The Biochemical Denitrification Pilot Experiments Research On Acrylic Fiber Wastewater By High Efficient Bacteria

Acrylic fiber wastewater is mainly wastewater containing cyanide in the production process of acrylic fiber. This kind of wastewater is complex with a high CODCr, ammonia nitrogen and low B/C. Wastewater contains a large number of difficult biodegradable, toxic substances, which inhibit the growth and metabolism of microorganisms. Therefore, acrylic fiber wastewater meets the emission standard, which is a difficult problem in industrial water treatment research for a long time.This pilot study was conducted in a wastewater field in Jilin Qifeng chemical fiber corporation. The paper studies on acrylic fiber wastewater further removal of nitrogen, mainly research object being the moving bed biofilm reactor(MBBR). The degradation treatment effects on CODCr and ammonia nitrogen of acrylic fiber wastewater are researched in the ordinary MBBR and the addition of high efficiency bacteria MBBR, respectively. Under the two test experimental conditions, there come some conclusions as follows:(1) In order to decrease the effluent CODCr of the acrylic fiber wastewater to discharge standard(160mg/L) after biochemical and ordinary MBBR systems processing, the influent CODCr was controlled in 500~600mg/L.However, under stable operation, the ordinary MBBR effluent CODCr value maintained at 200mg/L and NH4+-N value had a small amplitude degradation by controlling the corresponding operation parameters: adding alkalinity 0.4g/L,adding phosphorus source 2mg/L, dissolved oxygen in 5~6mg/L and 100% reflux ratio.(2) The CODCr of the acrylic fiber wastewater decreased to a certain range after diluted.Through trial biodegradation of ordinary MBBR, the effluent CODCr dropped to a certain value and can not be further reduced. The reason is that there exist a certain proportion of non biodegradable material in the acrylic fiber wastewater, so biochemical treatment ability is limited.(3) In order to keep high efficient bacteria sustaining efficient treatment effect on acrylic fiber wastewater in addition of high efficiency bacteria MBBR pilot scale experiments, the experiments conditions were strictly controlled as follows: temperature in 28~32 degrees,dissolved oxygen(DO) in about 5mg/L, adding phosphor source 2mg/L. The influent CODCr value is 700-900mg/L and NH4+-N value is 110-130mg/L in he whole process. The pilot MBBR took intermittent inflow of operation mode. In 5h, 6h, 8h stage, addition of high efficiency bacteria MBBR effluent CODCr value was stable at around 260mg/L, NH4+-N valuebeing lower than the 10mg/L, TN removal rate being about 35%. In 10 h stage, addition of high efficiency bacteria MBBR effluent CODCr value was about 260mg/L, NH4+-N value being maintained at about 30mg/L, TN removal rate being about 30%.(4) In the process of nitrification, alkalinity and temperature control are essential.Nitrification bacteria environment can maintain optimum metabolic activity in the pH value7.8~8.2.In order to avoid pH appearing large fluctuation in the environment around nitrification bacteria, the basicity was added. Also appropriate temperature(28~32 degrees) is in favor of nitrification. The temperature has direct effects on microbial enzyme system,which will slow down or even stop nitrification rate of biochemical system. The amount of sponge iron were added to reactor(MBR), which formed iron system through the automatic releasing. To a certain extent, the method had the removal effect on CODCr of acrylic fiber wastewater, but it needed long time to work and the degradation ability was limited.(5) During addition of high efficiency bacteria MBBR pilot scale experiments, some experience were summarized. These experience have certain guiding significance in the acrylic fiber wastewater field. ?1 The high efficiency bacteria have a good degradation ability.At the beginning of adding high efficiency bacteria, the effluent ammonia value is high,sometimes even higher than the influent ammonia value, which lasts a period of time.Once the high efficient bacteria adapting to wastewater, the reactor effluent ammonia value decreases rapidly and sometimes the effluent ammonia nitrogen value is blank. ?2 With the wastewater load increasing, nitrification activity is blocked in biochemical system. As a result,effluent ammonia value maintains high. Denitrification is promoted by adjusting dissolved oxygen concentration(DO) of different reaction zone in the reactor, which is advantageous to nitrification. Then the purpose of reducing effluent ammonia nitrogen is achieved. ?3 The carrier has a influence on biofilm formation in moving bed biofilm reactor(MBBR). The pilot experiment used polyurethane foam carrier, which is more significant. Due to the reactor have operated too long time and the internal aeration aged, the internal aeration was not balance in the reactor, which was extremely easy to produce local anaerobic zone. In addition, the carrier should keep in tumbling state during normal operation, otherwise the mud will produce between the carriers, resulting in anaerobic.