Selection of sustainable wastewater treatment scenarios under different local contexts is a complex process because of the inherent trade-offs among socio-economic, environmental and technical as well as functional factors. In order to fulfill conflicting yet complementary objectives, an integrated and systematic approach called the "multi-criteria analysis" (MCA) using a multi-dimensional set of criteria and life cycle assessment (LCA) tools as effective decision support mechanisms for integrated evaluation and selection of sustainable small-town wastewater treatment systems has been developed. Application of this approach was illustrated through a case study of the small Vietnamese town Toan Thang, with an estimated total population of 10,000 people. A short-list of 3 selected scenarios and a multi-dimensional set of criteria facilitated a complex decision-making process. The qualitative analysis results presented in the spider-web diagram as well as the quantitative analysis results from various impact assessments have indicated clearly that the use of waste stabilization ponds is ranked as the first priority and seems to be the most promising and sustainable choice for the town under consideration. The results obtained from this study can be used as a scientific basis and could be valuable inputs for stakeholders' consultation and preference assessment in searching for the most suitable solution under their local context.
Acute and subchronic toxicity experiments of tributyltin chloride (TBTCl) were conducted with the marine harpacticoid copepod Tigriopus japonicus. The 48-hr LC50 and highest non-lethal concentration (NOLC) for adult females were 0.96 and 0.14 μg/L, respectively, whereas these values for adult males were 0.58 and 0.07 μg/L, respectively. For the mean cumulative number of nauplii produced per female, the 14-day highest no observed effect concentration (NOEC), lowest observed effect concentration (LOEC) and EC50 were 0.025, 0.05 and 0.055 μg/L, respectively. The acute-subchronic ratio, i.e. the ratio of the 48-hr LC50 for adult females to the 14-day highest NOEC, MATC (maximum acceptable toxicant concentration) and LOEC, was 38.5, 27.2 and 19.3, respectively. These results suggest that the concentrations of current ambient TBT (tributyltin) compounds in Japanese coastal waters can be assumed as the safety range for the survival, but are unlikely to cause a reduction in the number of nauplii produced per female of T. japonicus. The high concentrations in seawaters, sediments and/or seawaters released from sediments that have been observed in estuarine and coastal waters in Japan may lead to a considerable reduction of survival and numbers of nauplii produced by females for T. japonicus.
Giant reed (Arundo donax) is a perennial, gramineous plant that has high biomass production potential. In this study, we focused on its applicability as a raw material for the production of adsorbents for the purification of cadmium-contaminated water. Charcoals were prepared from the stalk of the giant reed at various temperatures (400 - 700°C) under nitrogen stream. Analysis of pore size distribution based on methanol vapor adsorption revealed that the mesopores within the range of 20 to 100 Å were abundant in charcoals prepared under 400°C and 500°C. Using these charcoals, the removal capacity of cadmium from aqueous solution was investigated. As a result, high removal capacity under low concentration of cadmium was observed. High yield of cadmium with 0.01 N hydrochloric acid treatment was also clarified. X-ray diffraction (XRD) analysis revealed that Cd(OH)2 existed on the surface of the cadmium-adsorbed charcoal. The possible mechanism of the "apparent adsorption" was discussed.
Adsorptive removal of selenate from aqueous phase using ZrIV-loaded orange waste gel was investigated. Adsorption kinetics showed that equilibrium was attained within 2 and 4 h for 12 and 23 mg/L of SeVI, respectively. A pseudo-second-order kinetic model was found to characterize the adsorption kinetics for all the initial selenium concentrations tested. Adsorption isotherms at various pH values were examined and the data fitted well with Langmuir model. The maximum sorption capacity was found to be 25 mg/g at optimum pH. The adsorption system was found to be favorable with separation factors between 0 and 1. Competitive adsorption by coexisting anions showed that chloride barely affected SeVI adsorption while phosphate and sulfate impeded SeVI adsorption. A ligand exchange mechanism was inferred for SeVI adsorption.
There is a need to conduct more research on the degradability of pharmaceuticals and personal care products in environmental waters for controlling water pollution and sustaining water system. In this study, we added tetracycline to 6 water samples, incubated the samples in the laboratory, and determined the degradation rates and bacterial growth in each sample for analysis of the growth of tetracycline-resistant or tetracycline-degrading bacteria and the mechanism of tetracycline degradation. The main conclusions obtained in this study can be summarized as follows: (1) The maximum degradation of tetracycline was in the Unoke River water samples with 60% degradation in the sample with the initial tetracycline concentration of 1 mg/L. (2) Not all bacteria growing in the water environment containing tetracycline were capable of degrading the antibiotic. (3) The ability of bacteria to degrade tetracycline in environmental water systems may be useful in microbial source tracking.
