Development of waste collection and water treatment system of cage culture in open waters

Abstract: At present, tail water generated by the cage culture contains a large quantity of residual feed, feces and other solid waste. If completely discharged, it will cause serious water eutrophication and severe damage for the ecological environment of culture waters. In view of the above question, the waste collection and waste treatment system of cage culture in open waters was developed for the cage culture reducing the tail water discharge and pollution into waters. This system is composed of the waste collecting device for collecting feed bait and fish feces, water supply and drainage system for water circulation into the closable cage, waste collection system for the scale of the cages and closable cages, filter for filtration to feed bait and fish feces and tail water processing system devices five parts. Compared with traditional net cage culture on water pollution, the waste collection and water treatment system of cage culture has four improvements: 1) Adding a dirt collecting bucket in each cage at the bottom, the solid waste together into the bucket, to facilitate the rapid promotion of waste collection. 2) In view of the traditional net cage waste collection, design sewage collection central gathering side lifting bucket apparatus; For a closable cage except with waste collection function, also has a deep water net cage will ascend to, bottom discharge function, with supreme and carry out the way water exchange, pneumatic recoil function, prevent the filter mesh is waste particles blocking. Water door with one-way flow function, prevent the back flow of sewage. 3) For solid waste water after filtration, using an ecological floating bed water pot of economic plants (such as Canna indica L., Acorus calamus L.) and microbial biofilm formation methods, nutrient rich water to fully absorb the water reach the discharge requirements. 4) The whole system adopts compressed air as the power source, centralized collection by using the method of pneumatic lifting implementation of waste water, centralized pneumatic depths can be a closed cage of ascension, as well as an aerated ecological floating bed. Waste collection in the running process of the system, collecting cage precipitation of tail water lifting and the air consumption, pressure has a very close relationship. The system of the waste collection tube with an inner diameter of PVC steel wire spiral reinforced hose 80 mm. 4.5 m under the water and gas water mixing chamber, namely air injection depth of 4.5 m. Through the test, in improving the sludge hopper in tail water, can be found through observation proposed by turbidity of tail water gradually becomes transparent, in this process, the 18 dirt collecting bucket of water statistics, the average sewage collection bucket lifting water is 0.34 m3. The results elaborated through professional transformation of large water cage facilities, constructed from the waste collection, solid-liquid separation, and the breeding of tail water after separation by ecological floating bed hanging membrane technology to physics and a set of ecological treatment system. The system collects the water discharged after treatment, the total phosphorus (TP), ammonia nitrogen (NH3-N), chemical oxygen demand (COD) were 0.305, 0.095, 16.2 mg/L, reached a 'freshwater ponds water discharge requirements of ST9101-2007' II class standard. On the ammonia nitrogen and other indicators, the system realizes the standard exhaust culture of the tail water, greatly reducing the concentration of cage aquaculture wastewater to the water discharge.