Self-build packed-bed bioreactor for rapid and effective BOD estimation

This work demonstrated a simple, low-cost, rapid, and effective biochemical oxygen demand (BOD) estimation system based on a packed-bed bioreactor that can be easily self-built on-site at a particular wastewater treatment plant for continuous monitoring of the influent and effluent. The use of natural microbial consortium that were collected from the target wastewater and immobilized on a cheap porous carrier simply by adhesion resulted in an acceptable accuracy of over 95%. The newly developed semi-continuous operating mode with peak-type signals was shown to be able to continuously estimate BOD at a high flow rate to overcome the flow dependence of the oxygen electrode, limit clogging issues, enhance the response time, and lower the limit of detection. The resulting packed-bed bioreactors could work continuously for 22 h with a coefficient of variance (CoV) of only 1.8% or for 13 h a day for several days with a maximum CoV of 1.4% and their response was observed to be stable over 80 consecutive measurements. They exhibited stable responses at a wide pH range of 6.5–8.5, which is also the recommended range for aerobic wastewater treatment, emphasizing the greater ease of use of natural microorganisms for BOD estimation.

     

Indirect prediction of surface ozone concentration by plant growth responses in East Asia using mini-open top chambers

We developed small and mobile open top chambers (mini-OTC) measuring 0.6 m (W)?×?0.6 m (D)?×?1.2 m (H) with an air duct of 0.6 m (W)?×?0.23 m (D)?×?1.2 m (H). The air duct can be filled with activated charcoal to blow charcoal filtered air (CF) into the chamber, as opposed to non-filtered ambient air (NF). Ozone sensitive radish Raphanus sativus cv. Red Chime and rosette pakchoi Brassica campestris var. rosularis cv. ATU171 were exposed to NF and CF in mini-OTCs at different locations in East Asia. A total of 29 exposure experiments were conducted at nine locations, Shanghai, China, Ha Noi, Vietnam, Lampang, Phitsanulok and Pathumtani, Thailand, and Hiratsuka, Kisai, Abiko and Akagi, Japan. Although no significant relationships between the mean concentrations of ambient O₃ during the experimental period and the growth responses were observed for either species, multiple linear regression analysis suggested a good relationship between the biomass responses in each species and the O₃ concentration, temperature, and relative humidity. The cumulative daily mean O₃ (ppb/day) could be indirectly predicted by NF/CF based on the dry weight ratio of biomass, mean air temperature, and relative air humidity.     

Determination of an acceptable assimilable organic carbon (AOC) level for biological stability in water distribution systems with minimized chlorine residual

There is considerable interest in minimizing the chlorine residual in Japan because of increasing complaints about a chlorinous odor in drinking water. However, minimizing the chlorine residual causes the microbiological water quality to deteriorate, and stricter control of biodegradable organics in finished water is thus needed to maintain biological stability during water distribution. In this investigation, an acceptable level of assimilable organic carbon (AOC) for biologically stable water with minimized chlorine residual was determined based on the relationship between AOC, the chlorine residual, and bacterial regrowth. In order to prepare water samples containing lower AOC, the fractions of AOC and biodegradable organic matter (BOM) in tap water samples were reduced by converting into biomass after thermal hydrolysis of BOM at alkaline conditions. The batch-mode incubations at different conditions of AOC and chlorine residual were carried out at 20°C, and the presence or absence of bacterial regrowth was determined. The determined curve for biologically stable water indicated that the acceptable AOC was 10.9 μg C/L at a minimized chlorine residual (0.05 mg Cl₂/L). This result indicated that AOC removal during current water treatment processes in Japan should be significantly enhanced prior to minimization of the chlorine residual in water distribution.     

Application of soft computing to predict water quality in wetland

Prediction of water quality is a critical issue because of its significant impact on human and ecosystem health. This research aims to predict water quality index (WQI) for the free surface wetland using three soft computing techniques namely, adaptive neuro-fuzzy system (ANFIS), artificial neural networks (ANNs), and group method of data handling (GMDH). Seventeen wetland points for a period of 14 months were considered for monitoring water quality parameters including conductivity, suspended solid (SS), biochemical oxygen demand (BOD), ammoniacal nitrogen (AN), chemical oxygen demand (COD), dissolved oxygen (DO), temperature, pH, phosphate nitrite, and nitrate. The sensitivity analysis performed by ANFIS indicates that the significant parameters to predict WQI are pH, COD, AN, and SS. The results indicated that ANFIS with Nash-Sutcliffe Efficiency (NSE = 0.9634) and mean absolute error (MAE = 0.0219) has better performance to predict the WQI comparing with ANNs (NSE = 0.9617 and MAE = 0.0222) and GMDH (NSE = 0.9594 and MAE = 0.0245) models. However, ANNs provided a comparable prediction and the GMDH can be considered as a technique with an acceptable prediction for practical purposes. The findings of this study could be used as an effective reference for policy makers in the field of water resource management. Decreasing variables, reduction of running time, and high speed of these approaches are the most important reasons to employ them in any aquatic environment worldwide.

