Comparison between biological and chemical treatment of wastewater containing nitrogen and phosphorus (original) (raw)
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Wastewater Treatment: Biological
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Journal of Engineering Science and …, 2009
This paper proposes an environmental engineering method based on biotechnology approach as one of the expected solutions that should be considered to implementing the activated sludge for improving the quality of water and living environment, especially to remove the major pollutant elements of domestic wastewater. Elimination of 3 major pollutant elements, i.e., carbon, nitrogen and phosphor containing the domestic wastewater is proposed to carry out biological method of an anoxic-aerobic reactor therein these types of pollutants should be consecutively processed in three steps. Firstly, eliminate the carbonaceous matter in the aerobic reactor. Secondly, to remove the carbonaceous and nitrogenous matters, it is necessary to modify the reactor's nature from the aerobic condition to an anoxic-aerobic reactor. And finally, when the cycle of nitrification-denitrification is stable to achieve the target's efficiency of reactor by adding the ferric iron into the activated sludge, it can be continued to remove the carbonaceous, nitrogenous and phosphorous matters simultaneously. The efficiency of carbonaceous and nitrogenous matters removal was confirmed with the effluent standard, COD is less than 100 mgO 2 /L and the value of global nitrogen is less than 10 mgN/L. The effectiveness of suspended matter removal is higher than 90% and the decantation of activated sludge is very good as identifying the Molhman's index is below of 120 mL/L. The total phosphorus matter removal is more effective than the soluble phosphorus matter. By maintaining the reactor's nature at the suitable condition, identifying the range of pH between 6.92 and 7.16 therefore the excellent abatement of phosphor of about 80% is achieving with the molar Fe/P ratio of 1.4.
Biological Nutrient Removal in Municipal Wastewater Treatment: New Directions in Sustainability
Journal of Environmental Engineering, 2012
To control eutrophication in receiving water bodies, biological nutrient removal (BNR) of nitrogen and phosphorus has been widely used in wastewater treatment practice, both for the upgrade of existing wastewater treatment facilities and the design of new facilities. However, implementation of BNR activated sludge AS systems presents challenges attributable to the technical complexity of balancing influent chemical oxygen demand (COD) for both biological phosphorus (P) and nitrogen (N) removal. Sludge age and aerated/unaerated mass fractions are identified as key parameters for process optimization. Other key features of selected BNR process configurations are discussed. Emerging concerns about process sustainability and the reduction of carbon footprint are introducing additional challenges in that influent COD, N, and P are increasingly being seen as resources that should be recovered, not simply removed. Energy recovery through sludge digestion is one way of recovering energy from influent wastewater but which presents a specific challenge for BNR: generation of sidestreams with high nutrient and low COD loads. Technologies designed specifically to treat these side-stream loads are overviewed in this paper. Finally, relatively high levels of nitrous oxide emissions, a powerful greenhouse gas, have been shown to occur in the BNR process under certain conditions, particularly in the presence of high nitrite concentrations. The advantages of using process modeling tools is discussed in view of optimizing BNR processes to meet effluent requirements and to meet goals of sustainability and reducing carbon footprints.
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International Journal of Environmental Science and Technology
Because different phosphorus (P) forms vary greatly in their bioavailability, total phosphorus concentrations are a problematic predictor of the eutrophication potential of natural surface waters and wastewater treatment facility effluents. It is currently not known which operational P characterizations (i.e., dissolved/particulate and reactive/non-reactive) best predict effluent P bioavailability. We characterized the P speciation and directly measured the bioavailability of P (BAP) using algal bioassays for 14 full-scale advanced nutrient removal wastewater treatment plants representing a wide range of P removal technologies. A strong statistical relationship was observed between the effluent total BAP (tBAP) and total reactive P (TRP) (r 2 & 0.81), with a tBAP/TRP ratio of 0.61 ± 0.24, indicating that TRP can be used as a conservative surrogate predictor of tBAP. A comparison of different operational categories for phosphorus indicated that sBAP is consistently lower than both soluble P (SP) and soluble reactive P (SRP) with average ratios of 0.34 ± 0.19 and 0.62 ± 0.27, respectively. This shows a large fraction of the dissolved non-reactive P (i.e., SP-SRP), and C40 % of the P classified as SRP was not bioavailable. Total BAP concentrations were on average 30 % higher than soluble BAP (sBAP) concentrations, indicating that the particulate P fraction was an important component of the BAP for the tested effluents. Comparisons between different P removal technologies suggest the bioavailability, and P species composition varies with the nutrient removal process, and that in many cases, a large portion ([60 %) of the effluent P is recalcitrant to algal growth.