Since the publication of the Ten Rules of Water, there have been waves of pollution control in black and odorous water all over the country. According to the data provided by the National Information Platform for Urban Black-odorous Water Treatment of the Ministry of Housing and Construction, 1745 of the 2100 identified black-odorous water bodies have been treated and certified, 264 of them have started construction, and 91 of them are in the process of formulating treatment plans. Overall, the completion rate of treatment reached 83%, and remarkable achievements were made in the treatment of black and odorous water bodies.

• Data Source: National Information Platform for Urban Black and Stinky Water Treatment of the Ministry of Housing and Construction

The total length of 2100 black and odorous water bodies was 7938.88 kilometers, with a total area of 1462.79 square kilometers. Up to now, China has completed the regulation of water body 6727.54 kilometers, an area of 1211.34 square kilometers, the completion rate is 84.74% and 87.45%, respectively.

• Data Source: National Information Platform for Urban Black and Stinky Water Treatment of the Ministry of Housing and Construction

The treatment of black and odorous water is a systematic project, including sewage interception, silt removal, ecological restoration and so on. And in almost most of the treatment projects of black and odorous water body, there is a group of vocabulary that appears quite frequently - dredging.

Cleaning up silt means cleaning up the silt at the bottom of the river. The river bottom silt contains a large number of pollutants which have been deposited by various kinds of sewage for many years. If it is not effectively treated, even if other measures come into effect, the river water quality will be improved, and the pollutants in the bottom silt will enter into the water body, which will deteriorate the water quality. At present, dredging and dredging are the most important means to control the source pollution of black and odorous water and to treat the river bottom sludge.

Thirty-three

Sludge dewatering can effectively save freight and facilitate subsequent treatment in silt removal projects.

If the sediment is not properly treated, the treatment effect of black and odorous water will be greatly reduced, even repeated. From May to July this year, nearly 60% of the 993 black and odorous water bodies inspected by the national special supervision involved in sediment treatment. Many water bodies lacked pollution investigation and assessment before silting removal, and the situation of sediment random stacking occurred from time to time. According to a regular conference held by the Ministry of Ecology and Environment in July this year, 76 sediments from black and odorous water bodies were randomly stacked, which could easily cause secondary pollution.

At present, there are three main treatment methods for these river bottom sludge: sanitary landfill, incineration and resource utilization. Whichever way of treatment, it needs to be dehydrated. The reason is very simple, these treatment facilities will not be built on the edge of the river construction site, many facilities geology is far away from the river construction site. At the same distance, the weight directly determines the transportation cost, and the reduction of the weight means the reduction of the cost.

There are two main methods of sediment removal: hydraulic and mechanical. The water content of the sediment is above 80%. At present, many dewatering equipment can reduce water content to 35%-40%. That is to say, the weight of sediment can be reduced by 40%-45%. On the premise that the transportation cost per unit distance remains unchanged, the total transportation cost can be reduced by more than 40%.

In addition, sludge dewatering treatment can effectively reduce the re-inflow of sewage into the river, improve the site environment and reduce secondary pollution. Therefore, it is necessary to equip dewatering equipment on the site of silt removal.