Enhancing nitrate and phosphorus removal from stormwater in fold-flow bioretention system with saturated zones

The traditional bioretention systems possess a remarkably low nitrogen and phosphorus removal effect. The removal rate fluctuates greatly, and even appears as negative removal of nitrogen and phosphorus. The four simulated bioretention experimental columns with different bilayer media, packing composition and structure were constructed. Based on the traditional fillers, the modified composite fillers with hydroxy-aluminum and modified vermiculite sludge particle (HAVSP) were added. The traditional filler (C1) and the modified composite filler (C2) were added respectively, moreover the saturated zones were set up to enhance the effect of nitrogen and phosphorus removal. Removal of nutrients from experimental columns by simulated runoff efficiency was evaluated and compared. In addition, the effect of media depth on phosphorus retention and denitrifying enzyme activity in bioretention columns was also evaluated. The experimental column #2 filled with C2 had the optimum removal effect on total phosphorus (93.70%), however, the removal effect of total phosphorus by filling C1 experimental columns was insufficient (57.36%). Designed to remove nitrate (NO3−-N) and total nitrogen (TN), the experimental column #4 showed the best performance (83.54% and 92.15%, respectively). In this study, we propose a fold-flow bioretention system by filling HAVSP in combination with saturated zones. The runoff water quality can be effectively improved, and a new bioretention cell configuration can be provided for efficient stormwater treatment.

Evaluation of Siltation Degree of Permeable Asphalt Pavement and Detection of Noise Reduction Degree

This study mainly uses PFC (particle follow code) to simulate the void characteristics of permeable asphalt mixture, and uses these to simulate the silting process. Then, a tire drop test was used to evaluate the noise reduction performance of permeable asphalt concrete. Finally, a self-made ring rutting test machine was used to simulate the silting process. Through experiments, the following conclusions were obtained: 1. The critical size of the sludge particle size is 0.3 mm–0.6 mm. 2. The quality of the water-permeable asphalt concrete specimens increased by 13% before and after silting, and the porosity of the specimens finally decreased from about 20% to about 8%. The water-permeable function only retained less than 20% of the original, and the water-permeable function was basically lost. 3. By measuring the road noise detection, it was found that the road noise is directly proportional to the degree of blockage of the permeable road. Compared with the original road with a perfect permeable function, the road noise of the completely blocked road increased by about 4 decibels. This study reveals the silting process of permeable asphalt mixture and the key particle size of the silt, which is of great significance for the detection, cleaning and maintenance of permeable asphalt pavements.

The Production of Biodiesel from Sewage Sludge Via Soxlet Extraction Using Hexane and Ethyl Acetate in Ratio 2:1 As the Organic Solvent and Transesterification Reaction

The Lipid/oil was extracted from reduced dried primary sewage sludge particle using soxhlet extraction method with Hexane and Ethyl Acetate in the ratio 2:1 as the extracting solvent. The extracted oil gave 15.03% percentage yield with density of 0.845 g/ml, pH value of 8.97, specific gravity of 0.845, viscosity of 41.20 mm2/sec, kinematic viscosity of 42.18 mm2/sec. The lipid/oil was brownish black in colour with a pungent smell. The chemical analyses revealed saponification value of 168.00 mgKOH/g, acid value of 5.60 mgKOH/g and free fatty acid value of 2.80%. The physicochemical analyses of the biodiesel produced gave a c percentage yield of 40% biodiesel, density of 0.845 Kg/ml, pH value of 8.50, specific gravity of 0.845, kinematic viscosity of 4.80 mm2/s, acid value of 0.37 mg KOH/g, and flash point of 150°C, cloud point of 5°C and pour point of -2°C. The results of the physicochemical parameters from the research shows that the feedstock (primary sewage sludge) would be a good source for the production of biodiesel.

