Treatment of pulping middle stage wastewater by th

2022-08-21
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Hydrolytic acidification activated sludge process for the treatment of pulping intermediate wastewater (Part 1)

Abstract: This paper studies the laboratory treatment of pulping intermediate wastewater from reed sulfate bleaching pulp factory with high pollution load, focusing on the treatment parameters and treatment results of hydrolytic acidification and activated sludge process

key words: pulping middle stage wastewater; Anaerobic; Hydrolytic acidification; Activated sludge method

what is the specific standard for the removal of intermediate wastewater by single-stage aerobic treatment? Take the spring change experimental machine as an example: the effect of BOD in is good, but its COD removal rate is low. Therefore, it is often difficult to make the effluent quality meet the national discharge standard to treat the pulping middle stage wastewater with a large pollution load by using a single-stage activated sludge process. This study attempts to explore the scientific and technological talents measured in our country, and a better treatment method to treat the pulping intermediate wastewater with high concentration and make it meet the discharge standard.

1 wastewater and test device

1.1 wastewater

the wastewater used for the test is from Hunan Yuanjiang paper mill. The plant uses Dongting Lake reed as raw material to produce cultural paper with self-made bleached kraft reed pulp. The pulping system uses a four stage vacuum washer to wash and extract black liquor in countercurrent. The black liquor is sent to the alkali recovery workshop, and the pulp uses CEH three-stage bleaching. The middle stage wastewater consists of cooking and evaporation wastewater condensate, pulp concentration wastewater after screening and purification, and bleaching wastewater. The nature of the wastewater is:

CODcr 760 ~ 1420mg/L

BOD5 220 ~ 415mg/L

SS 170 ~ 315mg/L

VFA 45 ~ 82mg/L

pH 8 ~ 9

1.2 treatment process and device

because the pollution load of the middle stage wastewater of pulping is high,the, Moreover, macromolecular substances such as lignin and carbohydrate are difficult to be degraded by aerobic microorganisms. Single stage activated sludge treatment can only reduce its CODcr value by 40% - 60% [1] [2]. In this process, a baffled anaerobic reactor is designed to hydrolyze the wastewater in the middle stage of pulping first, so as to degrade the macromolecular pollutants such as lignin and carbohydrates with impurities and foreign matters in E and oil delivery valve, and then treat them with activated sludge method. The laboratory treatment process and device are shown in figure 1. In the process, 4, 5 and 6 are made of Plexiglas and marked with scales

Figure 1 laboratory treatment process and device of pulping middle section wastewater

1-wastewater storage tank (effective volume 20L) 2-peristaltic pump 3-flowmeter 4-baffled anaerobic reactor (effective volume 12L) 5-aerated oxidation tank (effective volume 30L) 6-sedimentation tank (effective volume 15L)

1.3 test control conditions

temperature: the test device is installed in the air-conditioning room, and the reaction temperature is regulated by the air conditioner as required

ph value: adjust the pH value to 7.0 with hydrochloric acid before the wastewater in the middle stage of pulping enters the storage tank

nutrients: add urea and sodium trimetaphosphate in the middle water storage tank according to BOD ∶ n ∶ P = 100 ∶ 5 ∶ 1

others: before entering the storage tank, the waste water is filtered through a 200 mesh sieve, and the temperature is adjusted to the control temperature

1.4 analysis method

according to the method of reference [3] [4]

2 results and discussion

2.1 startup of anaerobic reactor and selection of hydrolysis and acidification parameters

the seed sludge of anaerobic reactor is from the digested sludge of Changsha No.2 sewage treatment plant, and the amount of inoculated sludge is 10gvss/l, plus a certain amount of fermented feces. At the initial stage of reactor startup, dilute the wastewater by one time, and feed water intermittently. The plastic extruder Market in China is full of confidence for 2h every day. After 15 days, feed water continuously, and the wastewater flow is 2l/h. After 30 days, feed water directly without dilution. At the initial stage of operation, the sludge is suspended in the reactor, and then the sludge gradually settles to the bottom in flocs to form a sludge layer. After 40 days, each chamber of the reactor formed a stable sludge bed. When the influent CODcr was about 1000mg/l, the effluent CODcr was stable at about 700mg/l, and the removal rates of CODcr and BOD5 were stable at about 30% and 18% respectively, indicating that the anaerobic reactor has begun to enter the stable operation stage at this time. (to be continued)

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