Agenda - 10-08-1991 - Laserfiche WebLink

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The.advantage to a discharging sand filter is that it allows the location of a waste treatment system in areas where the land is unsuitable for an on -site system and where there is no municipal system accessible. The recirculating sand filter produces a high quality effluent. Sand filter discharging systems can be reconditioned and repaired, unlike many nitrification fields. The disadvantages to discharging sand filters is that they are expensive to construct and are maintenance intensive. Non- recirculating sand filters produce a low quality effluent. In spray systems, sand filter effluent flows by gravity to a tank where chlorine is added to kill the microbes in the waste water. The waste water is then pumped out.to the spray irrigation field. The spray irrigation field contains sprinklers not unlike rotary lawn sprinklers which spray the liquid waste into the air over the nitrification field. The waste water evaporates into the air and is absorbed by trees, grasses, and the soil. High flow capacity spray irrigation systems can be required to have a holding tank or lagoon, capable of containing the system's entire waste water flow for a thirty day or longer period. This allows the system to operate without using the spray irrigation fields during extended wet weather periods. There are several advantages to a spray irrigation system. it can be used for on -site waste disposal in soils which are unsuitable for conventional or low pressure pipe systems. Spray systems produce a much cleaner effluent than other non - discharging systems. The disadvantages to spray systems involve the additional construction expense, operation and maintenance demands and complexities associated with sand filters and disinfection units. In addition, spray irrigation systems have very small application rates of waste per square foot of nitrification field and require wide buffers around the spray field, which means that these systems can only be used on large tracts of land. Class IV 8 stems - Private Cluster Systems Cluster systems are the first of the classifications outlined in this report which serve multiple or high volume users and which require a waste or sewer collection system or network in addition to a waste treatment system. The sewage is collected at a central point by either gravity, pressurized sewers, or individual STEP systems. From this central facility the treatment and disposal may be a large conventional system, a low pressure pipe, or a spray irrigation system as described in the above sections. The central facility could have a primary treatment unit composed of a series of relatively small septic tanks -each receiving a measured and predetermined portion of total flow, 7