With the rapid development of my country's national economy, sewage treatment plants and other environmental protection projects have increased. Among them, an appropriate number of anaerobic tanks, sludge thickening tanks, and biological flocculation tanks of sewage treatment plants are built around residential areas. The environment of sewage tanks, Style and sewage odor directly affect people's lives and health. Many cities have now required the sewage treatment tanks of sewage plants (stations) to be covered for waste gas collection and management.

There are three current methods for membrane capping of sewage ponds:

1. General carbon steel skeleton sunshine board

2. Stainless steel frame glass steel plate

3. General carbon steel (reverse hanging) membrane material

The steel support part of the above 1 and 2 structural methods is inevitably placed inside the top cover. Due to the doubling of the internal corrosive gas concentration after the top of the pool is covered, the temperature is very high under sunlight radiation, and the internal steel structure is relatively easy to be corroded. The general service life is 3 to 5 years. However, the third membrane system successfully solved this problem by selecting a fluorocarbon fiber membrane with strong corrosion resistance to cover the exhaust gas, so that the steel structure can suspend the outer membrane. In this way, the corrosion problem of steel structure caused by contact with corrosive gas can be solved, and a set of durable waste odor collection system can be formed.

Membrane characteristics:

The membrane is a special membrane for environment. Special modification additives are added to the original PVDF coating to improve the self-cleaning of the membrane and meet the requirements of direct welding. At the same time, the synergistic effect of modification additives and additives in the PVC layer makes the combination of PVDF and PVC coating more firm, not easy to peel off, and no longer need to coat the base material layer. The double-sided PVDF self-cleaning layer not only has excellent protective effect on the top surface of the membrane material, but also has excellent protective effect on the bottom surface. The use of high quality low-yarn high-density polyester yarn, with high-performance anti-capillary, anti-mold additives, can effectively eliminate the film due to side penetration of mold, shedding and other phenomena.

2.2 piping design:

1) Design parameters:

(1) When arranging ventilation pipes, the principles of convenient installation and maintenance, saving investment, and neat and beautiful should be followed;

(2) the outer wall of the ventilation pipe is not less than 150-200mm from the wall; No less than 100-150mm away from beams, columns and equipment and no interface; The spacing between the outer walls of parallel pipes shall not be less than 150-200mm to meet the requirements of construction, operation, maintenance and thermal expansion and cold contraction of pipes.

(3) The relative difference of the pressure loss between the parallel pipe sections of the ventilation system is not more than 15%, and the air valve is used for adjustment when necessary; The calculated pressure loss of the ventilation pipe shall be increased by 10%-15%.

(4) The cutting surface of the ventilation pipe is right circular, and the size is selected according to the "National General Ventilation Pipe Calculation Table": in order to exclude the condensed water in the ventilation pipe, the horizontal pipe is set with a 0.005 slope, and the drainage pipe is set at the bottom of the lowest point.

(5) Considering disassembly and manual handling, the ventilation pipe is made in sections; the air pipes are connected with plastic flanges and sealed with soft nitrile rubber.

(6) In order to reduce wind resistance, the flow channel of the tee, elbow, and reducer adopts an arc shape.

(7) pipe diameter calculation: πr2 = Q/v/3600, where: q is flow rate, unit m3/h; V is flow rate, unit m/s, generally 10~15 m/s.

2) Design principles:

(1) The odor gas collection and transportation system and processing system were designed.

(2) In order to avoid dilution and diffusion of malodorous gases, the amount of collection should be reduced to a minimum.

(3) according to different deodorization phenomenon, respectively selected collection.

(4) According to the length of the pipeline and the degree of airtightness, refer to the "Heating Ventilation and Air Conditioning Design Code" (GBJ19-1987), calculate the residual air volume of the ventilation pipeline according to 10% of the system air volume.

2.3 air volume calculation:

Usually Q = V x ventilation coefficient, ventilation coefficient according to the odor concentration and personnel access to determine the general value range of 3~5 times/h;V refers to the volume of waste gas space. The total displacement is the sum of the total displacement of each unit.

2.4 fan selection:

The fan shall be a rear fan. After the open structure is covered and sealed, under the suction of the rear ventilator, a certain degree of micro-negative pressure is formed on the upper part of the sewage liquid level. Due to the effect of internal and external pressure difference, malodorous gas enters the gas collecting hood from the gap and cannot overflow. Thus, the use of rear fan effect is better.