The actual test data for the effluent quality of septic tanks, the removal rate of impurities, and the treatment effectiveness are not as comprehensive as those for water and wastewater treatment facilities. It is necessary to select representative types of buildings in various regions, conduct comprehensive tests on the effluent quality, treatment effectiveness of septic tanks at different times of the day during different seasons, and accordingly...
Regular testing of the composition changes in domestic wastewater is conducted to enrich and perfect the design data, guiding engineering design.
Cleaning Cycle
The cleaning cycle of septic tanks is related to the temperature of fecal wastewater, ambient temperature, nature of the building, and the quality and volume of drainage water. If the designed cleaning cycle is too short, the concentration of fecal sludge in the septic tank will be excessively high, significantly differing from the actual cleaning cycle. This can affect normal fermentation and wastewater treatment, potentially leading to overflow of fecal sludge and environmental impact.
Sanitation. If the cleaning cycle in the design is too long, the septic tank volume will be excessive, increasing the construction cost. The Code for Design of Water Supply and Drainage of Buildings (GBJ15-88) (hereinafter referred to as the "Code") requires a cleaning cycle of 3 to 12 months, with most actual designs opting for 3 to 9 months, and the acid fermentation period in the acidic fermentation stage being 3 months.
In the month, the acid reduction period is about 5 months. Practical experience has proven that the determination of the cleaning cycle should take into account three factors: the wastewater treatment effect, construction cost, and management. The cleaning cycle generally should not be less than 12 months. The Shangyuanmen Waterworks Dormitory Area has a common septic tank for the flat buildings, serving 200 people, with standard domestic wastewater.
Each person generates 30L/day, sludge per person at 0.4L/day, with the fresh sludge moisture content in the septic tank set at 95%, and the moisture content after fermentation at 90%. The design cleaning cycle is chosen to be 12 months, with the calculated septic tank volume being 21m³.
Dwell Time
The detention time in septic tanks is a crucial indicator affecting the effectiveness of wastewater treatment and the volume and cost of the tanks. A short detention time results in poor treatment effectiveness, while an extended one increases the tank's volume and cost, as well as posing difficulties in arrangement. Determining the detention time should balance both the treatment effectiveness and the construction cost.
Two factors on pricing should be considered: the impact of fermentation bubbles on the laminar flow state required for sedimentation, the negative effects of numerous streamline turns in septic tanks on sedimentation, and the significant instantaneous changes in domestic wastewater discharge on the uniformity of incoming water flow. There should be ample leeway for the retention time in the septic tank. "The Specification" requires: retention time
Retrieval interval: 12 to 24 hours. Practical evidence shows that the retention time should not be less than 12 hours to ensure effective wastewater treatment. The septic tank in the dormitory area of the Shangyuanmen Waterworks has a retention time of 24 hours.
Septic tanks are treatment devices that utilize sedimentation and anaerobic fermentation principles to remove suspended organic matter from domestic wastewater. The high-efficiency corrugated fiberglass septic tank is equipped with baffles, with holes misaligned vertically and horizontally, preventing short circuits and dividing the entire tank into three sections: primary anaerobic chamber, secondary anaerobic chamber, and clarification section.
The room features a first and second-grade anaerobic chamber with a common bottom, internally fitted with "MDS Special Type Filler." This separation reduces the contact time between wastewater and sludge, allowing the acidic fermentation and alkaline fermentation processes to be independent of each other. Additionally, the presence of the filler increases the contact surface area between wastewater and sludge, significantly
Enhanced response efficiency.
