Bio-reduction of N-nitrosodimethylamine (NDMA) using a hydrogen-based membrane biofilm reactor

N-Nitrosodimethylamine (NDMA) is a disinfection by-product shown to be carcinogenic, mutagenic, and teratogenic. A feasible detoxification pathway for NDMA is a three-step bio-reduction that leads to ammonia and dimethylamine. This study examines the bio-reduction of NDMA in a H2-based membrane biofilm reactor (MBfR) that also is active in nitrate and sulfate reductions. In particular, the study investigates the effects of H2 availability and the relative loadings of NDMA, nitrate, and sulfate, which potentially are competing electron acceptors. The results demonstrate that NDMA was bio-reduced to a major extent (i.e., at least 96%) in a H2-based MBfR in which the electron-equivalent fluxes from H2 oxidation were dominated by nitrate and sulfate reductions. NDMA reduction kinetics responded to NDMA concentration, H2 pressure, and the presence of competing acceptors. The most important factor controlling NDMA-reduction kinetics was the H2 availability, controlled primarily by the H2 pressure, and secondarily by competition from nitrate reduction.     

Swine wastewater treatment in a two stage sequencing batch reactor using real-time control

A laboratory scale two-stage sequencing batch reactor (TSSBR) was used to study the effectiveness of pH as a real-time control parameter in swine wastewater treatment. A Ringlace media was inserted into the A/O (Anoxic/Oxic) reactor for bacteria immobilization. The TSSBR was subjected to three levels of organic loading. The pH and ORP (Oxidation Reduction Potential) patterns obtained were consistent with distinct features, enabling the real-time control strategy to effectively set a flexible aeration time pending on influent concentration, hence resulting in flexible cycle time and HRT (Hydraulic Retention Time) for the system. The real-time process ensured a removal efficiency of over 99% and 95%, respectively, for ammonia and TOC (Total Organic Carbon). For NO3(-)-N and PO4(-3), the run with influent TOC = 4,000 mg/L yielded the most efficient removal of 61% and 95%, respectively. Test results suggest that pH can be a viable tool for on-line real-time control of a biological treatment process.     

Optimization of the intermittent aeration in a full-scale wastewater treatment plant biological reactor for nitrogen removal.

The optimization of the intermittent aeration in a full-scale biological reactor treating municipal and industrial wastewater has been studied by means of an experimental design, where the main factors considered have been the on-off period of aeration and the dissolved-oxygen set point. The objective of the work has been to determine the optimal configuration of the aeration control to achieve a simultaneous removal of carbon (expressed as chemical oxygen demand [COD]) and nitrogen. The results were obtained in a full-scale bioreactor located at the wastewater treatment plant of Sant Celoni (Barcelona, Spain), where a nitrogen removal based on a nitrification-denitrification process is being tested. It has been shown that the crucial parameter to ensure a complete removal of COD and nitrogen is to give the system a long time of on-off aeration to complete both the nitrification and the denitrification processes, whereas the dissolved-oxygen set point has a minor influence on the overall performance. The results presented can be applied to a great number of similar systems, in which a nitrogen removal, based on a nitrification-denitrification scheme, is currently being tested or implemented.     

Performance of a full-scale biofilm system retrofitted with an upflow multilayer bioreactor as a preanoxic reactor for advanced wastewater treatment

To enhance nitrogen removal in an existing microbial contact oxidation (MCO) system with a treatment capacity of 900 m3/d, an upflow multilayer bioreactor (UMBR) was chosen as a preanoxic reactor for the removal of organic matter and nitrate. The removal performance of the retrofitted plant was evaluated during the startup phase at a low temperature in winter. The high removal (>80%) of organic matter and suspended solids in the UMBR provided stable nitrification conditions in the MCO system, as a result of the substantial reduction in organic matter and solids loaded onto the MCO system. This treatment system showed a stable nitrogen removal efficiency of 75.3%, even in the low temperature range 7 to 10 degrees C. Phosphorus was completely removed by chemical precipitation. Production rates of excess sludge, as a function of the loads of influent flowrate and biological oxygen demand (BOD), were 0.022 kg dry solid/m3 wastewater and 0.132 kg dry solid/kg BOD.     

