wastewaters.
It is also widely used for the treatment of other wastewaters.
The influent is sprinkled over the bed packing See Fig. Project Report 4. At the simplest level, treatment of sewage and most wastewaters is carried out through separation of solids from liquids , usually by sedimentation. When sufficient amount of oxygen is not available i. However, effluent released into marine systems also leads to greater population instability.
Another device, called a barminutor, uses a vertical bars screen with a cutting head that travels up and down, the rack of bars, shredding the intercepted material. Flotation technique is used in paper industry to recover fine fibres from the screened effluent and in the oil industry for the classification of oil bearing waste. Some jurisdictions require storm water to receive some level of treatment before being discharged directly into waterways. Many configurations of grit tanks are available. In addition, heavy storms that contribute greater excess flow than the treatment plant can handle may overwhelm the sewage treatment system, causing a spill or overflow. A wide variety of methods are used in advanced waste treatment, which includes the removal of: a Suspended solids,.
Anaerobic processes are widely applied in the treatment of industrial wastewaters and biological sludge. Suspended-Growth systems include activated sludge, where the biomass is mixed with the sewage and can be operated in a smaller space than fixed-film systems that treat the same amount of water. Trickling filters are also called percolating filters. Examples of treatment processes used for storm water include retention basins, wetlands, and buried vaults with various kinds of media filters, and vortex separators to remove coarse solids. Since there is a main pattern in the cycles that occurred simultaneously at all stations it indicates seasonal factors temperature, solar radiation, and phytoplankton control of the bacterial population. Since disposal or reuse are the objectives of wastewater treatment, disposal or reuse options are the basis for treatment decisions.
The bacteria and protozoa consume biodegradable soluble organic contaminants e. In areas with basements, backups of raw sewage can occur if excessive storm water is allowed into a sanitary sewer system. This is because the composition of any waste water stream is different.
The most common example of wastewater is liquid sewage. The physical infrastructure, including pipes, pumps, and screens, channels etc. The plank tonic trend of high populations close to input of treated sewage is contrasted by the bacterial trend. Coarse solids consist of sticks, rags, boards and other large objects that often and inexplicably, find their way into waste water collection systems.
If the sample does not contain any oxygen, it is supplied with oxygen and the depletion caused is calculated as the B. Coarse screens usually consist of Vertical bars spaced mm apart and inclined away from the incoming flow.
At the simplest level, treatment of sewage and most wastewaters is carried out through separation of solids from liquids , usually by sedimentation.
Since there is a main pattern in the cycles that occurred simultaneously at all stations it indicates seasonal factors temperature, solar radiation, and phytoplankton control of the bacterial population. Stationary teeth then shred material that is intercepted by the screen. When oxygen is absent i. Here sulphuric acid is added in the effluent till pH becomes almost 7.