Air flotation-biochemical treatment of high concentration printing ink wastewater (2)

2.3.3 Biochemical system

Class A and Class B aerobic treatment pools are the core part of the whole system. Their main function is to use aerobic microorganisms to quickly absorb pollutants in sewage, and microorganisms use pollutants as nutrients to decompose and digest pollutants in the metabolic process. So that the sewage is purified. A segment effective volume 21m3, residence time 2.8h, gas to water ratio of 15:1, with a combination of semi-soft packing; B effective volume of 25m3, residence time 3.3h, gas to water ratio of 15:1, with porous filler. The two-stage aerobic treatment tanks were respectively equipped with water distribution pipe networks, aeration pipe networks, and mud drainage pipe networks.

2.3.4 Operation Effect

The results of the processing system operations are listed in the second schedule.
Attached Table II: Operational Effect Monitoring Time of Wastewater Treatment Facilities
June 2000 Ph 7.52 to 7.56 6 to 9
Mg/L SS 32~34 76%~99% 70
Mg/L CODcr 15.5 to 67.0 98% to 99% 80
Mg/L BOD5 6.67 to 27.1 98% to 99% 30
Mg/L Oil <5.0 95%～97% 5.00
Mg/L NH3-N 0.1~0.2 99% 10
Double Color 10 10
According to the results of the Second Schedule, the indicators of drainage after treatment all met the first level standard of the Guangzhou Municipal Wastewater Discharge Standard (DB4437-90). The design and operation of the entire project have met the design requirements.

3 Engineering Operation and Experience

3.1 Air floatation - biochemical process is reasonable and practical

In view of the fact that the company's printing ink waste water is characterized by low water content, high concentration, and complex composition, it is pretreated by air floatation to achieve solid-liquid separation. Since the company still has a certain amount of domestic sewage, ink waste water has a sufficient amount of domestic sewage to be comprehensively treated, so the flotation-biochemical method is used. The pretreated ink waste water is subjected to biological contact oxidation treatment together with domestic sewage. The results of the operation show that such a process is successful and the total processing efficiency is high. The air-flotation pretreatment had a 47.6% removal rate of printing ink wastewater CODcr, which greatly reduced the load of the subsequent biochemical treatment system, and provided favorable conditions for the final drainage compliance.

3.2 The use of air floatation devices and the selection of pharmaceuticals

The flotation device has less volume and floor space, and the structure of the cell body is simple. It can be started or stopped at any time, without affecting the quality of the effluent, and the management is convenient.

In the selection of flocculants, because the raw water contains multiple types of pigments, we use a variety of flocculants in combination. According to the test data, we used basic aluminum chloride and caustic soda as flocculants and coagulants. As the printing ink sewage is high turbidity water, we also added a small amount of high-molecular flocculant polyacrylamide as a coagulant. satisfaction. However, the cost of drugs is quite large. Under the premise of guaranteeing the effect of effluent, we have chosen ferrous sulfate instead of basic aluminum chloride. The effluent still meets the standards and the cost of drugs is greatly reduced. Several coagulants are added at the same time, so better results can be obtained, mainly because each coagulant has its own chemical group. Because of the different chemical groups, it can act as a bridging function in the water, giving full play to their respective advantages. Make the silk flower increase, the effect is obvious.

3.3 two-stage aerobic biochemical treatment process stability

Due to the biodegradability of the canteen sewage and domestic sewage, we use a two-stage biological contact oxidation tank to treat the integrated wastewater. The aeration branch pipe under the biochemical pool adopts the ABS perforated pipe. Although the one-time investment is large, the operation cost is low, the corrosion is not rusted, and the management is convenient. In the biological contact oxidation tank, a semi-soft composite filler and a porous filler are used, and biofilms on the bio-contact oxidation adsorb the pollutants in the sewage. The microorganisms complete the digestion and decomposition of organic matters in the metabolism, so that the sewage is purified. Wastewater and air enter the packing evenly from the bottom of the tank, which is beneficial to the oxidation and decomposition of organic matters in the waste water. The treatment effect is good.

From the regulating tank to the sand filter, we have integrated one buried in the ground to save floor space, and the ground can be restored to flat driving.

3.4 Influence of Influent Concentration on Treatment Effect

The project was commissioned in December 1999. The concentration of CODcr in the influent printing wastewater ranges from 1380 to 18200 mg/l, and the BOD5 concentration ranges from 544 to 7600 mg/l. The water quality changes greatly. After the sewage treatment system, the effluent can still meet the emission standards. It can be seen that the process device can withstand higher pollutant loads, resist impact, and efficiently treat high-concentration wastewater.

4 Conclusion

The ink waste water often contains many different types of pigments. The components are complex, and the COD concentration is high. It is difficult to degrade. If relying solely on physical or biochemical treatment, or increasing flocculation and biochemical reaction time, the sewage treatment project will occupy a large area, and the process Long, high engineering costs, and unsatisfactory treatment results, the study of unit combinations should be strengthened. In this case, since the amount of ink waste water is small, if it is treated separately, the process flow will be long, the investment cost for the ton water project will be high, and the management will be complicated. Now there is a certain amount of domestic sewage in the enterprise, and the flotation-biochemical process is used. Operation practice shows that the process has stable effects, impact resistance, small footprint, low consumption and high efficiency, convenient management, and simple maintenance. It is a reasonable and effective solution to deal with the typical wastewater production wastewater.