Impacts of COD and DCP loading rates on biological treatment of 2,4-dichlorophenol (DCP) containing wastewater in a perforated tubes biofilm reactor

Biofilm processes offer considerable advantages for biological treatment of chlorophenol containing wastewaters since such industrial effluents are difficult to treat by conventional activated sludge processes. A rotating perforated tubes biofilm reactor (RTBR) was developed and used for treatment of 2,4-dichlorophenol (DCP) containing synthetic wastewater. Effects of COD and DCP loading rates on COD, DCP and toxicity removals were investigated. Percent COD removal decreased and effluent COD increased with increasing COD and DCP loading rates due to toxic effects of high DCP content in the feed. DCP and toxicity removals showed similar trends. As the DCP loading rate increased the effluent DCP content increased yielding high toxicity levels in the effluent. COD and DCP loading rates should be below 90gCODm(-2)d(-1) and 2.8gDCPm(-2)d(-1) in order to obtain more than 90% DCP and toxicity removals. However, DCP loading rates lower than 1gDCPm(-2)d(-1) are required to obtain more than 90% COD removal. Empirical equations were developed to estimate percent COD, DCP and toxicity removals as functions of COD and DCP loading rates. The coefficients of the empirical equations were determined by using the experimental data. Empirical model predictions for percent COD, DCP and toxicity removals were in good agreement with the experimental data.     

盐度对序批式反应器与间歇曝气膜生物反应器污水处理效果的影响

采用序批式反应器(SBR)与间歇曝气膜生物反应器(IAMBR)处理模拟生活污水,考察了进水盐度对两反应器污水处理效果的影响。研究表明,当进水盐度为0g/L(以NaCl质量浓度计,下同)时,SBR和IAMBR对总有机碳(TOC)、NH4+-N及TN的去除能力相当,IAMBR未表现出明显的优势;当进水盐度为10g/L时,SBR和IAMBR对TOC、NH4+-N及TN的去除产生明显的差异。IAMBR因为膜的截留与微生物富集作用,对污染物的去除无明显变化,依然保持了较高的污染物去除率,而SBR受盐度冲击影响较大,TOC、NH4+-N及TN的去除率均大幅降低,说明IAMBR具有较高的抗盐度冲击性能。     

Comparison of polyurethane foam and biodegradable polymer as carriers in moving bed biofilm reactor for treating wastewater with a low C/N ratio

This paper presents a comparison between two different materials used as carriers: inert polyurethane (PU) foam and biodegradable polymer polycaprolactone (PCL) particles for the removal of organics and nitrogen from wastewater with a low C/N ratio using moving bed biofilm reactors. The results, during a monitoring period of four months, showed that TOC and ammonium removal efficiency was higher in reactor 2 filled with PU carriers than in reactor 1 filled with PCL carriers (90% and 65% in the former, compared with 72% and 56% in the latter at an hydraulic retention time of 14 h). Reactor 1 showed good behavior in terms of total nitrogen removal as the biodegradable polymer was an effective substrate providing reducing power for denitrification. From three-dimensional excitation-emission matrix analysis, it was shown that the effluent from reactor 1 contained mainly protein-like and soluble microbial product-like substances.     

高色度印染废水和染料废水的脱色新技术应用

应用氧化絮凝复合新技术处理高色度印染废水和染料废水,研究了影响脱色效果的一系列物理化学因素。本技术应用于高色度印染废水和染料废水的脱色处理,可使其脱色率达99％以上,CODcr去除率也在80％以上。     

序批式生物膜反应器不同填料挂膜及短程硝化特性研究

以实际生活污水为研究对象,采用序批式生物膜反应器(SBBR),填充不同种类的填料,针对其各自的挂膜特征和短程硝化的实现与稳定的特性进行了研究.结果表明,与立方体海绵填料相比,炭纤维填料的SBBR能够更快地实现挂膜启动,硝化效果稳定、高效(NH_4~+-N去除率高达99.3%);立方体海绵填料更易在常温下,实现NO_2~--N大量积累的短程硝化,但是相比而言,硝化效率不高.升高温度至30 ℃左右时,能够在30 d内实现炭纤维填料的短程硝化,通过过程控制可以实现短程硝化的稳定.荧光原位杂交技术(FISH)检测结果证实,SBBR中短程硝化的实现与稳定是因为菌群得到了优化,氨氧化细菌成为优势菌种.     

Biofiltration pretreatment for reverse osmosis (RO) membrane in a water reclamation system

Biofouling control is considered as a major challenge in operating membrane systems. A lab-scale RO system was setup at a local water reclamation plant to study the feasibility of using biofiltration as a pretreatment process to control the biofouling. The biological activity in the RO system (feed, product, reject streams) was tested using the standard serial dilution plating technique. Operational parameters such as differential pressure (DP) and permeate flowrate of the system were also monitored. Effects of biofilter on AOC and DOC removals were investigated. Biofiltration was found to be a viable way of assimilable organic carbon (AOC) and dissolved organic carbon (DOC) removals, with removal efficiencies of 40-49% and 35-45% at an empty bed contact time (EBCT) of 30 min. It was also found that using the biofiltration as a pretreatment reduced the rate of biofouling. It took only about 72 h for biofouling to have a significant impact on the performance of the RO membrane, when the system was operated without using biofiltration as pretreatment. There was, however, a five times increase in operational length to more than 300 h when biofiltration was used. This study presented the suitability of the biofilter as an economical and simple way of biofouling control for RO membrane.     

