please help me sludge collector for sedimentation basin in water supply?

Answer 1

Here is a broad related account,see if it helps,


A. Primary Treatment

The wastewater that enters a treatment plant contains debris that might clog or damage the pumps and machinery. Such materials are removed by screens or vertical bars, and the debris is burned or buried after manual or mechanical removal. The wastewater then passes through a comminutor (grinder), where leaves and other organic materials are reduced in size for efficient treatment and removal later.

1. Grit Chamber

In the past, long and narrow channel-shaped settling tanks, known as grit chambers, were used to remove inorganic or mineral matter such as sand, silt, gravel, and cinders. These chambers were designed to permit inorganic particles 0.2 mm (0.008 in) or larger to settle at the bottom while the smaller particles and most of the organic solids that remain in suspension pass through. Today, spiral-flow aerated grit chambers with hopper bottoms, or clarifiers with mechanical scrapper arms, are most commonly used. The grit is removed and disposed of as sanitary landfill. Grit accumulation can range from 0.08 to 0.23 cu m (3 to 8 cu ft) per 3.8 million liters (about 1 million gallons) of wastewater.

2. Sedimentation

With grit removed, the wastewater passes into a sedimentation tank, in which organic materials settle out and are drawn off for disposal. The process of sedimentation can remove about 20 to 40 percent of the BOD5 and 40 to 60 percent of the suspended solids.

The rate of sedimentation is increased in some industrial waste-treatment stations by incorporating processes called chemical coagulation and flocculation in the sedimentation tank. Coagulation is the process of adding chemicals such as aluminum sulfate, ferric chloride, or polyelectrolytes to the wastewater; this causes the surface characteristics of the suspended solids to be altered so that they attach to one another and precipitate. Flocculation causes the suspended solids to coalesce. Coagulation and flocculation can remove more than 80 percent of suspended solids.

3. Flotation

An alternative to sedimentation that is used in the treatment of some wastewaters is flotation, in which air is forced into the wastewater under pressures of 1.75 to 3.5 kg per sq cm (25 to 50 lb per sq in). The wastewater, supersaturated with air, is then discharged into an open tank; there the rising air bubbles cause the suspended solids to rise to the surface, where they are removed. Flotation can remove more than 75 percent of the suspended solids.

4. Digestion

Digestion is a microbiological process that converts the chemically complex organic sludge to methane, carbon dioxide, and an inoffensive humuslike material. The reactions occur in a closed tank or digester that is anaerobic—that is, devoid of oxygen. The conversion takes place through a series of reactions. First the solid matter is made soluble by enzymes, then the substance is fermented by a group of acid-producing bacteria, reducing it to simple organic acids such as acetic acid. The organic acids are then converted to methane and carbon dioxide by bacteria. Thickened sludge is heated and added as continuously as possible to the digester, where it remains for 10 to 30 days and is decomposed. Digestion reduces organic matter by 45 to 60 percent.

5. Drying

Digested sludge is placed on sand beds for air drying. Percolation into the sand and evaporation are the chief processes involved in the dewatering process. Air drying requires dry, relatively warm weather for greatest efficiency, and some plants have a greenhouselike structure to shelter the sand beds. Dried sludge in most cases is used as a soil conditioner; sometimes it is used as a fertilizer because of its 2 percent nitrogen and 1 percent phosphorus content.

B. Secondary Treatment

Having removed 40 to 60 percent of the suspended solids and 20 to 40 percent of the BOD5 in primary treatment by physical means, the secondary treatment biologically reduces the organic material that remains in the liquid stream. Usually the microbial processes employed are aerobic—that is, the organisms function in the presence of dissolved oxygen. Secondary treatment actually involves harnessing and accelerating nature's process of waste disposal. Aerobic bacteria in the presence of oxygen convert organic matter to stable forms such as carbon dioxide, water, nitrates, and phosphates, as well as other organic materials. The production of new organic matter is an indirect result of biological treatment processes, and this matter must be removed before the wastewater is discharged into the receiving stream.

Several alternative processes are also available in secondary treatment, including a trickling filter, activated sludge, and lagoons.

