How to choose the diameter of small sewage treatment facilities and sewage pipe network in rural areas?

Generally speaking, I don't support rural sewage access to the main network.

According to the amount of sewage, determine whether to access the municipal large pipe network. We know that the cost of connecting scattered point source sewage into the pipe network is very high. Of course, you can calculate the sewage pipe network according to the method of municipal sewage pipe network, but you should know that the construction of the pipe network is very troublesome and expensive, which may not be cost-effective. Studies have shown that it is worthwhile to collect rural sewage from more than 100 households within 5 kilometers, and it is more cost-effective to connect the sewage to the sewage main pipe network. If it cannot be achieved, it will be decentralized on the spot. -This reference data is the conclusion reached by an American scholar at the seminar on sewage in small and medium-sized towns and rural areas held in Beijing International Convention Center on October 20/1.

I am a water treatment worker. I have done about a dozen projects in rural areas below 100 tons/day. You don't seem to be very large. If a sewage treatment station is built in rural Beijing, the investment should be between 300,000 and 500,000 according to the market price of 20 12. The cost per ton of water treatment, including labor and excluding depreciation, should be 2~4 yuan/ton, but excluding labor, it is about 1 yuan/ton.

So I suggest you compare it first, and see if it is more cost-effective to deal with it in a decentralized way. Because I have done a lot in Beijing, because it is really not cost-effective to do pipe network engineering, and decentralized sewage treatment stations are used for decentralized treatment. For example, in a village I built in 2009, I would rather spend 680,000 yuan to build a 50-ton/day sewage treatment station than spend a pumping station to lift the sewage to a pipe network 5 kilometers away, because there are a series of problems such as deep burial, high cost, management trouble in upgrading the pumping station, and difficulty in land acquisition.

Characteristics of rural sewage:

1. There is water during the day, concentrated in the morning and evening, and almost no water flows out at night. The coefficient of variation is very large, and 10 is not too much.

2. In winter, the amount of sewage in northern rural areas is actually very large, but the water quality is very clear and easy to handle. Mainly, many rural villagers who use water without spending money are worried that the pipeline will be blocked in winter, so they leave the water pipe on all day. At least there are villagers like Beijing, so please check the winter living habits of the village before making the design. -Why? For example, in a village in Fangshan District, Beijing, water is used for free. The daily sewage in summer is only 30 tons/day, but it is as high as 120 tons/day in winter. Therefore, the so-called pipeline calculation theory is completely ineffective. -This is the real version of rural sewage in China. So, if you dare to build a village official website, I suggest that it is best to investigate whether the water consumption in this village costs money.

3. The management level of rural pipe network facilities and sewage treatment facilities is very weak, and many of them are managed by illiterate old people, so you should consider the level of your future maintenance and management workers. It's not that people are lazy, it's true that no one can get these jobs, and there are fewer and fewer strong laborers in rural areas, so there are more jobs. In particular, the management technology of sewage treatment stations is even weaker. The existing sewage treatment stations are all fancy and not suitable for rural areas, so many of them cannot be displayed. So, you should pay attention to this. If you need to be a sewage treatment station when designing your own pipe network, please leave all the excess pipes to the sewage treatment station. You must pay attention to this. Off topic, I hope other netizens who can see this answer can pay attention to it. To be a decentralized sewage treatment station in rural areas, it is best not to choose activated sludge process, especially complex technologies like AO and MBR. The quantity and quality of water vary greatly, the management quality is low, the village is poor, and the depreciation is too high to use. Really can't. It is also faced with the situation that every village has to face power failure in turn every month, and the activated sludge method cannot be used normally. Land treatment technologies (artificial rapid infiltration, constructed wetland, biological sand filter) must be used, because there is no shortage of land in rural areas, but funds and technical support are lacking. In the past five years, most of the three or four hundred rural sewage treatment stations in Beijing, which are relatively small and basically adopt traditional technologies, have completed their work. What a profound lesson.

Get to the point, you have to do some personal experience in pipe network and rural pipe network:

No large-scale municipal pipe network design has been done, but there are many rural sewage treatment facilities, and the water volume of the pipe network still has a say. I'll give you some advice on pipe network calculation, which is worth your consideration:

1) septic tanks are generally not used for rural sewage, unless it is a newly relocated immigrant village (the government pays for the building). In rural areas, people usually build their own houses, and no one builds septic tanks, let alone official website. In fact, rural sewage actually flows directly to the road along the yard. Beijing has the habit of washing face and vegetables, especially in summer.

2) There is a lot of sewage and garbage in the countryside, which you can't imagine. Because there is no septic tank and good garbage collection habits, a lot of garbage, large and small, has been found in many new rural sewage facilities. Therefore, your pipeline should be designed as a concrete pipeline with a minimum of d300.

3) Rainwater problem in rural areas is very troublesome. In 2004, I made a calculation of river rainfall in some villages in Shenzhen. I feel that the average village in the countryside is very big and wide. Therefore, it is unrealistic to collect rainwater. In fact, it is better not to collect rainwater. People's villages are basically water permeable, so it is really enough to do a good job of open channel drainage. I don't think you need to make too much trouble in this matter. Rainwater from rural areas directly flows into rivers in the fields, especially in rural areas where agriculture is dominant. The villagers hope that all the rainwater will flow into the fields. Moreover, many old villages are drained by open ditches. Because of the large flow and simple management, it is best not to make rainwater pipes like cities. Because it is inevitable that rural garbage is littered everywhere, don't expect how much your rain screen can block (because everything made of metal is in danger of being stolen in China). Once it rains, it will be very troublesome for the village to rush into the rainwater pipe network. It is suggested to make an open ditch, which is really practical in rural areas. If we have to do rainwater drainage in pipe network, regardless of investment and management, we must outline the catchment area of all river basins with topographic lines, and then choose a standard that comes once every n years, such as the rainfall statistics of the previous 1~2 hours (it is best to find a "typical rain" from meteorological data, which will definitely be asked by you at the expert review meeting), and then determine a precipitation and maximum water quantity, and then multiply it by a runoff coefficient according to the specification. But in principle, no matter how small it is, it can't be less than 500mm, otherwise the unorganized garbage in the countryside will block your heart when it rains.

You are still asking about the length of the pipe network. I can't tell you the length. You can only measure yourself against the drawings. It would be most convenient if the sewage can be lifted to the main network, but the information I know is that the rural areas near the town are basically done at present, and the rest are relatively remote.

Finally, I remind you, don't make the sewage in rural areas the same as that in cities, or you will be in big trouble. The characteristics of rural areas are very prominent, and the design concept of water quantity and quality pipelines is completely different from that of cities. If you copy the norms, you will suffer. Of course, if you meet experts in rural sewage pipe network, you may not necessarily agree to copy the specifications. The current rural "norms" are completely blank, because the personality of each village is too distinct, and there is no way to formulate a norm from village to village. I can only give you some experience here, so you can study it yourself and think it over before making a decision.