7-OSST_Alternative-Waste-Systems PDF

# OSST/ALTERNATIVE WASTE SYSTEM ## Basic Mechanical Engineering Engr. Oscar Dean Villaverde, MEngME, MMEngM, RMEE, SO2 CEN-ME Southern Luzon State University ## Wastewater - Wastewater contains the waste products, excrement, or other discharge from the bodies of human beings or animals, and ot...

# OSST/ALTERNATIVE WASTE SYSTEM ## Basic Mechanical Engineering Engr. Oscar Dean Villaverde, MEngME, MMEngM, RMEE, SO2 CEN-ME Southern Luzon State University ## Wastewater - Wastewater contains the waste products, excrement, or other discharge from the bodies of human beings or animals, and other noxious or poisonous substances that are harmful to the public health, or to animal or aquatic life, or to the use of water for domestic water supply or for recreation. - It is a combination of the liquid and water-carried wastes from residences, commercial buildings, Industrial plants, and institutions, together with any groundwater, surface water and Storm water that has infiltrated the public sewage System. ## Wastewater ** Domestic Wastewater** - Wastewater from residences, apartments, motels, office buildings, and other similar types of buildings. There are two types of domestic water: gray water and black water. - **Gray water** is wastewater that typically contains the residues of washing processes. It is generated in the bathtub, shower, sink, lavatory, and clothes washing machine. - **Black water** is wastewater that contains fecal matter and urine. It is produced in water closets (toilets), urinals, and bidets. **Commercial Wastewater** - Commercial wastewater is nontoxic, nonhazardous wastewater from commercial and institutional food service operations and beauty salons. It is usually similar in composition to domestic wastewater, but may occasionally have one or more of its constituents exceed typical domestic ranges. **Industrial Wastewater** - Industrial wastewater is process and nonprocess wastewater from manufacturing, commercial, laboratory, and mining operations, including the runoff from areas that receive pollutants associated with industrial or commercial storage, handling, or processing. ## Wastewater Constituents - Wastewater is mostly water by weight. - Wastewater released by residents, business, and industries is approximately 99.94% water. Only about 0.06% of the wastewater is dissolved and suspended solid. - The wastewater constituents of most concerns are those that have the potential to cause disease or detrimental environmental effects. These include the following: - Organisms - Pathogens - Organic Matter - Oil and Grease - Inorganics - Nutrients - Solids - Gases ## On-Site Sewage Treatment(OSST) - On-site sewage treatment (OSST) systems, traditionally called septic systems, usually consist of the building sewer, which leads from the building into a septic tank and then into a distribution box that feeds the fluid (effluent) into a drainage field or disposal field. - OSST systems treat wastewater from rural and suburban homes, mobile home developments, apartments, schools, retail facilities, and businesses that do not have access to a community wastewater treatment and disposal system. ## An OSST system consists of a primary treatment component, such as a septic tank, and a disposal component, which is typically the drainage field. - Household and human wastes flow in a pipe from the building’s sanitary drainage system to the septic tank. - Inside the septic tank, anaerobic and aerobic bacteria convert the waste into minerals, gas and liquid waste called the effluent - Clarified effluent leaves the septic tank and flows in a pipe to a drainage field. ## Primary Treatment Equipment - Wastewater from a building is first treated in primary treatment equipment such as tanks or filters. In the primary treatment process, anaerobic digestion and settlement of solids in wastewater takes place. ## Septic Tank - The septic tank is a watertight, covered container designed to settle out and hold solid wastes and partially treat wastewater with beneficial bacteria. - It allows heavier solids to settle to the bottom of the tank and lighter particles such as grease and soap float to the top of the tank. - The lighter particles form a layer known as the scum - The remaining solids accumulate as sludge in the bottom of the tank ## Aerobic Tank - Aerobic tanks are a substitute for a septic tank. They consist of a trash tank, an aeration chamber, and a settling chamber. - Premanufactured aerobic tanks use wastewater treatment processes similar to municipal wastewater treatment processes. The clarified effluent is then usually discharged into a drainage field. ## Pump Tank - A pump tank is a watertight container used to temporarily store clarified effluent before it flows into a drainage field. - Wastewater is first treated in an aerobic or septic tank. The effluent then flows by gravity into the pump tank. - When the level of stored effluent reaches a preset elevation, a float switch turns on the pump. The pump discharges the effluent to the drainage field several times a day. - Pump tank materials are typically concrete; plastic (fiberglass and polyethylene) tanks are also used. ## Sand Filters - A sand filter is a lined, impermeable container containing a bed of granular material that provides additional treatment of effluent as it flows from the primary treatment tank to the drainage field. They are usually placed underground with the top surface covered with grass. At sites that have near-surface bedrock or a high water table, sand filters are usually