Sand Filter Systems
In a sand filter system, sewage flows from the house into one or several septic tanks, depending upon the size of the house and local requirements. Effluent from the septic tank(s) flows into a pump or lift tank. A pump introduces the effluent at the top of the watertight sand filter, using pressure distribution to apply the wastewater evenly to the filter surface to maximize treatment. A timer is used to dose the entire surface of the filter intermittently with wastewater. This draws oxygen from the atmosphere through the sand medium and its attached microbial community. The effluent is treated by physical, chemical, and biological processes. Suspended solids are removed by mechanical straining due to enhanced contact and sedimentation. Treatment occurs through the bacteria that colonize in the sand grains. Microorganisms use the organic matter and nutrients in the effluent for growth and reproduction.
The two main types of sand filters differ in the rate at which wastewater is introduced into the system. Loading rates determine the amount of maintenance needed and how long the system will last. A single-pass filter with a high loading rate needs regular cleaning (every six months to a year) of the sand surface to prevent clogging.
In high-rate sand filters, effluent is applied at rates of 1.6 to 5 gallons per day per square foot. This application rate means the surface of the filter must be easy to access. That is why high-rate sand filters are more common in warmer climates where they can be left open or have a lid that is easily removed.
Low-rate sand filters are the most common designs. Effluent from the pump tank is applied at rates of 0.8-1.5 gallons per day per square foot. Sizing criteria
Quartz sand filter
Quartz sand filter can effectively remove suspended solids in the water and has significant effects on the removal of colloids, iron, organics, pesticides, manganese, bacteria, viruses and other pollutants in the water. besides advantages of small filtration resistance. large specific surface area, strong acid and alkali resistance, resistance to oxidation, PH scope of 2-13 and anti-pollution. As a unique advantages of the quartz sand filter, the filter is able to run self-adaptively through the optimization of the filter media and filter design, so that the filter material has a strong adaptivity to raw water concentration, operating conditions, pre-disposal process. i.e. the filter bed automatically forms a non-uniform state during filtration, which helps to guarantee the water quality under a variety of operating conditions and spread the filter material when backwashing, achieving good cleaning effect. The sand filter has advantages including fast filtering speed, high filtration precision and large interception capacity, etc. The filter is used in the industrial water, domestic water and municipal water systems requiring outflow turbidity of not greater than 5mg/I and complying with drinking water quality standards and for the removal of suspended solid sand solids in industrial wastewater: it can be used as ion exchange and pretreatment for softening desalination system and can also be used in the coarse filtration of water with undemanding industrial water quality, swimming pool circular processing system and cooling circulating water purification system.
Activated carbon filter
Activated carbon filter is used for the removal of color, taste, residual chlorine and organics its main mode of action is adsorption. Activated carbon is an artificial sorbent. Activated carbon has developed pore structure and huge specific surface area, so it has a strong adsorption capacity for the dissolved organics in the water, such as benzene and phenolic compounds, and has better removal efficiency for organic pollutants which are hard to be removed by biological and chemical methods, such as chroma, stench, surfactants, synthetic detergents and dyes, etc. Granular activated carbon is able to remove 85% of Ag A , Cr2 + and Cr04 A 2 in the water Through the activated carbon filter bed, the suspended solid in the water is less than 0.1 mg/L, COD removal rate is generally 40% to 50% and free chlorine is less than 0.1mg/I. It can be used as pretreatment of ion exchange, electrodialysis and reverse osmosis in pure water technology so as to remove organics, colloids and residual chlorine; it can be also used as an advanced treatment mean after the secondary treatment to ensure the quality of reusewater.
Technical parameters sheet for Mechanical sand carbon filter
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