Nitrate Removal from Groundwater by Denitrification in Fixed and Fluidized Bed Biofilm Reactors A Comparative Study

The influence of attached biomass bioreactor types on the denitrification process using a low-pitched groundwater containing nitrates was studied. Two types of fixed-bed and fluidized-bed biofilm reactors, equipped with expanded clay granular filler, with a particle size fraction of 2-5 mm were used. The nitrite and nitrate concentrations in the inflow and outflow of the two bioreactors were analytically determined. Based on the obtained concentration values, the denitrification rates were calculated, ranging between 1275�1387 g NO3-N/m3/day in the case of the fixed bioreactor and between 3390�3867 g NO3-N/m3/day in the case of the fluidized bed bioreactor.

An Investigation of Attached Biomass on Bio-Media using Scanning Electron Microscopy

Biological film that attached to bio-media in attached growth wastewater treatment processes needs to be monitored and evaluated as it reflects the performance of the plant. Using Scanning Electron Microscopy (SEM) is an effective way for the examination of biofilms. Three different types of bio-media (bio-balls) were used to study the biofilm thickness using SEM. They are fin ball, spike ball and cage ball. Each type of bio-balls was cut into pieces since the size of SEM sample must be less than 25 mm. The fin ball was cut into three pieces, the spike ball was cut into two pieces and the cage ball was cut into one piece. Only the non-identical parts from the bio-balls were chosen for SEM test. The cut pieces with biofilm growth were overnight dehydrated in laboratory oven before bring to the SEM for measuring and analysis of the thickness of biofilm growth. Based on average biofilm thickness of the cut pieces extracted from SEM test, cage ball and fin ball recorded the highest biofilm while spike ball has the lowest biofilm growth on it.

Modeling Power Generation and Energy Efficiencies in Air-Cathode Microbial Fuel Cells Based on Freter Equations

The model proposed in this study was based on the assumption that the biomass attached to the anode served as biocatalysts for microbial fuel cell (MFC) exoelectrogenesis, and this catalytic effect was quantified by the exchange current density of anode. By modifying the Freter model and combining it with the Butler–Volmer equation, this model could adequately describe the processes of electricity generation, substrate utilization, and the suspended and attached biomass concentrations, at both batch and continuous operating modes. MFC performance is affected by the operating variables such as initial substrate concentration, external resistor, influent substrate concentration, and dilution rate, and these variables were revealed to have complex interactions by data simulation. The external power generation and energy efficiency were considered as indices for MFC performance. The simulated results explained that an intermediate initial substrate concentration (about 100 mg/L under this reactor configuration) needed to be chosen to achieve maximum overall energy efficiency from substrate in the batch mode. An external resistor with the value approximately that of the internal resistance, boosted the power generation, and a resistor with several times of that of the internal resistance achieved better overall energy efficiency. At continuous mode, dilution rate significantly impacted the steady-state substrate concentration level (thus substrate removal efficiency and rate), and attached biomass could be fully developed when the influent substrate concentration was equal to or higher than 100 mg/L at any dilution rate of the tested range. Overall, this relatively simple model provided a convenient way for evaluating and optimizing the performance of MFC reactors by regulating operating parameters.

Modeling Power Generation and Energy Efficiencies in Air-Cathode Microbial Fuel Cells Based on Freter Equations

The model proposed in this study was based on the assumption that the biomass attached to the anode served as biocatalysts for MFC exoelectrogenesis, and this catalytic effect was quantified by the exchange current density of anode. By modifying the Freter model and combining it with the Butler-Volmer equation, this model could adequately describe the processes of electricity generation, substrate utilization, and the suspended and attached biomass concentrations, at both batch and continuous operating modes. MFC performance is affected by the operating variables such as initial substrate concentration, external resistor, influent substrate concentration, and dilution rate, and these variables were revealed to have complex interactions by data simulation. The external power generation and energy efficiency were considered as indices for MFC performance. The simulated results explained that an intermediate initial substrate concentration (about 100 mg/L under this reactor configuration) needed to be chosen to achieve maximum overall energy efficiency from substrate in the batch mode. An external resistor with the value about that of the internal resistance boosted the power generation, and a resistor with several times of that of the internal resistance achieved better overall energy efficiency. At continuous mode, dilution rate significantly impacted the steady-state substrate concentration level (thus substrate removal efficiency and rate), and attached biomass could be fully developed when the influent substrate concentration was equal to or higher than 100 mg/L at any dilution rate of the tested range. Overall, this relatively simple model provided a convenient way for evaluating and optimizing the performance of MFC reactors by regulating operating parameters.

Water Quality Enhancement in Ponds Using Baffles, Burullus in Egypt as a Case Study

This study investigated the simulation of hydrodynamics water quality in waste stabilization ponds (WSPs) after using baffles. The major functions performed by baffles are to reduce hydraulic short-circuiting and to provide a submerged surface, which can encourage the growth of attached biomass. Attached biomass growing on the surface of the baffles could increase the total mass of organisms in the pond, thus improve the treatment efficiency and therefore reduce the eutrophication rate in the pond such as NH3-N, NO3-N &PO4-P. In this research, mathematical model (MIKE21) developed by (DHI), was formulated to simulate water quality parameter. The study applied on Burullus Lake, which is the second largest northern lake in Egypt, which belongs to high eutrophic lake type and suffers from several problems. Results showed that there is a significant variance between the rate of values without and after making baffles. The findings indicated that the percentage removal of NH3-N, NO3-N &PO4-P are (51.8, 43.7 &40.1%) respectively in the case of no overlap between baffles, to be (83.4, 94.3 & 89.6%) in the case of overlap ratio 0.95 at the high temperature. This result suggests that the overlap between baffles is more efficient to reduce the eutrophic rate in the water. In conclusion, waste ponds can be improved easily and economically to be more efficient by making baffles.

Study of Convert Waste Stabilization Pond Geometry to Treated Wastewater Efficiency, (El- Burullus Lake, Egypt) As a Case Study

The simulation of hydrodynamics water quality in ponds is a developing tool that worth studying in order to understand their internal processes and interactions. Pond design involves several physical, hydrological, geometrical, biological and dynamic variables to provide high hydrodynamic efficiency and maximum substrate utilization rates. Computational fluid dynamic modelling (CFD) allows the combination of these factors to predict the behavior of ponds by using different configurations. In this research mathematical model developed by Danish Hydraulic Institute (DHI), was formulated to simulate WQ parameter. This model was calibrated and used to simulate a scenario to improve study reach water quality in polluted lakes. The study applied on El-Burullus Lake, which is the second largest northern lake in Egypt which belongs to high eutrophic lake type and suffers from several problems. The model was run at steady and variable state with raw wastewater to study the real effect of the polluted drains, which discharge high amount of polluted wastewater into the El-Burullus Lake and know the lake situation after make baffles scenario. The major functions performed by baffles are to reduce hydraulic short-circuiting and to provide a submerged surface which can encourage the growth of attached biomass. Attached biomass growing on the surface of the baffles could increase the total mass of organisms in the pond and thus improve the treatment efficiency and therefore reduce the eutrophication rate in the pond such as (NH3-N, PO4-P and NO3-N). Results showed that there are a significant variance between the rate of NH3-N, PO4-P and NO3-N before and after make baffles, and the overlap between baffles (L=0.50 baffle) is more efficient than no overlap. In conclusion, waste ponds and be improved easily and economically to be more efficient by making baffles in the lake which can increase the water velocity, avoided the dead zones area and reduce the eutrophic concentration.