Heavy metal retention and partitioning in a large-scale soil-aquifer treatment (SAT) system used for wastewater reclamation

Soil aquifer treatment (SAT) of wastewater relies on extensive biogeochemical processes in the soil and aquifer to achieve large-scale and economic reclamation of municipal effluents. Removal of trace metals from the wastewater is a prime objective in the operation, but the long-term sustainability of the adsorptive filtration capacity of the soils is an open question. Solid/solution partitioning (measured by the distribution coefficient, K(d)) and solid/solid partitioning (measured by selective sequential dissolution, SSD) of heavy metals were measured in soils sampled from active recharge basins in a wastewater reclamation plant and were compared to the adjacent pristine dune. K(d) values for the adsorption of Cu, Ni and Zn, measured in short-term adsorption experiments positively and significantly correlated with solution pH. Quantitative estimation of Cu, Ni and Zn adsorption on multi-sorbents indicated that surface adsorption and precipitation on Fe oxides and/or carbonate may be the major mechanisms of metal retention in these soils. SSD analyses of metal partitioning in soils exposed to approximately 20yr of effluent recharge showed that all solid-phase components, including the most stable 'residual' component, competed for and retained added Cu and Zn. Copper preferentially partitioned into the oxide component (32.0% of the soil-accumulated metal) while Zn preferentially partitioned into the carbonate component (51.6% of the soil-accumulated metal).     

A dynamic modelling of nutrient metabolism in a cyclic activated sludge technology (CAST) for treating low carbon source wastewater

Environmental Science and Pollution Research - A new mathematical model incorporating biopolymer kinetics and the process of the simultaneous storage and growth are established for the treatment of...     

Uncertainty analysis of parameters for modeling the transfer and fate of benzo(a)pyrene in Tianjin wastewater irrigated areas

A Monte Carlo simulation for uncertainty analysis of three key parameters (local coal consumption rate Q(1L), dry deposition velocity of aerosol particulate Kp and biodegradation rate of benzo(a)pyrene in soil and sediment K(R3)) was conducted in this study. Results of the simulation indicate that the three parameters were influenced by uncertainty and that all equilibrium concentrations in the four bulk compartments and various sub-compartments were log-normally distributed. However, the results also indicated that among the six primary transfer fluxes, erosion associated with solids in soil and deposition associated with solids in water, along with output from sewers were also log-normally distributed, while deposition from air to soil and biodegradation in soil and sediment followed normal distributions. The effect of uncertainty on the model results of the three key parameters was derived using a comparison of upper and lower of confidence interval boundaries at the 95% level of confidence. The results reveal that uncertainty in the key parameters had a more significant influence on equilibrium concentrations of the chemical in the bulk compartments of soil and sediment than on concentrations in the other two bulk compartments, various sub-compartments and the six predominant transfer fluxes.     

Application of a combined response surface methodology (RSM)-artificial neural network (ANN) for multiple target optimization and prediction in a magnetic coagulation process for secondary effluent from municipal wastewater treatment plants

Environmental Science and Pollution Research - In this study, an enhanced coagulation-flocculant process incorporating magnetic powder was used to further treat the secondary effluent of domestic...     

Evaluation of Acinetobacter sp. B9 for Cr (VI) resistance and detoxification with potential application in bioremediation of heavy-metals-rich industrial wastewater

Present work demonstrates Cr (VI) detoxification and resistance mechanism of a newly isolated strain (B9) of Acinetobacter sp. Bioremediation potential of the strain B9 is shown by simultaneous removal of major heavy metals including chromium from heavy-metals-rich metal finishing industrial wastewater. Strain B9 tolerate up to 350 mg L^?1 of Cr (VI) and also shows level of tolerance to Ni (II), Zn (II), Pb (II), and Cd (II). The strain was capable of reducing 67 % of initial 7.0 mg L^?1 of Cr (VI) within 24 h of incubation, while in presence of Cu ions 100 % removal of initial 7.0 and 10 mg L^?1 of Cr (VI) was observed with in 24 h. pH in the range of 6.0–8.0 and inoculum size of 2 % (v/v) were determined to be optimum for dichromate reduction. Fourier transform infrared spectroscopy and transmission electron microscopy studies suggested absorption or intracellular accumulation and that might be one of the major mechanisms behind the chromium resistance by strain B9. Scanning electron microscopy showed morphological changes in the strain due to chromium stress. Relevance of the strain for treatment of heavy-metals-rich industrial wastewater resulted in 93.7, 55.4, and 68.94 % removal of initial 30 mg L^?1 Cr (VI), 246 mg L^?1 total Cr, and 51 mg L^?1 Ni, respectively, after 144 h of treatment in a batch mode.     