constructed with aboveground concrete walls. ## Trash/Grease Tank - A trash tank is occasionally used in conjunction with an aerobic tank. The trash tank removes materials that treatment microorganisms are unable to degrade. - Grease tanks are used with septic and aerobic tanks, usually in commercial applications. ## Cesspool - A cesspool is a covered underground container that receives untreated sewage directly from a building and discharges it into soil. Openings in the cesspool walls allow untreated sewage to pass through and seep into the surrounding soil. - Because of health concerns tied to the discharge of raw sewage, use of a cesspool is considered unacceptable today in most applications in developed countries. ## Types of On-Site Sewage Treatment 1. **Septic Tank Systems** - This is the most common type of on-site sewage system. - It consists of a septic tank, which is a large underground container where wastewater from the building is stored and partially treated. - Heavy solids settle to the bottom of the tank while greases and lighter solids float to the top. The solids stay in the tank while the wastewater is discharged to the drainfield for further treatment and dispersal. 2. **Aerobic Treatment Unit(ATU)** - Aerobic Treatment Unit use many of the same processes as a municipal sewage plant, but on a smaller scale. - An aerobic system injects oxygen into the treatment tank. - The additional oxygen increases natural bacteria activity within the system that then provides additional treatment for nutrients in the effluent. - Some aerobic systems may also have a pretreatment tank and a final treatment tank including disinfection to further reduce pathogen levels. 3. **Mound System** - Mound systems are an option in areas of shallow soil depth, high groundwater, or shallow bedrock. - The constructed sand mounds contains a drainfield trench. - Effluent from the septic tank flows to a pump chamber where it is pumped to the mound in prescribed doses. - Treatment of the effluent occurs as it discharges to the trench and filters trough the sand, and then disperses into the native soil. 4. **Drip Disribution System** - The drip distribution system is a type of effluent dispersal that can be used in many types of drainfields. - The main advantage of this system is that no large mound of soil is needed as the drip laterals are inserted into the top 6 to 12 inches of soil. - The disadvantage of the drip distribution system is that it requires a large dose tank after the septic tank to accommodate the timed dose delivery of wastewater to the drip absorption area. 5. **Conventional System** - A decentralized wastewater treatment system consisting of a septic tank and a trench or bed surface wastewater infiltration system (drainfield). - A conventional septic system is typically installed at a single-family home or small business. - The gravel/stone drainfield is a design that has existed for decades. - The effluent is piped from the septic tank to a shallow underground trench of stone or gravel. - A geofabric or similar material is then placed on top of the trench so sand, dirt, and other contaminants do not enter the clean stone. 6. **Chamber System** - This type of system consist of a series of connected chambers. - The area around and above the chambers is filled with soil. - Pipes carry wastewater form the septic tank to the chambers. - Inside the chambers, the wastewater comes into contact with the soil. - Microbes on or near the soil treat the effluent. 7. **Recirculating Sand Filter System** - Sand filter systems can be constructed above or below ground. - Effluent flows from the septic tank to a pump chamber. - It is then pumped to the sand filter. - The sand filter is often PVC-lined or a concrete box filled with a sand material. - Effluent is pumped under low pressure through the pipes at the top of the filter. - The effluent leaves the pipes and is treated as it filters though the sand. - The treated wastewater is then discharged to the drainfield. 8. **Evapotranspiration System** - Evapotranspiration systems have unique drainfields. - The base of the evapotranspiration system drainfield is lined with a watertight material. - After the effluent enters the drainfield, it evaporates into the air. - Unlike other septic systems designs, the effluent never filters to the soil and never reaches groundwater. 9. **Constructed Wetland System** - A constructed wetland mimics the treatment processes that occur in natural wetlands. - Wastewater flows from the septic tank and enters the wetland cell. - The wastewater then passes through the media and is treated by microbes, plants, and other media that remove pathogens and nutrients. - The wetland cell typically consists of an impermeable liner, and gravel and sand fill, along the with the appropriate wetland plants, which must be able to survive in a perpetually saturated environment. 