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N<sub>2</sub>O emission during wastewater nitrification with enriched nitrifying bacteria
Toor, Umair Ali,Han, Dong-Woo,Kim, Dong-Jin Informa UK (Taylor Francis) 2016 Desalination and water treatment Vol.57 No.2
<P>Nitrifying bacteria were enriched in a sequencing batch reactor and used to quantify N2O emission specifically by wastewater nitrification while minimizing or preventing the chances of denitrification during the experiment. Batch wastewater nitrification was carried out in a reactor (working volume 0.5L) at different aeration rates (10 and 20mL/min) and -N concentrations (25, 50, and 100mg/L). Wastewater nitrification efficiencies were more than 97% in all the cases except at 100mg/L with 10mL/min aeration rate (92%). Cumulative N2O emission reached 0.2, 1.15, and 2.67mg (aeration: 10mL/min) and 0.37, 2.18, and 3.08mg (aeration: 20mL/min) at the initial -N concentration of 25, 50, and 100mg/L, respectively. N2O emission yields (kg N2O-N per kg processed -N) were 0.016-0.058 and 0.029-0.088 at 10 and 20mL/min aeration rate, respectively. The yields were higher than that of denitrification. The results showed that cumulative N2O emission and the yield increased at higher ammonium concentration and aeration rate. Accumulated nitrite during nitrification also contributed and played a pivotal role in N2O emission.</P>
Toor Umair Ali,Zubair Ahmed,김동진 한국공업화학회 2014 Journal of Industrial and Engineering Chemistry Vol.20 No.4
Empirical N2O emission correlations were developed from wastewater nitrification in a controlled laboratory scale batch reactor. The results showed that higher concentrations of ammonium and nitrite emitted more N2O. The N2O-N yields were 0.092–0.124 (synthetic wastewater) and 0.124–0.152 kg N2ON/kg consumed NH4+-N (municipal wastewater). Regression analysis showed that N2O emission had positive linear correlation with logarithm of NH4+-N concentration and exponential of NO2 -N concentration. The results indicate that nitrite is the most influential component on N2O emission in wastewater nitrification. The models can be used to estimate and to mitigate N2O emission from wastewater treatment plant.
Toor, Umair Ali,Shin, Hyuna,Kim, Dong-Jin Elsevier 2019 Journal of industrial and engineering chemistry Vol.71 No.-
<P><B>Abstract</B></P> <P>Efficiency of phosphorus recovery from polyaluminum chloride sludge is determined by chemical interactions between Al and P. Chemical structure of Al–P complex and their binding mechanisms in the PAC sludge were investigated with spectroscopy and chemical fractionation. More than 98% of the P was bound with Al, out of which 70% was strongly bound. The ATR-FTIR analysis indicates that the majority of the P formed inner sphere complex with Al through ligand exchange. The availability of highly protonated surface for P sorption at low pH also supports the formation of Al–P outer sphere complex.</P> <P><B>Highlights</B></P> <P> <UL> <LI> PAC sludge contained AlPO<SUB>4</SUB> or related Al–phosphate complex. </LI> <LI> Results showed that 2 types of Al–P bonds are formed in PAC sludge. </LI> <LI> 70% of total Al–P, strongly bound, while 29% was moderate to strongly bound. </LI> <LI> Al–P complex are formed majorly by ISC through ligand exchange mechanism. </LI> <LI> Bidentate binuclear complex followed by monodentate mononuclear and bidentate mononuclear formed at acidic and alkaline pH respectively. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
( Ali Toor Umair ),( Min Wook Kim ),( Dong Jin Kim ) 한국미생물 · 생명공학회 2013 Journal of microbiology and biotechnology Vol.23 No.5
Nitrification in wastewater treatment emits a significant amount of nitrous oxide (N2O), which is one of the major greenhouse gases. However, the actual mechanism or metabolic pathway is still largely unknown. Selective nitrification inhibitors were used to determine the nitrification steps responsible for N2O emission with activated sludge and enriched nitrifiers. Allylthiourea (86 μM) completely inhibited ammonia oxidation and N2O emission both in activated sludge and enriched nitrifiers. Sodium azide (24 μM) selectively inhibited nitrite oxidation and it led to more N2O emission than the control experiment both in activated sludge and enriched nitrifiers. The inhibition tests showed that N2O emission was mainly related to the activity of ammonia oxidizers in aerobic condition, and the inhibition of ammonia monooxygenase completely blocked N2O emission. On the other hand, N2O emission increased significantly as the nitrogen flux from nitrite to nitrate was blocked by the selective inhibition of nitrite oxidation.
Activating natural bentonite as a cost-effective adsorbent for removal of Congo-red in wastewater
Manjot Toor,Bo Jin,Sheng Dai,Vipasiri Vimonses 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1
The bentonite is a widely available and abundant natural mineral, and can be a low cost adsorbent forwater and wastewater treatment. This study reported here was directed towards identifying a costeffectiveactivation protocol for enhancing the adsorption capacity of Australian bentonite for removal oftoxic contaminants in wastewater. We investigated three protocols including thermal activation (TA),acid activation (AA), and combined acid and thermal activation (ATA). The results showed that theseactivation protocols under designed conditions can enhance the surface area and porosity of the rawbentonite. The best ATA protocol considered here brought a 70% increase in the surface area compared to65% and 20% for the best AA and TA protocols, respectively. The optimal ATA protocol identified in thestudy leads to approximately 25% increase in the Congo-red adsorption capacity of the activatedbentonite. This activation method could be a cost-effective approach to enhance the adsorption capacity,applicability and selectivity of natural clay materials,making them as promising and low cost adsorbentsfor wastewater treatment.
Umair Ali Toor,신현아,김동진 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.71 No.-
Efficiency of phosphorus recovery from polyaluminum chloride sludge is determined by chemicalinteractions between Al and P. Chemical structure of Al–P complex and their binding mechanisms in thePAC sludge were investigated with spectroscopy and chemical fractionation. More than 98% of the P wasbound with Al, out of which 70% was strongly bound. The ATR-FTIR analysis indicates that the majority ofthe P formed inner sphere complex with Al through ligand exchange. The availability of highly protonatedsurface for P sorption at low pH also supports the formation of Al–P outer sphere complex.
Recursive Pseudo-Bayesian Access Class Barring for M2M Communications in LTE Systems
Jin, Hu,Toor, Waqas Tariq,Jung, Bang Chul,Seo, Jun-Bae IEEE 2017 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY Vol.66 No.9
<P>Commercial long-term evolution (LTE) systems adopt an access class barring (ACB) mechanism in the initial random access procedure with multiple preambles in order to accommodate bursty traffic arrivals of machine-type communications. In this paper, we propose two Bayesian ACB algorithms that estimate the number of active machine devices based only on the number of idle preambles in each slot. In the commercial LTE systems, eNodeB cannot instantaneously distinguish if a particular preamble is sent from a single device (i.e., success) or multiple devices (i.e., collision). However, the idle preambles can be instantaneously detected at the base station (BS) in each slot. Numerical results show that the proposed algorithms yield quite similar performance with the ideal ACB algorithm, assuming that the exact number of active devices is known to the eNodeB.</P>