Waste water treatment by flotation tank

By flotation tank technology, paper production and recycling villages can reduce 70-80% of waste water, recover up to 75% of pulp in the production process. This is a new technological solution successfully researched and applied by the Institute of Environmental Science and Technology (Hanoi University of Technology), opening up the prospect of treating environmental pollution in Vietnamese paper recycling villages. .

At present, there are about 1,450 villages in the whole country, but the Red River Delta region is most concentrated with about 800 villages, of which Ha Tay, Thai Binh, Bac Ninh, Hai Duong, Nam Dinh and Thanh Hoa are localities with secrets. The highest village level. With GDP growth rate of 8%, craft villages are considered to have the most powerful impact on changing the life and face of many rural areas, bringing many economic benefits and the main source of income for many households. family.

However, with the characteristic of fragmented production, handicraft, small households, craft villages are becoming a burden on the environment with the localities with many craft villages developing. Food processing, recycling, textile and dyeing are considered as one of the villages with the highest level of environmental pollution.

(Photo: Nhandan) According to Assoc. Dang Kim Chi - Institute of Environmental Science and Technology (Hanoi University of Technology), recycling village is a kind of craft village that can pollute all three components of air, water and soil environment . In paper recycling villages, the major pollution problem is solids such as fibers and pulp in waste water. For example, the recycling village of Phu Lam and Phong Khe (Bac Ninh) produces nearly 20,000 tons of products each year, discharging about 1,500 m3 of waste water to the environment every day. Waste water contains a large amount of toxic chemicals such as caustic soda, bleach, alum, resin and color . with BOD5 and COD content exceeding 4-6 times the permitted standard.

In the past, most of waste water from paper recycling villages was not treated and poured directly into the canals, ponds and lakes in the residential area and integrated into the general drainage system, causing environmental pollution. Only in the local and other regions and regions, now with the technology of floatation tanks, waste water will be collected, processed and reused. Waste water from craft villages is collected in ditches that lead to sand settling tanks and regulating tanks and then pumped to floating tanks. Here pulp (residual waste of the process) is separated by air bubbles supplied from the compressor. The pulp floating on the surface will be separated and returned to the pulp recovery tank and reused. The water after separating the powder will be transferred to another standing sedimentation tank to separate the remaining residue and discharge into biological lake by biological treatment. The treated waste water meets the waste standards and is ensured before being discharged into the receiving source.

Prof. Dr. Chi said: the most outstanding point when applying village wastewater treatment system, paper recycling industry by flotation tank will basically limit the problem of residual pulp in waste water . This is also the main factor that increases the level of water pollution. Because according to statistics, the two villages of Duong O and Phu Lam (Bac Ninh) produce about 1,500 to 3,000 kg of BOD and more than 3,000 kg of pulp into waste water every day. If collected, it not only reduces the level of environmental pollution but also collects it for recycling and reuse. Pulp obtained from this stage can continue to be used to produce low quality paper.

Environmental pollution in craft villages in Vietnam is becoming a pressing issue in most localities and is a difficult and difficult problem for environmental protection agencies. Flotation tank technology is considered a solution to solve environmental pollution problems with paper recycling villages. Simple construction works so the investment and operation costs are low with a capacity of 25-30 m ³ / h. In particular, the technology transfer price under the package method is only about VND 100 - 110 million, so it can be applied to establishments producing about 4.2 tons of paper / day. In addition, the system is also applicable to small to large paper production facilities.

However, in order to expand the application for the production villages, many opinions suggest that the most important issue is the consciousness of the manufacturer while there is no legal regulation to handle the environment. Vietnamese craft villages.