Effects of nitrogen with and without acidified sulphur on an ectomycorrhizal community in a Sitka spruce (Picea sitchensis Bong. Carr) forest

This preliminary study investigated the effects of enhanced nitrogen (NH4NO3 at 48 kg ha(-1) y(-1)), sulphur (Na2SO4 at 50 kg ha(-1) y(-1)), acidified nitrogen and sulphur (H2SO4 + NH4NO3) at pre-stated doses (pH 2.5), and acidified nitrogen and sulphur deposition at double these doses on the ectomycorrhizal community associated with a 13-year-old Sitka spruce (Picea sitchensis) forest. Sulphur deposition had little impact on below ground ectomycorrhizal diversity, but stimulated sporocarp production. Nitrogen inputs increased below ground colonisation compared to acidified nitrogen and sulphur, largely due to an increase in Tylospora fibrillosa colonisation. Sporocarp production and ectomycorrhizal root colonisation by Lactarius rufus were reduced in the nitrogen treated plots. These observations suggest that nitrogen deposition to a young plantation may suppress ectomycorrhizal fungi producing large sporocarps. It is proposed that enhanced nitrogen deposition increases ectomycorrhizal nitrogen assimilation, consuming more carbon and leaving less for extrametrical mycelium and sporocarp development.     

Assessing the inhalation cancer risk of particulate matter bound polycyclic aromatic hydrocarbons (PAHs) for the elderly in a retirement community of a mega city in North China

Assessment of the health risks resulting from exposure to ambient polycyclic aromatic hydrocarbons (PAHs) is limited by the lack of environmental exposure data among different subpopulations. To assess the exposure cancer risk of particulate carcinogenic polycyclic aromatic hydrocarbon pollution for the elderly, this study conducted a personal exposure measurement campaign for particulate PAHs in a community of Tianjin, a city in northern China. Personal exposure samples were collected from the elderly in non-heating (August–September, 2009) and heating periods (November–December, 2009), and 12 PAHs individuals were analyzed for risk estimation. Questionnaire and time-activity log were also recorded for each person. The probabilistic risk assessment model was integrated with Toxic Equivalent Factors (TEFs). Considering that the estimation of the applied dose for a given air pollutant is dependent on the inhalation rate, the inhalation rate from both EPA exposure factor book was applied to calculate the carcinogenic risk in this study. Monte Carlo simulation was used as a probabilistic risk assessment model, and risk simulation results indicated that the inhalation-ILCR values for both male and female subjects followed a lognormal distribution with a mean of 4.81?×?10^?6 and 4.57?×?10^?6, respectively. Furthermore, the 95 % probability lung cancer risks were greater than the USEPA acceptable level of 10^?6 for both men and women through the inhalation route, revealing that exposure to PAHs posed an unacceptable potential cancer risk for the elderly in this study. As a result, some measures should be taken to reduce PAHs pollution and the exposure level to decrease the cancer risk for the general population, especially for the elderly.     

Accumulation of potentially harmful elements (PHEs) in lettuce (Lactuca sativa L.) and coriander (Coriandrum sativum L.) irrigated with wastewater: a systematic review and meta-analysis and probabilistic health risk assessment

Environmental Science and Pollution Research - Water shortage and stress around the world lead to increasing wastewater reuse for the agricultural sector. In addition to its benefits, it can be a...     

Semipermeable membrane device (SPMD) for monitoring PCDD and PCDF levels from a paper mill effluent in the Androscoggin River, Maine, USA

Paper mill effluents may contain polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) that are normally generated due to chlorinated bleaching of pulp and paper. We used the semipermeable membrane device (SPMD) to monitor PCDD/F levels upstream and downstream of a paper mill on the Androscoggin River, in Jay (ME). Following the 36 day deployment, SPMD dialysis and cleanup, the samples were analyzed by HRGC/HRMS. Total concentrations of PCDD/Fs in SPMDs (sum of all tetra-through octachlorinated congeners) ranged from 4.71 pg g(-1) to 26.26 pg g(-1). Five out of the targeted 17 toxic congeners were detected, including: 2,3,7,8-TCDF; 1,2,3,7,8-PeCDF; 2,3,4,7,8-PeCDF; 1,2,3,4,6,7,8-HpCDD and OCDD. Permeability reference compounds (PRCs) were used for in situ calibration of the SPMD sampling rate (Rs). In all sites, water concentrations were the highest for OCDD (0.081-0.103 pg l(-1)), and the lowest for 1,2,3,7,8-PeCDF (0.005-0.009 pg l(-1)). There was not a consistent pattern of upstream-downstream gradient in the PCDD/F levels. This suggested that processes other than the mill in Jay (multiple sources, river dynamics) governed the flux of PCDD/Fs in the sampling locations. The SPMD results were validated by comparison to other studies on the Androscoggin River and elsewhere, confirming the potential of the device as a useful monitoring technique for PCDD/Fs in large river systems.