1. Mechanical ventilation of a lift station is required to _. a. lower the temperature b. reduce chlorine demand c. eliminate the presence of harmful gases d. increase D.O. in raw wastewater 2. What is the minimum D.O. to prevent formation of hydrogen sulfide in at a treatment plant? a. 2.0 b. 1.0 c. 0.5…
1. Which of these pH readings indicate an acidic wastewater? a. 3 b. 7 c. 9 d. 12 2. The record log of a hydraulic cleaning operation should include _. a. type and amount of material removed from downstream manhole b. feet of rod used c. camera malfunctions d. all the above 3. What type…
DISSOLVED AIR FLOATATION (DAF) THICKENERS Dissolved air floatation thickening relies on a process similar to what happens to sludge during denitrification. Small air bubbles attach themselves to sludge particles and separate them from the remaining liquid by floating them to the surface where they accumulate into a sludge layer. This sludge layer is skimmed off…
Vacuum Sewer Systems Vacuum sewers have become an acceptable alternative in the proper application and are providing efficient and reliable sewer service to communities all around the world. A vacuum sewer system consists of three major components: the valve pit, the vacuum mains, and the vacuum station. Vacuum sewerage is a mechanized system of wastewater…
Operation and Maintenance or Pressure Sewers Routine operation and maintenance requirements for both septic tank effluent pump and grinder pump systems are minimal. Most system maintenance activities involve responding to homeowner service calls usually for electrical control problems or pump blockages. Septic tank effluent pump systems also require pumping every two to three years. The…
Sludge Thickening and Dewatering Even what is considered a “thick” sludge, (5 – 6% total solids), still contains over 90% water. Storing and transporting all the water along with the solids contained within it is not practical. For this reason, there are a number of methods of separating solids from water. These methods include; gravity…
Aerobic Digestion There is not much involved in the operation of aerobic digesters. Sludge feed rates are based on the need to remove solids from the secondary treatment process. Sludge removal rates are determined by the level in the digester and by the availability of sludge dewatering and drying units. Around 1.0 mg/L D.O. should…
Pressure Sewer Systems (Design Criteria) Many different design flows can be used in pressure systems. When positive displacement grinder pump units are used, the design flow is obtained by multiplying the pump discharge by the maximum number of pumps expected to be operating simultaneously. No allowances for infiltration and inflow are required. No minimum velocity…
Costs The cost of a conventional gravity sewer system varies, based on many factors, including the depth and difficulty of excavation, the cost of labor, availability of pipe, geologic conditions, hydraulic grade line, and construction sequencing. As such, it is difficult to quantify the cost per linear foot for a particular sewer pipe size. Pressure…
Anaerobic Digestion OPERATION OF ANAEROBIC DIGESTERS The key to operating an anaerobic digester lies in balancing the acid formation and methane fermentation processes. This is accomplished by maintaining the desired temperature (95º F), ensuring mixing to promote contact between the organisms and the food as well as promoting even heating. Of high importance is FEEDING…
