Tong Zhu

Treatment of domestic sewage by a metal membrane bioreactor

A submerged flat metal MBR (membrane bioreactor) was used to treat synthetic domestic sewage in this study. The experiment was continued for 270 days and ran under two modes as AMBR (aerobic membrane bioreactor) and A/O-MBR (anoxic/aerobic membrane bioreactor) at a permeate flux of 0.4-1 m³/(m² d). PVA (polyvinyl alcohol) gel beads were added to the aeration tank with a volume ratio of 10% at the end of the A/O-MBR mode. The mean COD and TN removal efficiencies achieved 96.69 and 32.12% under the AMBR mode, and those were 92.17 and 72.44% under the A/O-MBR mode, respectively. SND (simultaneous nitrification and denitrification) occurred at high MLSS (mixed liquor suspended solids) concentration. The metal membranes reduced effluent COD during filtration. The system ran stably for 115 days at a permeate flux of 0.8-1 m³/(m² d) without changing membranes under the AMBR mode, but the membrane filterability decreased gradually under high MLSS or A/O-MBR mode, and the addition of PVA worsened the membrane filterability on the contrary. PSD (particle size distribution) and sludge fractions had evident influence on membrane fouling. The main fouling mechanism was cake formation under the AMBR mode, and that was pore blocking under the A/O-MBR mode.

Comparative study of polyvinylidene fluoride and PES flat membranes in submerged MBRs to treat domestic wastewater.

Two kinds of membranes, polyvinylidene fluoride (PVDF) and polyethersulfone (PES), were used in submerged flat membrane bioreactors (MBRs) to treat domestic wastewater in this study. The MBRs ran under the same reactor structure, the same membrane pore size of 0.45 mICROm and the same anoxic/ oxic (A/O) process. The experimental results showed that: (1) With the influent of BOD(5) 200-500 mg/L and COD(Cr) 400-1,000 mg/L, PVDF MBR achieved the removal efficiencies of BOD(5) 96-98% and COD(Cr) 89-98%, and those were 97-99% and 93-97% in PES MBR. The interceptive efficiency of PES membrane to BOD(5) and COD(Cr) was superior to PVDF membrane. (2) The removal efficiencies of TN and NH(3)-N in two MBRs exhibited good results which were greater than 85%. The removal efficiencies of TP were greater than 80% in both MBRs. (3) MLSS concentration changed from 2,000 mg/L to 7,000 mg/L during the experiment. PES membrane was not washed and the membrane flux was steady. However, the flux of PVDF one decreased quickly and was washed for twice. It meant that PES membrane had fine capability than PVDF one.

Numerical simulation and visualization experiment of solid particle motion affected by parameters of flow in tapered drum rotating type separator

As the fundamental research work of solid particle motion in the two-phase flow of solid-liquid or gas-liquid in the rotating state, based on the tapered drum rotating type separator and medium of water, the dynamic model of particle motion in the rotating flow filled was set up. Simultaneously, the visualization experiment of particle motion was carried out by the high speed camera and compared with the calculation results. In setting up of dynamic model, besides of forces of gravity, buoyancy, drag force and centrifugal force, the forces of imagination mass force, Basset force, Saffman lift force and pressure gradient force were considered. In the calculation, angle of taper, velocity of down flow and particle size were considered. It is found that the length of drum, angle of taper, down flow speed, rotating speed of drum and particle size had influence on the separating time and the length of particle movement traces. The results were proved by the visualization experiment, and further correctness of dynamic model was validated.

Research and Application on Vibrating Style Drier with Conduction and Heat Transfer

Vibrating style drier with conduction and heat transfer is a novel drying equipment combining drying technology with heat transfer technology. It has the properties of high efficiency, energy saving, environmental protection and fast speed, which overcomes the weakness of large energy consumption of drying equipment and uneven drying of sulfurization bed. It can greatly increase the quality and yield of products, improve the working environment, and increase remarkably economic benefit and energy saving effect. In this paper, the structure characteristics, the working principle, and also the application of vibrating style drier with conduction and heat transfer were introduced. Its dynamic characteristics were analyzed, which was of great significance to the application and popularization of this kind of drier.

Dynamic Model and Numerical Simulation of Particle Motion in Rotation Flow Field of Centrifuge

In this study, in order to determine the size, configuration, rotating speed and other parameters of centrifuge separator, particle motion was simulated by the method of numerical integration of Runge-Kutta. For setting up of dynamic model, besides of forces of gravity, buoyancy, drag force and centrifugal force, the forces of imagination mass force, Basset force, Saffman lift force and pressure gradient force were considered. As the results, it was found that there were some relations among the length of drum, the particle diameter and the revolution of drum. There exist much differences of particle motion between different particles in various sizes. The visualization experiments were carried out to verify the calculated results. The experiment and calculation results were suited well.

Mechanism Study of Excess Sludge Disintegration by Stirred Ball Mill

Stirred ball mill(SBM) method is one of the usually method which applied in large scale application cases of sludge disintegration. This study focuses on investigation the mechanism of sludge disintegration by SBM method. Besides analysis general indicators of SCOD, TN, TP and calculated the disintegration rate of COD (DDCOD). The result indicated the SCOD and DDCOD increased with the disintegration time. As DDCOD increased to the highest of 18.6% at the treated time of 60min, it shown that SBM was not more efficient in disintegration of biomass into so smaller particle that easily dissolved in water.

Degradation of Nonylphenol Polyethoxylates and its Microflora Structure in an Anoxic-Oxic Activated Sludge Process

An anoxic-oxic activated sludge process (AOASP) was carried out to degrade nonylphenol polyethoxylates (NPEOs). The carbon source in influent was replaced stepwise by a mixture of nonylphenol decaethoxylate (M-NP10EO). The 2nd-derivative UV-spectrometry was applied to determine the total amount of M-NP10EO in water samples. Chemical oxygen demand (COD) removal efficiency achieves about 85% under the highest M-NP10EO loading rate, and M-NP10EO removal efficiency is about 80%. Denaturing gradient gel electrophoresis (DGGE) results of activated sludges show that the microbe species decrease but gradually stabilize with the increase of M-NP10EO concentration in influent. Fluorescence in situ hybridization (FISH) results of activated sludges showe that the dominant microflora under the highest M-NP10EO loading rate is β-Proteobacteria (35%), followed by α-Proteobacteria (15%), γ-Proteobacteria (5%) and Actinobateria (4%).