Research On The Denitrification Capability Of Crossflow Membrane Bioreactor In Treating Caprolactam Wastewater

To advance a small step in resolving the difficulty of denitrification of high nitrogen strength wastewater, the wastewater produced during the caprolactam manufacturing was selected in this research as the water to be treated. This research adopted external inorganic ceramic membrane coupled anoxic/oxic bioreactor as the experimental system to treat the simulated wastewater, and examined its capability of denitrification and organic removal and the profile of its flux decline process. The research also fixed on the optimum running parameters and membrane operational conditions at a certain range.Before the running of the MBR, kaolin micro-particles with a mean diameter of 2μm were membraned on the inner wall of the ceramic membrane tube as the dynamic membraneto filtrate the simulated caprolactam wastewater. Results indicate that removal rate is higher and flux decline becomes much slower than filtrating directly with ceramic membranes. Through operating at low pressures, good performance provides warranty for MBR to reduce energy consumption.The research analyzed the transformation of nitrogen in the system and found that the nitrogen in membrane permeate was mainly nitrate. This phenomenon demonstrated that the limiting factor for the denitrification of the system was the anoxic segment due to the impropriety of the C/N ratio of the wastewater, for this inappropriateness resulted in the lacking of carbon source of the biological system. Through assaying the soluble microbial products (SMP) accumulated in the system, the researcher discovered that the SMP would be broken up from macromolecules to micromolecules and then be degraded. SMP could inhibit the activity of the microorganisms in the system, but the activity would recover after the microbes adapted to the environment.By adding powdered activated carbon (PAC) into the reactor to form biological activated carbon (BAC) system, the researcher compared the treatment efficiency and operation performance of it with the system without the addition of PAC.The results made clear that the addition of PAC could alleviate membrane fouling remarkably. However, the removal rate hasn't had any further significant improving due to the membrane's stable and outstanding cutting effects.The long-term operation of the system made sure that the high and stable removal efficiency is just reliable, and the dependable permeate water quality ensured that the treated water could be reused feasibly. The research evaluated the capital cost and treatment cost of- the MBR process. Contrasting the costs of MBR with these of conventional treatment process, the researcher found that there is great competition advantage in denitrification stability and reasonable potential in MBR technology.