Long-Term Investigation into the Membrane Fouling Behavior in Anaerobic Membrane Bioreactors for Municipal Wastewater Treatment Operated at Two Different Temperatures

In this study, the characteristics of activated sludge flocs were investigated and their effects on the evolution of membrane fouling were considered in the anaerobic membrane bioreactors (AnMBR), which were operated at 25 and 35 °C for municipal wastewater treatment. It was found that the membrane fouling rate of the AnMBR at 25 °C was more severe than that at 35 °C. The membrane fouling trends were not consistent with the change in the concentration of soluble microbial product (SMP). The larger amount of SMP in the AnMBR at 35 °C did not induce more severe membrane fouling than that in the AnMBR at 25 °C. However, the polysaccharide and protein concentration of extracellular polymeric substance (EPS) was higher in the AnMBR at 25 °C in comparison with that in the AnMBR at 35 °C, and the protein/polysaccharide ratio of the EPS in the AnMBR at 25 °C was higher in contrast to that in the AnMBR at 35 °C. Meanwhile, the fouling tendencies measured for the AnMBRs could be related to the characteristics of loosely bound EPS and tightly bound EPS. The analysis of the activated sludge flocs characteristics indicated that a smaller sludge particle size and more fine flocs were observed at the AnMBR with 25 °C. Therefore, the membrane fouling potential in the AnMBR could be explained by the characteristics of activated sludge flocs.

APPLICATION OF THE FLOCCULATION PROCESS FOR THE MUNICIPAL SEWAGE SLUDGE TREATMENT

<p>All municipal sewage treatments using classic treatment chain create an amount of organic sludge. The stabilization/neutralization of them is essential before any conditioning or reuse. For agronomical recycling or energy-giving optimization, the sludge needs to correspond to some standards. That's why, it exist several treatment of stabilization, packaging and water extraction of sludge. This study deals with sludge chemical conditioning by flocculation process. In the first hand, the flocculation process allows to break up colloidal aversion between particles in sludge. This process is possible by charge neutralization thanks to synthetic or natural organic flocculation which is often cationic since the ionic force of sludge particle usually is negative and the flocculants can be used with lowest dose than common coagulant like aluminum sulfate or ferric chloride. Thanks to laboratory experiments by analysis of several doses of synthesis cationic flocculants, it has been possible to get performance on total suspended solids (TSS), by spectrophotometry measurement and consistency of sludge cake. Graphical analyses allow making comparison between some organic cationic flocculants and select the best one for this type of sludge and the kind of treatment used. The aim is to improve quality of sludge, quantity of filtrated volume, and quality of water.</p>

Comparison of ferric chloride and aluminum sulfate on phosphorus removal and membrane fouling in MBR treating BAF effluent of municipal wastewater

A membrane bioreactor (MBR) was used for treating biological aerated filter effluent in a municipal wastewater plant, and chemical phosphorus removal was accomplished in the MBR. The results showed that ferric chloride of 20 mg/L and aluminum sulfate of 30 mg/L were the optimal dosages for total phosphorus (TP) removal, and the TP removal efficiency was over 80%. In long-term continuous operations, both ferric chloride and aluminum sulfate effectively mitigated membrane fouling, with the corresponding growth rate of transmembrane pressure decreased to 0.08 and 0.067 kPa/d, respectively. Sludge particle sizes analysis demonstrated that the decrease of particle sizes lower than 50 μm was the main reason for membrane fouling control. Simultaneously, the proteins and polysaccharide (PS) concentrations in the MBR supernatant were analyzed, and the PS concentration significantly decreased to 2.02 mg/L at aluminum sulfate of 30 mg/L, indicating the flocculation of aluminum sulfate on PS was the main reason for mitigation of membrane fouling.

Fluidization Characteristic of Sewage Sludge Particles

The main objective of this study is to determine the basic characteristics of fluidization using sewage sludge particle as non-visual phenomena which can then be modeled physically and numerically with the program of Computational Fluid Dynamic (CFD). CFD modeling using Eulerian model incorporating the kinetic theory for solid particles was applied to the gas-solid flow at various superficial velocities for different particle sizes. The transfer momentum was calculated using Syamlal-O'Brien drag function and Eulerian multiphase model was used for analysis. Two-Dimensional computational domains discretized using rectangular cells (Quad), made within the 20 iteration steps of 0,001s. The gas velocity is found to be the ​​the most important factors that influence the formation process of fluidization; by increasing the rate of fluidization the bed expanse occurs higher as well the time of onset fluidization is shorter. The phenomenon can be explained well by modeling and simulation.