1. Trickling Filter

In this process, a waste stream is distributed intermittently over a bed or column of some type of porous medium. A gelatinous film of microorganisms coats the medium and functions as the removal agent. The organic matter in the waste stream is absorbed by the microbial film and converted to carbon dioxide and water. The trickling-filter process, when preceded by sedimentation, can remove about 85 percent of the BOD5 entering the plant.

2. Activated Sludge

This is an aerobic process in which gelatinous sludge particles are suspended in an aeration tank and supplied with oxygen. The activated-sludge particles, known as floc, are composed of millions of actively growing bacteria bound together by a gelatinous slime. Organic matter is absorbed by the floc and converted to aerobic products. The reduction of BOD5 fluctuates between 60 and 85 percent.

An important companion unit in any plant using activated sludge or a trickling filter is the secondary clarifier, which separates bacteria from the liquid stream before discharge.

3. Stabilization Pond or Lagoon

Another form of biological treatment is the stabilization pond or lagoon, which requires a large land area and thus is usually located in rural areas. Facultative lagoons, or those that function in mixed conditions, are the most common, being 0.6 to 1.5 m (2 to 5 ft) in depth, with a surface area of several acres. Anaerobic conditions prevail in the bottom region, where the solids are decomposed; the region near the surface is aerobic, allowing the oxidation of dissolved and colloidal organic matter (see Colloid). A reduction in BOD5 of 75 to 85 percent can be attained.

C. Advanced Wastewater Treatment

If the receiving body of water requires a higher degree of treatment than the secondary process can provide, or if the final effluent is intended for reuse, advanced wastewater treatment is necessary. The term tertiary treatment is often used as a synonym for advanced treatment, but the two methods are not exactly the same. Tertiary, or third-stage, treatment is generally used to remove phosphorus, while advanced treatment might include additional steps to improve effluent quality by removing refractory pollutants. Processes are available to remove more than 99 percent of the suspended solids and BOD5. Dissolved solids are reduced by processes such as reverse osmosis and electrodialysis. Ammonia stripping, denitrification, and phosphate precipitation can remove nutrients. If the wastewater is to be reused, disinfection by ozone treatment is considered the most reliable method other than breakpoint chlorination. Application of these and other advanced waste-treatment methods is likely to become widespread in the future in view of new efforts to conserve water through reuse. See Absorption; Osmosis; Precipitation.

D. Liquid Disposal

The ultimate disposal of the treated liquid stream is accomplished in several ways. Direct discharge into a receiving stream or lake is the most commonly practiced means of disposal. In areas of the United States that are faced with worsening shortages of water for both domestic and industrial use, municipalities and state and federal agencies are turning to reuse of appropriately treated wastewater for groundwater recharge, irrigation of nonedible crops, industrial processing, recreation, and other uses. Many reuse projects are located in California, Arizona, and Texas.

The first large-scale wastewater-reclamation plant in the United States is the Denver Water Department's Potable Reuse Demonstration Plant. The one-million-gallon-per-day plant was built to demonstrate the quality, reliability, and economic potential of reuse on a large scale. The quality and health-effects testing program, ended in 1993, after successfully meeting its goal of producing drinkable water from reclaimed water. The reused water was tested against the regular drinking water received by Denver residents and found to be equally drinkable. The treatment process involves conventional primary and secondary treatment followed by lime clarification to remove suspended organic compounds. During this process, an alkaline (high-pH) condition is created to improve the process. In the next step, recarbonation is used to bring the pH level to neutral. Then the water is filtered through multiple layers of sand and charcoal, and ammonia is removed by ionization. Pesticides and any other dissolved organic materials still present are absorbed by a granular, activated-carbon filter. Viruses and bacteria are then killed by ozonization. At this stage the water should be cleansed of all contaminants, but, for added reliability, second-stage carbon adsorption and reverse osmosis are used, and chlorine dioxide is added to attain the highest possible water standard. Similar reuse programs are underway in the southwestern United States, Saudi Arabia, and the Netherlands

Answer 2

it dependson the spead of water and tank area but what is the question