It is essential that the design of any treatment process is based on a full planning to install or upgrade a water treatment process should seek expert guidance. Application of specialized water treatment processes: • Hardness treatment This lesson on water treatment focuses on the reasons for treatment, the basic pro-. A community should be consulted when choosing a water-treatment system and should . as the water temperature reaches 50 °C, the inactivation process is.

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Lecture 8: Water treatment processes. Objective: Understand functioning of different unit processes for water treatment. Courtesy: Dr. Irene. Choice of Water Treatment Process. Choice of treatment process depends on: Quality of raw water: Water source. Period of design year. R. i d lit f t t d t (d.). Water Treatment Plants have many Figure 1 WATER TREATMENT PROCESS .. kaz-news.info

Fixed-film or attached growth systems include trickling filters , constructed wetlands , bio-towers, and rotating biological contactors , where the biomass grows on media and the sewage passes over its surface. However, fixed-film systems are more able to cope with drastic changes in the amount of biological material and can provide higher removal rates for organic material and suspended solids than suspended growth systems.

Tertiary treatment[ edit ] The purpose of tertiary treatment is to provide a final treatment stage to further improve the effluent quality before it is discharged to the receiving environment sea, river, lake, wet lands, ground, etc. More than one tertiary treatment process may be used at any treatment plant.

If disinfection is practised, it is always the final process. It is also called "effluent polishing.

These lagoons are highly aerobic and colonization by native macrophytes , especially reeds, is often encouraged. Small filter-feeding invertebrates such as Daphnia and species of Rotifera greatly assist in treatment by removing fine particulates. Biological nutrient removal[ edit ] Biological nutrient removal BNR is regarded by some as a type of secondary treatment process, [2] and by others as a tertiary or "advanced" treatment process. Wastewater may contain high levels of the nutrients nitrogen and phosphorus.

Excessive release to the environment can lead to a buildup of nutrients, called eutrophication , which can in turn encourage the overgrowth of weeds, algae , and cyanobacteria blue-green algae. This may cause an algal bloom , a rapid growth in the population of algae.

The algae numbers are unsustainable and eventually most of them die. The decomposition of the algae by bacteria uses up so much of the oxygen in the water that most or all of the animals die, which creates more organic matter for the bacteria to decompose. In addition to causing deoxygenation, some algal species produce toxins that contaminate drinking water supplies. Different treatment processes are required to remove nitrogen and phosphorus.

Nitrogen removal[ edit ] Nitrogen is removed through the biological oxidation of nitrogen from ammonia to nitrate nitrification , followed by denitrification , the reduction of nitrate to nitrogen gas. Nitrogen gas is released to the atmosphere and thus removed from the water. Nitrification itself is a two-step aerobic process, each step facilitated by a different type of bacteria.

Denitrification requires anoxic conditions to encourage the appropriate biological communities to form. It is facilitated by a wide diversity of bacteria. Sand filters, lagooning and reed beds can all be used to reduce nitrogen, but the activated sludge process if designed well can do the job the most easily.

This can be, depending on the waste water, organic matter from feces , sulfide , or an added donor like methanol. The sludge in the anoxic tanks denitrification tanks must be mixed well mixture of recirculated mixed liquor, return activated sludge [RAS], and raw influent e.

Water Treatment Plant Process

Sometimes the conversion of toxic ammonia to nitrate alone is referred to as tertiary treatment. Over time, different treatment configurations have evolved as denitrification has become more sophisticated. An initial scheme, the Ludzack—Ettinger Process, placed an anoxic treatment zone before the aeration tank and clarifier, using the return activated sludge RAS from the clarifier as a nitrate source.

Influent wastewater either raw or as effluent from primary clarification serves as the electron source for the facultative bacteria to metabolize carbon, using the inorganic nitrate as a source of oxygen instead of dissolved molecular oxygen. This denitrification scheme was naturally limited to the amount of soluble nitrate present in the RAS. Nitrate reduction was limited because RAS rate is limited by the performance of the clarifier. The "Modified Ludzak—Ettinger Process" MLE is an improvement on the original concept, for it recycles mixed liquor from the discharge end of the aeration tank to the head of the anoxic tank to provide a consistent source of soluble nitrate for the facultative bacteria.

