1 Urban pollution status quo
Because of industrial development and increasing population, Dandong City, industrial wastewater and domestic sewage is increasing, 80% of the volume of industrial wastewater is untreated, domestic sewage, in addition to some of the hospital sewage is treated, the rest of the whole untreated. Industrial wastewater and domestic sewage are discharged into the Yalu River, so that the middle and lower reaches of the Dandong section of the Yalu River is subject to relatively serious pollution. Dandong Water Company in February 2009 had a Yalu River Langtou to love the river water quality monitoring, to the four ditch water pollution is the heaviest, chloride up to 2,345.00mg / L, phenol up to 0.06mg / L, and there is a different smell and odor, has been unsuitable for drinking water as a source of life. Sidaogou water source, Jiangqiao water source has been changed to industrial water source. In addition, Dandong City and the Yalu River across the city of Xinyizhou financial difficulties, urban sewage treatment plants are delayed construction; due to the Yalu River is the border river, even after many efforts, Dandong City, the sewage treatment project can be started as soon as possible, the lower reaches of the Yalu River pollution problems in the near future is not likely to get a complete solution. In recent years, due to the decline in river levels, the Yalu River, a number of water sources have been affected by seawater back-up pollution.
2 Wastewater Treatment Measures
2.1 Production Wastewater
In the purification treatment of the water purification plant, the amount of water used in the water plant's filter pond rinsing accounts for about 2.0% of the water supply of the water purification plant, in order to realize the sustainable development of water resources, the two water purification plants of the project have adopted the recycling measures of production wastewater back to the distribution wells in order to reduce the amount of water loss. The project collects the backwash water from the filter tank by setting up a recycling basin, which, after a certain residence time, allows the larger particles contained in the wastewater to settle, such as the filter media that escaped from the backwash.
The important role of the recycling tank is to eliminate the filter tank intermittent backwash to the return flow of the pulse effect, reduce the disturbance of the distribution wells, and the backwash water contains particulate flocs retained in the filter media, this floc still has a certain adsorption capacity, will be returned to the front end of the water treatment can improve the flocculation of the raw water conditions, especially in the low-temperature and low turbidity period can play a role in enhancing the treatment effect, save flocculant injection It can improve the flocculation condition of raw water, especially in low temperature and low turbidity period, it can play the role of enhancing the treatment and saving the flocculant dosage.
2.2 Domestic Wastewater
Living wastewater in the plant area of Sidaogou Water Purification Plant will be discharged into the interceptor trunk pipe constructed before this project after simple treatment in septic tanks, and will be sent to the wastewater treatment plant downstream about 2.6km away to be treated together with other urban wastewater.
Toad Pond water purification plant is far away from the city, there is no intercepting trunk pipe nearby can be utilized, domestic sewage must be treated, the project selects the buried integrated sewage treatment system for treatment, after treatment, discharge to the nearby water bodies to meet the standards.
3 Sludge treatment measures
Because the Sandougou wastewater treatment plant is expected to be completed and open to water in early 2018, which is earlier than this project; and the wastewater treatment plant interceptor trunk pipeline from the side of the Sidougou water purification plant, and the Sidougou water purification plant is limited to the site, so the Sidougou water purification plant does not build the mud treatment system, the reaction tank, precipitation tank of the discharge of sludge water is directly discharged into the interceptor trunk pipeline to the downstream of the approximately 2.6km away to the wastewater treatment plant together with other urban wastewater.
The Toad Pond Water Purification Plant is far away from the city, and there is no intercepting trunk pipe nearby to be utilized, so it is necessary to build a mud treatment system to treat the mud discharged from the reaction tanks and sedimentation tanks.
In the process of water treatment, the water purification structures will be settled in a certain amount of sludge, and sewage treatment is different, these sludge generally does not contain toxic substances, the composition of the suspended solids in the raw water and floc produced by the injection of drugs is dominant. Because it does not contain toxic substances, the toxic effect on the environment is small, and the sludge treatment investment is high, therefore, in the past, the domestic water supply treatment of sludge is generally not treated, directly discharged. At present, with the improvement of environmental protection requirements, the disposal of this part of the sludge puts forward new requirements. Although the sludge produced by water supply treatment does not produce toxic effects on the environment, it will cause the turbidity of the receiving water body to increase, silt the riverbed and pollute the surrounding environment. Therefore, this project toadstool water purification plant sludge treatment system and water treatment system synchronization construction.
Currently, the main treatment process adopted by our country for water supply sludge is: collection→concentration→dehydration→exportation. Collect mainly for flocculation pool, sedimentation pool sludge, set up sludge pool; concentration can be used gravity concentration and mechanical concentration, due to the water purification plant sludge to the original water contained in the suspended matter is mainly different from the sewage treatment of biological sludge, easy to precipitate, so it is suitable for the use of gravity concentration mode of treatment; such as the use of mechanical concentration, will consume a lot of electricity, resulting in a waste of energy and an increase in operating costs. Dewatering is generally treated by mechanical dewatering, and the dewatered sludge is transported to landfill to realize the final disposal of sludge.
The proposed centrifugal dewatering machine for the mud system of the Toad Pond Water Purification Plant of this project is characterized by a simple process, convenient operation and control, and a high degree of automation; moreover, centrifugal dewatering machine consumes a small amount of medication; the shape of the machine is in the form of sealing, and the working environment of the dewatering room is relatively clean.
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