Test of Membrane Aerated Biofilm Reactors for Nitrogen Removal in Wastewater Treatment

Membrane aerated biofilm reactor, as a biological wastewater treatment technology, has been nearly mature on a commercial scale. It uses bubble-free aeration to provide oxygen for biological nitrification and wastewater degradation. A novel oxygen-permeable hollow fiber membrane (Zeelung cord) specifically designed for use in a membrane aerated biofilm reactors (MABR). These fibers are organized into bundles, which are wrapped around the reinforcing core to increase strength. This permeable membrane allows oxygen to diffuse into the attached biofilm, which directly leads to the biological oxidation of pollutants in the wastewater. This study aimed to determine the nitrification and oxygen transfer capacity of Zeelung fibers used in the MABR system. The effects of various C/N ratios (in the range of 1.0 to 3.0) on the membrane modules were studied using three laboratory-scale reactors over the course of 165 days. In this test, the average removal efficiency of COD can reach 74% under selected conditions, up to 90%. Meanwhile, the average nitrification rate is 3.9 g/d/m2, the average ammonia removal rate is 90%, and the maximum value can reach 99%. In addition, the oxygen transfer rate of the fiber in the liquid phase was 19.65 g/d/m2. The experiment also indicated that the nitrification rate is directly proportional to the transfer flux of oxygen and is related to the content of dissolved oxygen in the water. The nitrification rate can be controlled by controlling the concentration of dissolved oxygen in water, thus affecting the removal rate of ammonia nitrogen.

Water aeration researches using fine air bubble generators

The paper presents experimental researches able to demonstrate that the aeration installations with mobile fine bubble generators are more efficient than the classic ones with fixed, fine bubble generators. The paper develops water aeration researches by introducing two types of fine air bubble generators: I. Fixed fine air bubble generators, which generate Ø <1 mm bubbles; II. Mobile fine air bubble generators that move in the volume of water subject to aeration. The theoretical and experimental results are presented for the two versions. According to experimental data, aeration with mobile FBG is more efficient in terms of oxygen transfer from atmospheric air to a stationary water mass.

Determination of the Optimal Parameters of the Jet Aeration

To ensure effective aeration of the biological wastewater treatment process, easy-to-operate and not too energy-intensive units are needed. Jet aerators have such capabilities. In this study, the authors searched for the best hole shape for the aeration nozzles. It was determined that a nozzle with an elongated hole has the largest size of the actively aerated zone. Experimental studies of nozzles of a diameter of 56 mm with nozzles of elongated shape showed that the best characteristics of mass transfer are provided by nozzles with a total area of holes of 356 mm2 at a flow rate of 10 … 12 m/s. For practical calculations, an equation was obtained for the dependence of the oxygen transfer coefficient KLa(20) on the complex criterion vn, and a method for calculating aeration units was developed, which is applicable for aerators with elongated holes.

Experimental Oxygen Mass Transfer Study of Micro-Perforated Diffusers

We studied new micro-perforated diffuser concepts for the aeration process in wastewater treatment plants and evaluated their aeration efficiency. These are micro-perforated plate diffusers with orifice diameters of 30 µm, 50 µm and 70 µm and a micro-perforated tube diffuser with an orifice diameter of 50 µm. The oxygen transfer of the diffuser concepts is tested in clean water, and it is compared with commercial aerators from the literature. The micro-perforated tube diffuser and micro-perforated plate diffusers outperform the commercial membrane diffusers by up to 44% and 20%, respectively, with regard to the oxygen transfer efficiency. The most relevant reason for the improved oxygen transfer is the fine bubble aeration with bubble sizes as small as 1.8 mm. Furthermore, the more homogenous cross-sectional bubble distribution of the micro-perforated tube diffuser has a beneficial effect on the gas mass transfer due to less bubble coalescence. However, the pressure drop of micro-perforated diffusers seems to be the limiting factor for their standard aeration efficiencies due to the size and the number of orifices. Nevertheless, this study shows the potential for better aeration efficiency through the studied conceptual micro-perforated diffusers.