owei Gu

Adsorption Characteristics of As(V), Se(IV), and V(V) Onto Activated Alumina: Effects of PH, Surface Loading, and Ionic Strength

Arsenic, selenium, and vanadium are major anionic elements of concern in drinking water. This research investigated the adsorption characteristics of As(V), Se(IV), and V(V) onto a commercial activated alumina (AA) under different pH, surface loading, and ionic strength conditions using batch systems. The results indicated that the adsorption of these elements was significantly affected by pH and the surface loading. However, ionic strength generally did not impact their adsorption, indicating that the electrostatic effect on the adsorption of these elements was relatively not important compared to surface chemical reactions. A speciation-based adsorption model was used to simulate the adsorption of As(V), Se(IV), and V(V) by activated alumina and to determine the adsorption constants of different element species. This model can satisfactorily predict the adsorption of these elements in a broad pH range from 1.5 to 12 and a wide surface loading range from 1.0 to 50 mg/g activated alumina for different sorbent concentrations, using the same set of adsorption constants.

The effects of hydraulic retention time and sludge retention time on the fate of di-(2-ethylhexyl) phthalate in a laboratory-scale anaerobic–anoxic–aerobic activated sludge system

A laboratory-scale anaerobic-anoxic-aerobic (AAA) activated sludge wastewater treatment system was employed to investigate the effects of hydraulic retention time (HRT) and sludge retention time (SRT) on the removal and fate of di-(2-ethylhexyl) phthalate (DEHP). In the range from 5 to 14h, HRT had no significant effect on DEHP removal. However, longer HRT increased DEHP accumulation in the system and DEHP retention in the waste sludge. When SRT was increased from 15 to 25d, DEHP removal efficiency stayed above 96%. Compared to the removal of only 88% at SRT of 10d, longer SRT enhanced DEHP degradation efficiency. The optimal HRT and SRT for both nutrients (nitrogen and phosphorus) and DEHP removal were 8h and 15d. At these retention times, about 71% of DEHP was degraded by the activated sludge process, 26% was accumulated in the system, 2% was released in the effluent, and 1% remained in the waste sludge. The anaerobic, anoxic and aerobic reactors were responsible for 15%, 19% and 62% of the overall DEHP removal, respectively.

The effect of fill mode on the performance of sequencing-batch reactors treating various wastewaters

Abstract The performance of sequencing-batch reactors (SBRs) for the treatment of three kinds of wastewater (synthetic phenolic wastewater, synthetic wastewater containing polyvinyl alcohol (PVA), and effluent from a coke-plant-wastewater treatment system) was investigated. Under low-strength phenol conditions, the performance of the SBR with unaerated fill was superior to the SBR with aerated fill in which filamentous bacteria developed. However, at high influent phenol concentrations, the SBR with unaerated fill accumulated phenol during the fill period to concentrations inhibitory to microorganisms. Fill mode had no significant influence on the performance of SBRs treating PVA-containing wastewater. For the SBRs treating the effluent from a coke-plant-wastewater treatment system, fill mode had no significant impact on the performance of SBRs with respect to organic carbon removal and sludge settleability; but an operating mode which incorporated two anoxic periods, one ahead of the aeration and one after the aeration, was better than other operating modes in terms of nitrogen removal.

Nitrate-dependent biodegradation of quinoline, isoquinoline, and 2-methylquinoline by acclimated activated sludge.

The anaerobic degradation of quinoline, isoquinoline and 2-methylquinoline was investigated under nitrate-reducing conditions with acclimated activated sludge. Quinoline was completely transformed during degradation with an optimum COD/NO(3)-N ratio of 7. Isoquinoline and 2-methylquinoline were also completely transformed; however, nitrate consumption was much lower with the optimum COD/NO(3)-N ratios being in the ranges of 83-92 and 21-26, respectively. GC-MS analyses showed that during degradation, quinoline and isoquinoline were transformed by hydroxylation into 2(1H)-quinolinone and 1(2H)-isoquinolinone, respectively. While quinoline was completely mineralized, only 92% of isoquinoline was mineralized, and 1(2H)-isoquinolinone remained in the effluent. 2-Methylquinoline was transformed by hydrogenation to 1,2,3,4-tetrahydro-2-methyl-quinoline, and further degradation resulted in cleavage of the heterocyclic ring leaving 4-ethyl-benzenamine. Both the metabolites remained in the effluent, resulting in the low mineralization of 2-methylquinoline (58%). This is the first time that 2-methylquinoline is observed degradable under denitrifying conditions, and its metabolites are identified.

