[Determination of kinetic parameters of activated sludge in an MBR wastewater treatment plant].

One of the main problems in application of MBR technology is lack of reliable kinetic parameters for process design. The activated sludge in the aerobic tank of an MBR municipal wastewater treatment plant was investigated therefore. Using oxygen utilization rate method, following kinetic parameters were measured: heterotrophic yield coefficient YH = 0.693, autotrophic yield coefficient Y(A) = 0.263, heterotrophic decay coefficient KdH, = 0.108 d(-1), autotrophic yield coefficient KdA = 0.089 d(-1), specific maximum COD removal rate v(mS), = 1.94 mg x (mg x d)(-1), half saturation constant for COD removal K(S) = 34.6 mg x L(-1), specific maximum ammonia removal rate vmN = 0.18 mg x (mg x d)(-1), half saturation constant for ammonia removal K(N) = 1.06 mg x L(-1). Compared with the normal reported data of conventional activated sludge process (CAS), Y(H), KdH obtained are higher and vmS, vmN are lower. The high sludge concentration condition of MBR process may account for those differences.

[Effect of ozone on membrane fouling in water and wastewater treatment: a research review].

As a high efficient water and wastewater treatment technology, membrane filtration has been mainly used in wastewater treatment as membrane bioreactor, in reclaiming secondary effluent,treating surface water and potable water, and etc. Membrane fouling is a main obstacle to the wide application of membrane technology. Ozone has strong oxidizing power and has been utilized widely in water and wastewater treatment. In recent years, researches on combined process of ozone-membrane filtration are increasing. This paper does reviews and analysis of these researches. It is noticed that there has been a few of researches on the ozone treatment plus MBR process. Pre-ozonation of feed to MBR and slight ozonation of the mixed liquid in MBR may be used to relieve membrane fouling.Combined processes of ozone-membrane filtration can be divided into three classes in terms of the function of ozone and the system configuration: (1) cleaning the fouled membrane with ozone; (2) separate ozone-membrane filtration process; (3) integrated ozone-membrane filtration process. Although most reports supported that ozonation can control membrane fouling development,there were contrary results. At present, researches on the mechanisms of ozone's effect on membrane fouling control concentrated on the change of organic composition of the filtration influent under ozonation, however, particulate substances, microbial and inorganic substances may also be affected and then play roles in membrane fouling, depending on source water quality and process configuration. Moreover, there have not been common parameters to evaluate the ozone diffusion equipment and efficiency. The authors suggest that further researches should emphasize on integrated ozone-membrane process, and more attention should be paid to the cost-effectiveness of the combined process.

[Production of ligninolytic enzymes in bioreactor].

Production of ligninolytic enzymes under nitrogen limited conditions(C/N = 56/2.2) was studied in a 5-L stirred tank bioreactor with a working volume of 2 L for obtaining higher production of ligninolytic enzymes by white rot fungus Phanerochaete chrysosporium BKM-F-1767 and its control strategy. Results show that the manganese peroxidase (MnP) and laccase (Lac) reached peak at the sixth day and the seventh day, respectively, and the variation of them with time in a batch cultivation are similar to the results by agitated Erlenmeyer flasks; however higher enzyme activity was not achieved by applying a fed-batch strategy, in which nitrogen limited medium was fed to the reactor. In addition, variation of pH during cultivation was related to the growth of P. chrysosporium and enzymes production during both batch and fed-batch cultivation. The pH value of liquid medium began to decline when the enzyme activity occurred in the system, and the decline became more and more slow along with the decrease of enzyme activity at the end of fermentation. So, pH would be as a control parameter to find out the growth of P. chrysosporium and enzymes production during incubating P. chrysosporium. However, fed-batch strategy still need further study.

[Resistance analyses for recirculated membrane bioreactor].

The resistance analyses for recirculated membrane bioreactor by the resistance-in-series model and the modified gel-polarization model respectively were extended to the turbulent ultrafiltration system. The experiments are carried out by dye wastewater in a tubular membrane module, it is found that the permeate fluxes are predicted very well by these models for turbinate systems. And the resistance caused by the concentration polarization is studied; the gel layer resistance is the most important of all the resistances.