In this instance, raw wastewater continues to provide the electron source, and sub-surface mixing maintains the bacteria in contact with both electron source and soluble nitrate in the absence of dissolved oxygen.

Many sewage treatment plants use centrifugal pumps to transfer the nitrified mixed liquor from the aeration zone to the anoxic zone for denitrification. At times, the raw or primary effluent wastewater must be carbon-supplemented by the addition of methanol, acetate, or simple food waste molasses, whey, plant starch to improve the treatment efficiency. These carbon additions should be accounted for in the design of a treatment facility's organic loading.

Use of an anaerobic tank following the initial anoxic process allows for luxury uptake of phosphorus by bacteria, thereby biologically reducing orthophosphate ion in the treated wastewater. Even newer improvements, such as Anammox Process, interrupt the formation of nitrate at the nitrite stage of nitrification, shunting nitrite-rich mixed liquor activated sludge to treatment where nitrite is then converted to molecular nitrogen gas, saving energy, alkalinity, and secondary carbon sourcing.

Phosphorus removal is important as it is a limiting nutrient for algae growth in many fresh water systems. For a description of the negative effects of algae, see Nutrient removal.

It is also particularly important for water reuse systems where high phosphorus concentrations may lead to fouling of downstream equipment such as reverse osmosis.

Phosphorus can be removed biologically in a process called enhanced biological phosphorus removal. In this process, specific bacteria, called polyphosphate-accumulating organisms PAOs , are selectively enriched and accumulate large quantities of phosphorus within their cells up to 20 percent of their mass. When the biomass enriched in these bacteria is separated from the treated water, these biosolids have a high fertilizer value.

Phosphorus removal can also be achieved by chemical precipitation , usually with salts of iron e. Chemical phosphorus removal requires significantly smaller equipment footprint than biological removal, is easier to operate and is often more reliable than biological phosphorus removal.

Some systems use both biological phosphorus removal and chemical phosphorus removal.

The chemical phosphorus removal in those systems may be used as a backup system, for use when the biological phosphorus removal is not removing enough phosphorus, or may be used continuously.

In either case, using both biological and chemical phosphorus removal has the advantage of not increasing sludge production as much as chemical phosphorus removal on its own, with the disadvantage of the increased initial cost associated with installing two different systems. Once removed, phosphorus, in the form of a phosphate-rich sewage sludge , may be dumped in a landfill or used as fertilizer.

Therefore, subsequent aerobic treatment of the anaerobic effluents is usually essential. The final waste matter discharged by the anaerobic treatment includes solubilized organic matter that is acquiescent to aerobic treatment demonstrating the possibility of installing collective anaerobic and aerobic units in series [ 1 ]. Anaerobic digesters Samer [ 9 ] elucidated and illustrated the structures and constructions of the anaerobic digesters and the used building materials.

Samer [ 10 ] developed an expert system for planning and designing biogas plants. Figures 8 to 13 show different types of anaerobic digesters. While Figures 1 4 and 15 show some industrial applications. Table 1 shows the advantages and disadvantages of anaerobic treatment compared to aerobic treatment. Figure 8. Figure 9. Single-stage conventional anaerobic digester [3].

Figure Dual-stage high rate digester [3]. Schematic representation of digester types. Flow-through A—B and contact systems C—F [1]. The upper scheme shows a two-stage anaerobic sludge digester, while the lower scheme shows the conventional sludge digestion plant [1]. Primary digestion tank with screw mixing pump and external heater [1]. Wastewater treatment plant for corn processing industry [8]. By definition, the anaerobic treatment is conducted without oxygen.

It is different from an anoxic process, which is a reduced environment in contrast to an environment without oxygen.