Predicting competitive adsorption behavior of major toxic anionic elements onto activated alumina: A speciation-based approach

Toxic anionic elements such as arsenic, selenium, and vanadium often co-exist in groundwater. These elements may impact each other when adsorption methods are used to remove them. In this study, we investigated the competitive adsorption behavior of As(V), Se(IV), and V(V) onto activated alumina under different pH and surface loading conditions. Results indicated that these anionic elements interfered with each other during adsorption. A speciation-based model was developed to quantify the competitive adsorption behavior of these elements. This model could predict the adsorption data well over the pH range of 1.5-12 for various surface loading conditions, using the same set of adsorption constants obtained from single-sorbate systems. This model has great implications in accurately predicting the field capacity of activated alumina under various local water quality conditions when multiple competitive anionic elements are present.

Effect of Temperature on the Sorption of 17α-ethinylestradiol to Aerobic and Anaerobic Sludges

Batch experiments were conducted to measure the sorption capacities of 17α-ethinylestradiol (EE2) to aerobic and anaerobic sludges. The effect of temperature on EE2 sorption was investigated at the temperatures of 10-30°C. The results showed that EE2 sorption equilibrium was reached at 30 min. EE2 sorption on the sludge fitted both Freundlich and linear sorption isotherm models. Distribution coefficients (Kd) of EE2 to aerobic and anaerobic inactivated sludges were 601.9 and 957.0 L/kg at 20°C separately. The effect of temperature on sorption indicated that Kd decreased with the increasing temperature. Kd of EE2 to aerobic and anaerobic inactivated sludges was both decreased by about 50% when temperature increased from 10 to 30°C. The specific sorption coefficient KOM or KOC was also used to describe the sorption capacity, which also decreased with increased temperature. Distribution coefficients (Kd) of EE2 to aerobic inactivated sludge were lower than those of anaerobic inactivated sludge. Sorption thermodynamics indicated that the sorption process was exothermic and spontaneous. Comparatively, sorption isotherms of the aerobic and anaerobic activated sludges were investigated at 20°C. EE2 sorption on activated sludge was also well correlated by both Freundlich and linear sorption isothermal model. Distribution coefficient (Kd) of EE2 to aerobic activated sludge was lower than that of anaerobic activated sludge.

Effects of Pyridine and Methanol on the Biodegradation of 2-methylpyridine by Activated Sludge under Denitrifying Conditions

Lab-scale batch experiments were conducted to investigate the biodegradation of 2-methylpyridine as sole carbon source under denitrifying conditions. Moreover, effects of pyridine and methanol on the biodegradation of 2-methylpyridine were also studied. Under denitrifying conditions, 2-methylpyridine of 100 mg/L was degraded in 13 h as sole carbon source. When pyridine was used as co-substrate with 2-methylpyridine, 2-methylpyridine degradation was inhibited, and pyridine was degraded prior to 2-methylpyridine. On the contrary, methanol promoted the degradation of 2-methylpyridine.

Sorption and Biodegradation of 17beta-Estradiol by Acclimated Activated Sludge under Anaerobic Conditions

The sorption and biodegradation of 17beta-estradiol (E2) was investigated by spiking E2 into acclimated activated sludge under anaerobic conditions in laboratory-scale. The effect of temperature on the sorption and biodegradation was also studied. Results showed that, E2 was removed 99% after 2 h for the tested concentrations (5-15 mugldrL -1 ). E2 sorption followed both the Freundlich and linear sorption models. The distribution coefficient (K d ) was 543.7 Lldrkg -1 at 20degC. E2 degradation was well described by first-order reaction kinetics and the rate constant was 2.765 h -1 at 20degC. Temperature has significant effect on both the sorption and biodegradation of E2 by activated sludge. Distribution coefficient decreased but reaction rate constant increased with the increasing temperature. Partitioning played a significant role in the transfer of E2 between the aqueous phase and the sludge phase. The biodegradation behavior was inside the sludge phase.

Comparison of Naphthalene Sorption Behavior by Three Kinds of Sludge

Lab-scale experiments were conducted to investigate the sorption behavior of naphthalene by anaerobic, anoxic and aerobic sludge. The sorption behavior of naphthalene by different kinds of sludge fitted with several sorption isotherm model well. The maximum sorption capacity of naphthalene sorbed to anaerobic sludge was the largest among the three kinds of sludge.