b'How It WorksAerobic Treatment System: Anaerobic Treatment System: Septic / Pretreatment Tank: The septic orThe domestic sewage that discharges down the pretreatment tank should be constructed to maximizebuilding sewer is composed of water and waste matter. the amount of solids it separates. The tank can beThere are two types of waste matter, suspended solids single or double compartments and made of precastlike coffee grounds and dissolved solids like sugar in concrete (5000 psi@28 days). Adequate access must becoffee. This sewage will quickly clog all but the most provided to each compartment for easy accessibility,porous gravel soil formations.inspection, and cleaning. The septic/pretreatment tank shall be constructed in conformance to ASTM-C1227A major function of a septic tank is to remove as many and local/state requirements. solids as possible from the sewage. The out owing liquid (efuent) will nally be distributed over an Aerobic Treatment Plant: The treatment plant is aadequate area of land where it can be dispersed in pre-engineered treatment tank that utilizes aerobica soil absorption eld. The absorption eld is usually (oxygen using) action to break down raw sewage.a series of parallel trenches, each containing a This system consists of a concrete or berglass mixingdistribution pipe embedded in drain eld gravel. tank, an internal cone shaped settling chamber, andThe efuent drains out through holes in the pipe into air injection equipment. The injected air enablesthe gravel bed, and then into the soil. The soil lters naturally occurring bacteria to thrive and grow inremaining minute solids and pathogens (disease- much greater numbers than would occur naturally.producing microorganisms). Water and dissolved This overpopulation of bacteria speeds the processsubstances slowly percolate outward into the soil of breaking down the sewage. and down toward ground water or restrictive layer. Some of the water evaporates or is used by plants.The raw sewage enters the mixing chamber where mixing occurs through an air distribution system.A second function of the septic tank is to treat the The solids remain in suspension with a general owsolids remaining in the tank with bacteria of the up the mixing tank wall and down the outside of theanaerobic species (only active in the absence of settling chamber. The mixed liquid then enters theoxygen). Given enough time, these bacteria decompose settling chamber from the bottom. The settlingthe solids, and eventually make them stable. This chamber maintains a quiet condition that allows solidsdecomposition or treatment of the sewage under to settle down and re-enter the mixing chamber foranaerobic conditions is termed putrefaction or more processing. The liquid is hydraulically displacedseptic hence the name of the tank.upward and is discharged as clear odorless treated water that meets or exceeds state water qualityA third function of the tank is to store the solids. A rock standards. Treatment tanks must meet stringentis chemically stable, whereas an orange, for example, specications and are ANSI/NSF 40 Certiedis unstable because bacteria and fungus can and state approved. decompose it until it is stable and is no longer subject to bacterial action. This process of bacterial breakdown Pump/ Dosing Tanks: The sewage discharge fromis called digestion. There are three layers in the tank. the treatment tank gravity ows into the pump tank.These include sludge at the bottom (heavier solids that The pump tank is constructed of concrete or berglass.have settled), scum at the top (fats and greases, light The tank contains either one (simplex) or two (duplex)solids that have risen), and in-between, relatively clear submersible pumps. When the level rises to a set levelsewage that still contains sugars, detergents, the pump(s) will pump the treated sewage to anand other dissolved solids.absorption bed, drip irrigation eld or above ground sprayers. The pump(s) is controlled with oat switches,The anaerobic bacteria work in all three layers. These control panel and a timer. bacteria reduce the size and weight of the solids by turning a large part of them into liquids and gases. Chlorinator: If the treated sewage needs furtherThus, a pound of solids entering a tank may be only treatment, a chlorinator is employed to add smalla fraction of the weight three months later. Every time amounts of chlorine to the efuent. This chlorine willraw sewage enters the tank, it forces an equal amount kill in remaining pathogens. The chlorinator is generallyof treated sewage out of the tank. Septic tank tees or used for above ground disposal. The chlorinator usesbafes prevent the sludge and top scum layer from chlorine tablets that are dissolved in the efuentexiting the tank with the treated sewage. The sewage ow stream. efuent leaving the tank may still contain pathogens and are dispersed into the soil absorption drain eld. Visit ossf.parkusa.com for more information andBacteria present in the soil carry out further digestion.design assistance.APPLICATIONSGood to useCommercial Residential HotelsMulti Story in BMPsFamily Home'