Читать книгу Automation of Water Resource Recovery Facilities - Water Environment Federation - Страница 244

Sludge that reaches the bottom of a primary clarifier is typically raked to a sump area from which it can be piped for removal. Often, there are valves outside the tank that control removal. Most systems have pumps following the valves to pump sludge to the solids processing portion of the facility. Many systems have the ability to valve more than one tank to the same pump. Typically, sludge needs to have at least some thickening within the primary clarifier to avoid overloading downstream solids processing systems. However, if the sludge is allowed to become too thick, it may cause the sludge removal mechanism to overload. In addition, the sludge cannot become too thick for the sludge pump to handle. Therefore, the amount of time that the sludge remains in the primary clarifier should be limited to avoid septic conditions in the primary clarifier.