High concentration chemical wastewater treatment project example

High-concentration chemical wastewater treatment project example Yang Wandong Abstract Fe-C and catalytic oxidation pretreatment + A/O biochemical treatment process is used to treat a chemical plant wastewater in Lishui, Zhejiang.

The designed total treated water volume is 1500m3/d, of which the concentrated wastewater is 160m3/d. The designed influent water quality is: high-concentration organic wastewater COD 6~9, and the treated effluent can meet the standard emission.

The treatment of high-concentration chemical wastewater has always been a problem in the field of wastewater treatment. The main characteristics of this type of wastewater are high COD and poor biodegradability (generally BOD/CODC0.1), and the nature of wastewater varies greatly due to different types of industries and product categories. The enterprises that produce such wastewater are mostly pharmaceutical and chemical companies. As the pollution of this type of wastewater is very serious (many are toxic), the country has explicitly prohibited direct emissions. A chemical plant in Lishui, Zhejiang Province, produces pharmaceutical intermediates represented by thiophenol. In the production process, there are a number of high-concentration wastewaters and a large amount of flushing wastewater. If they are discharged without treatment, they will cause serious pollution to the surrounding water bodies.

1 Designed water quantity, water quality 500m3/d, including concentrated waste water 160m3/d, other wastewater (3) designed effluent quality. Implementation of the “Integrated Wastewater Discharge Standard” process flow According to the characteristics of the plant's wastewater, to achieve the first-class water discharge standard, it must be treated in a separate manner. That is, the concentrated wastewater is first subjected to physical and chemical pretreatment, and then it is treated together with other wastewater for biochemical treatment. The specific process flow is shown (dotted line indicates the physicochemical treatment process). The concentrated wastewater discharged from the workshop flows into the conditioning tank and then enters the Fe-C reaction tank. The galvanic reaction formed in Fe increases the pH of the wastewater, while the coagulation granules formed by Fe3+ in the reaction process of the micro-electrolysis wastewater treatment provide conditions for subsequent neutralization and plate-frame filtration. The water after the micro-electrolysis reaction is raised by the acid-resistant pump and enters the neutralization tank. In the neutralization tank, lime milk was added for neutralization, and the pH was adjusted to 9 to 10. During the neutralization process, aeration with air aeration was used. The neutralized wastewater is pumped into the plate and frame filter presses, and the filtered wastewater flows into the intermediate pool. The sludge formed by pressure filtration is transported to the brickwork of the Red Brick Factory. The waste water is filtered to remove most of the suspended particulate matter, so that the waste water is primary purified. The waste water flowing into the intermediate pool is pumped into the catalytic oxidation tower and the oxidant is introduced into the tower. The waste water is catalytically oxidized in the tower to remove some of the organics. The biodegradability of the waste water after catalytic oxidation is greatly enhanced, providing the necessary conditions for the further biochemical treatment of the waste water. Catalytic oxidation plant complete sets of equipment provided by Zhejiang University Environmental Engineering Corporation. The catalytic oxidation device is a patented technology oxidant using ClO2, the catalyst is heavy metal. The catalyst is attached to the carrier in the tower, and the wastewater is catalyzed and oxidized on the surface of the carrier by continuously introducing an oxidizing agent into the tower, so as to achieve the purpose of purifying the wastewater. The catalytic oxidation device has been successfully applied to the treatment of nearly ten chemical waste waters and has achieved good results.

After the above-mentioned physical and chemical pretreatment process, concentrated wastewater can not only (1) D removal rate of 60% ~ 70%, while BOD / COD from the original 0.015 to 0.15 or more, significantly improved the wastewater degradability. The materialized wastewater enters the water quality adjustment pool and is mixed with other wastewater from the inflow plant. The mixed waste water is pumped up into the A/0 biochemical tank. In the biochemical pool, the organic impurities in the water are removed by the action of aerobic and aerobic bacteria, so that the wastewater is further purified, then the mixed wastewater flows into the second settling tank, and the supernatant is discharged after the slurry is separated.

The sludge in the second settling tank is returned to the A section and 0 section of the A/O pool, and the remaining sludge is pumped into the neutralization tank along with the neutralized impurities of the concentrated waste water.

3 Main structures to be dealt with 3.1 Underlying structures The underground structures to be built include conditioning ponds, Fe pools and water quality adjustment pools. The total plane size is 10mX10m, the effective water depth is 28m, and the total depth is 3.3m. The reinforced concrete structure, the total residence time of the ground ultra-high pool is 16h, and the plane size is 4mX10m. Due to the lower pH of the raw water, the inner wall of the whole pool adopts cyanide anticorrosion. The pool is divided into 2 compartments, the front part is the water adjustment pool, and the rear part is added iron scraps and activated carbon as the micro-electrolysis reaction pool. In order to make the water quality uniform and complete, aeration (gas to water ratio 3:1) is performed in the micro-electrolytic cell. The Fe-C reaction tank works well and can raise the pH to about 4 to 5. In this project, coke is used as a substrate for a one-time dosage of about 0.8t, and the average daily dosage of iron filings is about 0.03t. () Intermediate pool. The middle pool is a temporary storage tank for press-filtered water. The effective residence time is 5h, and the plane size is 6mX2m. In order to prevent accidents from happening, the inner wall of the pool is also protected by cyanide.

(3) Water quality adjustment pool. The water quality adjustment pool is where other wastewater from the plant is mixed with the wastewater after catalytic oxidation. Plane size 6mX 8m, design effective residence time 22h. Due to the large factory area, there is a certain buffer time for other wastewater along the open channel collection process, so the water quality adjustment pool can fully meet the requirements of water quality adjustment.

3.2 Above-ground structures The above-ground structures that are built together include a neutralization tank, A/O pool, and secondary sedimentation tank.

(1) Neutralization pond. The main function of the neutralization tank is to adjust the pH of the water after microelectrolysis. The total residence time is 18h, the plane size is 4mX water depth is 4m, and the total depth is 5m in 2 grids alternately. The inner wall is cyanide and anticorrosion, and it is built together with the A/ 0 pool. The air is stirred in the standpipe, and most of the organics in the air-water ratio 61 are removed here. The design and oxygen A section adopts the time delay method to further improve the biodegradability of the wastewater, the residence time is 8 hours, the perforated pipe aeration mixing is set at the bottom of the tank, the activated sludge method is used for the aerobic 0 section, and the mixed solution sludge concentration is designed. 4gMLSS/L; sludge load 0.09kgBODAkgMLSS. 3.3 Auxiliary structures Affiliated structures include fan room, dehydration room, and catalytic oxidation equipment room and operation room, including a brick-concrete structure room with a plane size of 7.8mX8m, and a fiberglass shed of 8mX8m. .

4 The operating conditions of the yuan, after four months of debugging, the operation is basically stable, and the treatment effect has also reached the designed effluent water quality index (see Table 1).

Time influent effluent Influent effluent Concentrated effluent Other effluents Concentrated effluent Other effluent Due to the better treatment effect of this project, the effluent discharge problem of the plant is fundamentally solved, which not only protects the environment, but also lays the foundation for the further development of the enterprise.

Institute of Environmental Engineering, Zhejiang University Tel: (0571) 87,784,138 Revised: (1) 2 buckets 17