10. **Cluster/Community System** - A cluster decentralized wastewater treatment system is under some form of common ownership and collects wastewater from two or more dwellings or buildings. - It conveys the wastewater to a treatment and dispersal system located on a suitable site near the dwelling or buildings. - It is common to find cluster systems in places like rural subdivisions. ## SEPTIC TANK - Septic tank is a receptacle or vault used to collect organic waste discharged from the house sewer. - The main function of a septic tank is to liquefy and precipitate solid waste purifying odorous materials. - Septic tanks are constructed of concrete, metal, fiberglass, or plastic (fiberglass and polyethylene) and are commonly placed underground with the top surface covered with grass. - An access cover built into the top of the tank allows periodic inspection and removal of sludge and scum that collects in the tank. ## Construction of Septic Tank - Septic Tank is constructed from either of the following materials:, - Reinforced concrete - Plastered concrete hollow blocks - Prefabricated asbestos - Thin metal and plastic - The most popular and widely used material for construction of septic tank is plastered hollow blocks or reinforced concrete. Others have not gained acceptance due to cost and durability. ## General Conditions in Constructing a Septic Tank 1. The concrete or masonry septic tank is usually constructed in rectangular form. The reason is to retard the even flow of the waste, which is necessary, to avoid disturbing the decomposition processes inside the tank. 2. The minimum inside dimension of a septic tank is 90 cm wide by 150 cm long. 3. For effective decomposition of the organic materials inside the septic tank, a 120 cm depth of the liquid content is necessary. It is not impractical though, to construct a tank of greater depth, provided that the depth should not be deeper than the natural ground water table. 4. The inlet and outlet inverts of the septic tank shall be long turn sanitary tee. The inverts are installed in the wall of the tank at least 120 cm from its bottom floor equally spaced from both sides. 5. The invert is extended down the liquid of the tank not more than 30 cm. this is to assure smooth delivery of the incoming sewage below the scum line. Scum refers to the lighter organic materials that rises to the surface of the water. 6. The bottom of the digestion chamber should be sloped to one low point. The purpose is to gather the settles organic materials into one mass to favor the propagation of the anaerobic bacteria. 7. The septic tank, should be provided with a manhole, extended a few centimeters above the surface of the soil to overcome infiltration of surface water. This manhole will serve the purpose of cleaning, inspection and repair of the tank. 8. Septic tank for large plumbing installations are provided with suspended compartment attached to the ceiling slab of the tank. The baffle plate is extended down the bottom of the tank about 40 centimeters below the scum line. Each compartment of the tank separated by baffle plate is provided with manhole. 9. The Septic Tank, should be constructed near the surface of the ground, because the correction of the waste depends upon the extent of oxidation and the existence of anaerobic bacteria. Another kind of bacteria that split and digest the effluent is the aerobic bacteria. A kind of bacteria that survive only in the subsoil not more than 150 centimeters below the surface. Oxidation of the effluent deeper than 150 cm would become extremely difficult. - **SIZE OF SEPTIC TANK** So far, there is no mathematic formula ever formulated to arrive in determining a definite size of a septic tank. However, sanitary authorities agreed in principles that: 1. For a family of 6 persons, the minimum tank capacity should be approximately 1.3 cubic meters with a minimum size of 90 centimeters wide by 150 centimeters long and 120 centimeters depth. 2. A very large tank is not advisable, because the bacterial activities would be retarded. The size of the tank is proportionally based on the number of persons expected to be served. In other words, the volume of the tank has a rational proportion with the volume of incoming waste for bacterial activities to be in favorable condition. 3. For residential installation, the practice is to allow 5 to 6 cubic feet of tank volume per person. Thus, a septic tank that will serve a family of 12 persons must have a liquid capacity of 6 x 12 = 72 cubic feet or 538 gallons. (one cubic foot is 748 gallons) - **LOCATION OF SEPTIC TANK** Location of the septic tank shall observe the following considerations: 1. The septic tank may be located closer to the building it will serve, providing a minimum distance of 2 meters from the outside wall. 2. As much as possible, the septic tank should not be located closer to the doors or windows. 3. Septic tank should be at least 15 meters away from any source of water supply. The farther the better. ## REQUIREMENTS FOR A SATISFACTORY DISPOSAL OF HUMAN WASTE 1. There should be no contamination of ground surface that may enter into the spring or wells. 2. There should be no contamination of surface water. 3. The surface soil should not be contaminated. 4. Excreta should not be accessible to animals, flies, cockroaches, vermin and the like. 5. There should be no odor and unsightly conditions. ## SAFETY PRECAUTIONS In most cases septic tanks are poorly aerated or ventilated. It lacks free oxygen. Under this condition, an individual entering into septic tank for making repairs or cleaning purposes, may meet almost instant death. Septic tank may contain harmful and dangerous gases When repair work or cleaning is to be made, be sure that the septic tank is well ventilated, by removing the manhole cover few days in advance of the work. Another precaution is to supply fresh air inside the tank, while work is being done. Remember that the tank may contain inflammable gases that might be ignited to cause a terrific explosion. If light is needed to work in the dark, an electric emergency light with properly insulated cord should be used. In the absence of electric supply, a flashlight powered by dry cell battery is equally safe.