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Nitrogen discharges from decentralized wastewater treatment (DWT) systems contribute to surface and groundwater contamination. However, the high variability in loading rates, long idle periods and lack of regular maintenance presents a challenge for biological nitrogen removal in DWT. A Tire-Sulfur Hybrid Adsorption Denitrification (T-SHAD) process was developed that combines nitrate (NO3(-)) adsorption to scrap tire chips with sulfur-oxidizing denitrification. This allows the tire chips to adsorb NO3(-) when the influent loading exceeds the denitrification capacity of the biofilm and release it when NO3(-) loading rates are low (e.g. at night). Three waste products, scrap tire chips, elemental sulfur pellets and crushed oyster shells, were used as a medium in adsorption, leaching, microcosm and up-flow packed bed bioreactor studies of NO3(-) removal from synthetic nitrified DWT wastewater. Adsorption isotherms showed that scrap tire chips have an adsorption capacity of 0.66 g NO3(-)-N kg(-1) of scrap tires. Leaching and microcosm studies showed that scrap tires leach bioavailable organic carbon that can support mixotrophic metabolism, resulting in lower effluent SO4(2-) concentrations than sulfur oxidizing denitrification alone. In column studies, the T-SHAD process achieved high NO3(-)-N removal efficiencies under steady state (90%), variable flow (89%) and variable concentration (94%) conditions., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Performance of a combined system up-flow anaerobic sludge blanket (UASB) followed by aerobic treatment activated sludge (AS) for removal of carbonaceous and nitrogenous contaminants at an average temperature of 25°C was investigated. The combined system was fed with high strength synthetic sewage having chemical oxygen demand (COD) of 2500 mg L−1. The organic loading rate (OLR) of the UASB reactor was increased gradually from 1.1 to 3.8 gCOD Lr−1d−1. At steady state condition, the UASB reactor achieved removal efficiency up to 83.5% of total COD (CODtot), 74.0% of volatile fatty acid (VFA) and 94.0% of protein. The combined system performed an excellent organic removal pushing the overall removal efficiency of CODtot, VFA and protein to 91.0%, 99.9% and 98.2%, respectively. When the OLR of the UASB increased to 4.4 g COD Lr−1d−1, the UASB was overloaded and; thus, its effluent quality deteriorated. In respect to nitrogen removal, both partial nitrification and complete nitrification took place in aerobic post-treatment. When the dissolved oxygen (DO) concentration was >2.0 mg L−1, complete nitrification (period B) occurred with an average nitrification efficiency of 96.2%. The partial nitrification occurred due to high OLR to AS during the overloading event (period A) and when DO concentration was <2.0 mg L−1(period C). The maximum accumulated nitrite concentration in periods A, B and C were 90.0, 0.9 and 75.8 mg NO−2-N L−1, respectively. The nitrogen balance results of periods A and C indicated that there was a discrepancy between the amount of ammonium nitrogen removed and the amount of oxidized nitrogen formed. This suggests the occurrence of simultaneous nitrification/denitrification (SND) in aerobic post-treatment. [ABSTRACT FROM AUTHOR]

Abstract: Copper is an essential element, however, this heavy metal is an inhibitor of microbial activity at relatively low concentrations. The objective of this study was to evaluate the inhibitory effect of copper(II) towards various microbial trophic groups responsible for the removal of organic constituents and nutrients in wastewater treatment processes. The results of the batch bioassays indicated that copper(II) caused severe inhibition of key microbial populations in wastewater treatment systems. Denitrifying bacteria were found to be very sensitive to the presence of copper(II). The concentrations of copper(II) causing 50% inhibition (IC50) on the metabolic activity of denitrifiers was 0.95mgL−1. Copper was also inhibitory to fermentative bacteria, aerobic glucose-degrading heterotrophs, and nitrifying bacteria (IC50 values=3.5, 4.6 and 26.5mgL−1, respectively). Nonetheless, denitrifying and nitrifying bacteria showed considerable recovery of their metabolic activity after only several days of exposure to high copper levels (up to 25 and 100mg Cu(II) L−1 for denitrification and nitrification, respectively). The recovery could be due to attenuation of soluble copper or to microbial adaptation. [Copyright &y& Elsevier]