How to treat aquaculture wastewater? (with technological process)

Chicken sewage treatment scheme

In the past 10 years, the "vegetable basket" project in the suburbs of our country has developed rapidly. Intensive and large-scale livestock and poultry industry is rising rapidly. At present, the total annual fecal output of live chickens and other poultry is as high as 580 million tons, and the total annual discharge of manure and water is as high as 6 billion tons. However, the amount of fecal water treated by engineering measures in the city accounts for only 25% of the discharge. Due to the lack of funds, most of these chicken farms are not perfect in the treatment and utilization of their manure, and the pollution to the surrounding environment is becoming more and more serious. Many chicken farms stink, mosquitoes and flies swarm, nitrate in groundwater seriously exceeds the standard, and infectious and parasitic diseases are prevalent in a few areas. Large-scale sewage has reached the point where it is necessary to treat it.

In the egg farm, chicken manure is mixed with leftover food, diet dripping water and manure tank flushing water to form a mixture of chicken manure. The chicken house is often washed, and the hatchery is regularly washed and disinfected, resulting in a large amount of waste water. Chicken manure wastewater not only contains high concentration of organic pollutants and solid suspended matter, but also rich in nitrogen, phosphorus and other nutrient elements, high content of ammonia nitrogen, which brings great difficulties to the biochemical treatment of chicken manure wastewater, especially the denitrification treatment.

Farm faeces and other pollution without treatment, along with discharge or improper disposal, pollute the ground, soil and groundwater. The pollution of fecal sewage to water and soil is mainly caused by organic pollutants and nutrients such as nitrogen and phosphorus.

1. Organic pollutants

Feces contain a large number of carbon compounds, ammonia compounds and other corrupt organic compounds, after entering the water, the water quality is turbid, the water color turns yellow and the smell becomes smelly. Under the action of microorganisms, when a large amount of dissolved oxygen in the water is consumed, the dissolved oxygen is exhausted, the organic matter is anaerobic decomposed, producing a variety of malodorous substances, the water becomes black and smelly, and the water quality deteriorates, making it undrinkable.

2. Nitrogen and phosphorus nutrient pollution

Nitrogen and phosphorus are the main nutrient pollutants in chicken excreta. In the process of organic decomposition, organic nitrogen and phosphorus are also mineralized into inorganic nitrogen and phosphorus. Most nitrides are oxidized to nitrates, some of which remain in the topsoil layer, while the other part seeps into the ground, which over time pollutes the underground water source. The sewage containing too much phosphorus flows into river ditches and ponds, which makes the water eutrophication, which can make algae and other plankton multiply and grow wildly, resulting in a decrease in the content of dissolved oxygen in the water and the production of a variety of toxins, which directly affect the growth of fish. Due to the proliferation of algae, the turbidity of water is increased, which hinders the photosynthesis of aquatic plants and algae and dies, and the dead algae and aquatic plants decompose under anaerobic conditions, resulting in the deterioration of the water body, thus harming the ecological environment.

3. Mineral element pollution

In the livestock and poultry breeding industry, in order to enhance the appetite of livestock and poultry, salt is often added to the feed, which leads to the increase of salt content in feces and urine, which directly affects the health of animals and the edible safety of animal products, pollutes the soil, and is disadvantageous to the growth of crops. The implementation of the project will help to improve the pollution of soil and water caused by livestock and poultry manure.

Chicken dung contains a high amount of sand, especially chicken dung. 8% of the gravel and shells are added to the feed, which are brought into the feces through the digestive tract. And there are more chicken feathers in chicken manure, especially in the moulting period.

Since the Ninth five-year Plan, China has done a lot of research and exploration on the treatment technology and technology of fecal sewage, carried out various experiments and practices on fecal sewage treatment, and achieved effective successful experience. The treatment process based on biochemistry and the combination of biochemistry and physicochemistry has been gradually formed. There are various processes commonly used in biochemical process, such as activated sludge process, biofilm process, combination of anaerobic and aerobic process, combination of hydrolytic acidification and aerobic process and so on. The engineering practice has proved that the aerobic treatment of fecal sewage from large and medium-sized chicken farms after solid-liquid separation is feasible and efficient, and it is more suitable for small-scale ones to combine hydrolytic acidification with aerobic treatment. The use of anaerobic digestion, on the one hand, can reduce energy consumption and operating costs, on the other hand, it can also recover methane gas and use it, so as to achieve the role of waste utilization.