Water Treatment

Both processes are anoxic, but anaerobic is an environment beyond anoxic where the oxidation reduction potential ORP values are highly negative. In the anaerobic process, nitrate is reduced to ammonia and nitrogen gas, and sulfate SO is reduced to hydrogen sulfide H2S. Table 1. The advantages and disadvantages of anaerobic treatment compared to aerobic treatment [ 1 ].

Anaerobic lagoons An anaerobic lagoon is a deep lagoon, fundamentally without dissolved oxygen, that enforces anaerobic conditions. The anaerobic process occurs in deep ground ponds, and such basins are implemented for anaerobic pretreatment. The anaerobic lagoons are not aerated, heated, or mixed. The depth of an anaerobic lagoon should be typically deeper than 2. Such depths diminish the amount of oxygen diffused from the surface, allowing anaerobic conditions to prevail U. EPA, Figures 16 to 18 show different types of anaerobic lagoons.

Anaerobic lagoon for strong wastewater treatment, such as meat processing wastewater [1]. Schematic of volume fractions in anaerobic lagoon design [11]. Anaerobic wastewater treatment lagoon [12]. Precisely, the bioreactor is a vessel in which a biochemical process is conducted, where it involves microorganisms e.

The treatment can be conducted under either aerobic or anaerobic conditions. The bioreactors are commonly made of stainless steel, usually cylindrical in shape and range in size from liters to cubic meters.

The bioreactors are classified as batch, plug, or continuous flow reactors e. Before arriving at the Filtration Facility chlorine is added to the water at the pre-chlorination point to begin the disinfection process. The disinfection process is designed to kill or inactivate most microorganisms in water, including essentially all pathogenic organisms whether they are from bacteria, viruses or intestinal parasites.

Filtration is the process of passing water through material such as a bed of coal, sand, or other granular substance to remove particulate impurities that were not removed during the sedimentation process. The water treatment plant uses rapid rate multi-media gravity filter beds. The filters are comprised of a top layer of anthracite, a middle layer of filter sand and then a bottom layer of garnet sand and one an underdrain system that collects the filtered water. The water enters on top of the filter media and passes down through the filter beds by gravity.

The different materials work like a giant strainer and trap remaining particulates. Potable water is run backwards through the filters releasing the entrapped particulates that are collected in drain troughs.

Water purification

The backwash water is sent to the Backwash Recovery Pond and, after a settling process, the backwash water is returned to the raw water settling pond for re-use. The water that is collected from the bottom of the filters is then considered potable. Before the water leaves the clearwells under the water treatment plant chlorine is added a second time for post-disinfection.

The additional chlorine ensures that the water remains safe to drink even at the furthest reaches of the distribution system. In addition to the chlorine, fluoride is added to our drinking water at the plant. When fluoridated water is drank during the years of tooth development, the fluoride strengthens teeth and prevents tooth decay.

The United States Public Health Service has determined the optimum concentration for fluoride in United States water to be in the range of 0.

Dissolved fluoride-containing minerals are measured year round in the water of the Arkansas River.

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The natural fluoride content of the river water averages. The water treatment plants enough fluoride to raise that level to. The fluoride level is measured daily at the water treatment plant and monthly at the tap to make sure it is sufficient to meet the concentration recommended by USPHS.Automatic pressure filters, where the water is forced under pressure through the filtration system, were innovated in in England.

Organic materials are degraded into basic constituents, finally to methane gas under the absence of an electron acceptor such as oxygen [ 8 ]. Also the use of enzymes such as the enzyme laccase is under investigation. In an experiment, wastewater contaminated with diesel oil was inoculated with mycelia of oyster mushrooms. Water supplies that are particularly vulnerable to unicellular algae blooms and supplies with low turbidity and high colour often employ DAF.

Permanent water chlorination began in , when a faulty slow sand filter and a contaminated water supply led to a serious typhoid fever epidemic in Lincoln, England. Anaerobic digestion is a complex multistep process in terms of chemistry and microbiology. A second pump station lifts the water to the water treatment plant headworks.