     

Visualization and quantification of transparent exopolymer particles (TEP) in freshwater using an auto-imaging approach

Most water sources are full of microscopic transparent exopolymer particles (TEP), which are currently regarded as a major initiator of biofilm formation. This study developed and applied an auto-imaging FlowCAM-based method for online observation and quantification of TEP in freshwater. Samples from reservoirs in Taiwan with a wide range of water quality were directly used to develop this methodology. Factors that potentially affect the measurement were tested. The results showed that characteristics of the particles measured instantaneously after staining samples with Alcian blue differed significantly from those measured at steady states, as a result of particle aggregation. Compared to traditional microscopic methods, this proposed method provides a simple, rapid, and less labor-intensive analysis with particle morphological conservation and a large number of particle attributes. By overcoming the limitations from the former, this technique would offer routine monitoring of these transparent particles from various freshwater sources and feed water in membrane filtration, hence facilitating the use of TEP as a critical parameter for biofouling investigation in water treatment. Application of the method for Taiwan reservoirs showed a wide variety of morphological forms of TEP and its abundance, up to 25,000 ppm.     

Impact of simulated acid rain on the growth of three species Brassica integrifolia,Brassica rapa,Brassica juncea in Hanoi,Vietnam

Environmental Science and Pollution Research - Over the past decade, the extent and magnitude of acid rain in Vietnam and other Asian countries have become more apparent. In this study, the effect...     

Phthalic acid esters (PAEs) in workplace and house dust from Vietnam: concentrations,profiles, emission sources,and exposure risk

Environmental Science and Pollution Research - The occurrence of nine phthalic acid esters (PAEs) were determined in indoor dust samples collected from vehicle repair shops, waste processing...     

CHARACTERIZATION OF PARTICULATE MATTER EMISSION FROM OPEN BURNING OF RICE STRAW

Emission from field burning of crop residue, a common practice in many parts of the world today, has potential effects on air quality, atmosphere and climate. This study provides a comprehensive size and compositional characterization of particulate matter (PM) emission from rice straw (RS) burning using both in situ experiments (11 spread field burning) and laboratory hood experiments (3 pile and 6 spread burning) that were conducted during 2003-2006 in Thailand. The carbon balance and emission ratio method was used to determine PM emission factors (EF) in the field experiments. The obtained EFs varied from field to hood experiments reflecting multiple factors affecting combustion and emission. In the hood experiments, EFs were found to be depending on the burning types (spread or pile), moisture content and the combustion efficiency. In addition, in the field experiments, burning rate and EF were also influenced by weather conditions, i.e. wind. Hood pile burning produced significantly higher EF (20±8 g kg(-1) RS) than hood spread burning (4.7±2.2 g kg(-1) RS). The majority of PM emitted from the field burning was PM(2.5) with EF of 5.1±0.7 g m(-2) or 8.3±2.7 g kg(-1) RS burned. The coarse PM fraction (PM(10-2.5)) was mainly generated by fire attention activities and was relatively small, hence the resulting EF of PM(10) (9.4±3.5 g kg(-1) RS) was not significantly higher than PM(2.5). PM size distribution was measured across 8 size ranges (from <0.4 μm to >9.0 μm). The largest fractions of PM, EC and OC were associated with PM(1.1). The most significant components in PM(2.5) and PM(10) include OC, water soluble ions and levoglucosan. Relative abundance of some methoxyphenols (e.g., acetylsyringone), PAHs (e.g., fluoranthene and pyrene), organochlorine pesticides and PCBs may also serve as additional signatures for the PM emission. Presence of these toxic compounds in PM of burning smoke increases the potential toxic effects of the emission. For illustration, an estimation of the annual RS field burning in Thailand was made using the obtained in situ field burning EFs and preliminary burning activity data.     

Plant extract-mediated synthesis of aluminum oxide nanoparticles for water treatment and biomedical applications: a review

Environmental Chemistry Letters - Nanotechnologies have contributed to disease control and prevention, but conventional synthesis of nanoparticles rarely meets the strict requirements of green...     

Polychlorobenzenes and polychlorinated biphenyls in ash and soil from several industrial areas in North Vietnam: residue concentrations,profiles and risk assessment

Polychlorinated benzenes (PCBzs) including penta- and hexachlorobenzene can be unintentionally formed from thermal processes in different industrial activities, and very little information is available on the contamination and emission characteristics of these new persistent organic pollutants from industries in Vietnam. In this study, contamination of PCBzs (including penta- and hexachlorobenzene, named PeCBz and HCB, respectively) and PCBs (including CB-28, 52, 101, 153, 138, 180) in fly ash, bottom ash and soil from combustion processes of waste incineration, metallurgy (steel making and zinc production) and cement production from several provinces in the Northern Vietnam, including Hai Duong, Hanoi, Bac Ninh, Hai Phong and Thai Nguyen, was preliminary investigated. The PCBzs concentrations in fly ash, bottom ash and soil ranged from 2.7 to 100 ng g^?1, from 2.7 to 159 ng g^?1 and from 0.28 to 33.9 ng g^?1, respectively. Relatively high residues of PeCBz in fly ash and bottom ash from municipal waste incinerators in some provinces from the Northern Vietnam were encountered. Total PCBs concentrations ranged from 18.0 to 8260 ng g^?1, from 1.0 to 10600 ng g^?1 and from 14.5 to 130 ng g^?1 for the fly ash, bottom ash and soil, respectively. Daily intakes of PeCBz, HCB and PCBs through soil ingestion and dermal exposure estimated for children ranged 0.33–9.93 (mean 3.14), 0.39–21.1 (mean 4.9) and 6.09–1530 ng/kg bw/day (mean 346), respectively; and these intakes were about 4.7–5.4 times higher than those estimated for adult. The intakes of PeCBz and HCB were relatively low, while those for PCBs exceeded WHO TDI for some samples.