Arsenic (As) that has been accumulated from irrigation groundwater to paddy field soil by sorption has the potential for food contamination by plant uptake and recontamination of the groundwater. This study evaluated the effect of calcium (Ca) and magnesium (Mg) addition on As leaching from paddy field soil collected from the southwest region of Bangladesh. Batch experiments were employed to systematically investigate the role of Ca and Mg addition on the leaching behavior of As under different concentrations of Ca and Mg, pH conditions and anaerobic incubation. Results indicated that As leaching was highly decreased with the increase of Ca and Mg addition, at pH greater than 9.0 and during anaerobic incubation. In contrast, Iron (Fe) leaching was decreased by Ca and Mg addition. Adsorption of Ca and Mg was observed and significant correlation with adsorbed As was obtained in all batches. The probable mechanism was precipitation of As due to the increase in the positive surface charge of the Fe hydroxide solids by Ca and Mg adsorption. This study also indicated that Ca and Mg addition could decrease As leaching even under the presence of phosphorus.
Two biotic ligand models (BLMs) predicting copper accumulation and toxicity to heavy metal tolerant moss (Funaria hygrometrica Hedw.) were developed in the present study. Although BLMs developed in this study could predict the effects of pH and calcium on copper accumulation and toxicity, stability constants representing the binding strength between cations and the biotic ligand for the toxicity model were different than those for the accumulation model. Stability constants of copper, calcium and proton for the toxicity model were logKCu = 2.98, logKCa = 3.38, and logKH = 4.17, respectively, and for the accumulation model were logKCu = 4.46, logKCa = 3.28, and no effect, respectively. Proton competition with copper accumulation was not observed. Difference in logKCu between the two models indicated that tolerance with copper results in the decrease in KCu. In addition, it was indicated that decreases in copper toxicity due to increases in proton concentration was not caused by the competitive effects of proton but by the changes in internalization flux.
Japan's recommended method of EDTA determination is complex and time-consuming. In this study, a new method to prepare the solution to determine EDTA in water by solid-phase extraction-GC/MS was developed. Recovery yields were excellent with values ranging from 98.1 to 100.5%. Due to this method's ease and simplicity, it is suggested that this approach be adopted as Japan's recommended method for EDTA analysis. The method was applied to assess the concentrations of EDTA in river water from three regions of Japan. Median concentration of EDTA in river water samples was 115 μg/L, and the concentrations ranged from 18.8 to 443 μg/L. The highest concentration of EDTA (443 μg/L) was observed in Tsurumi River. Sewage treatment plant (STP) effluent significantly contributed to high EDTA levels.
This paper assessed the possible reuse of used hand warmer contents (HWCs) as a nitrate retardation material in porous media. Under saturated and unsaturated flow conditions, column experiments with a pulse source of potassium nitrate solution were conducted in silica sand and Andisols with a mixture of HWCs. Mixture of HWCs and flow velocities in a flow field were varied in order to investigate the relation between the degree of retardation and the amount of HWCs under the approximately one order range of Reynolds number. Experimental breakthrough curves measured by capillary electrophoresis were analyzed using temporal moments to estimate the dispersion coefficient, retardation factor and distribution coefficient. The results of column experiments showed that the increase in the amount of HWCs added resulted in the increase of the first two temporal moments and retardation factor in both soils, particularly in silica sand. Reuse of HWCs would be useful to alleviate an immediate leaching of nitrate with high concentration to groundwater in a sandy medium rather than in an aggregated medium.
Presence of the antiviral drug oseltamivir in considerable concentrations in surface waters especially in seasonal and pandemic influenza cases has raised concerns on its possible consequences in the environment and human health. This investigation aimed to elucidate concentration levels of the drug in Neya River in Osaka during 2009/2010 seasonal influenza. Oseltamivir phosphate was detected for the first time in Neya River suggesting the presence of the drug in phosphate form in surface waters is significant only in influenza pandemic cases. Oseltamivir carboxylate concentrations in Neya River were as high as 15-fold the concentrations in Yodo River in 2007/2008 and 3-fold the concentrations in a sewage treatment plant effluent in Kyoto in 2008/2009. The highest oseltamivir carboxylate concentration in Neya River was detected at ST-2 (864.8 ng/L) followed by ST-3. This was possibly due to the inefficiency of the treatment plant upstream and low river water flowrate. Based on the limited information available on the possible environmental risks of the drug in surface waters, the detected concentrations in Neya River may not be an immediate threat to the environment. However, detailed risk assessment studies are essential to clarify the potential environmental risk issue.
Different sources of wastewater and soil were used to screen for PHA-producing bacteria using biodiesel-derived waste glycerol as a sole carbon source by the Nile red staining method together with polymer determination. Twelve out of twenty-six isolates from biodiesel-contaminated wastewater consortium were screened for their PHA accumulation ability by cultivation in mineral salt medium supplemented with waste glycerol. The AIK7 isolate was chosen as a potential PHA producer. The PHA production on waste glycerol was examined using pure glycerol as a control substrate. The PHA content of AIK7 isolate cultivated in 10 g/L glycerol could reach 35% cell dry weight in 72 hours from waste glycerol and 33% cell dry weight in 120 hours from pure glycerol cultivation. It can be seen that at this content of waste glycerol, AIK7 isolate is effectively capable of biotransforming glycerol into polymer from low-grade glycerol.
Laboratory scale experiments operated by the EBPR (enhanced biological phosphorus removal) process with coagulant addition were carried out to clarify the effects of coagulant on phosphorus uptake and release as well as the stabilization of phosphorus removal efficiency in the EBPR process using sequencing batch reactors. Phosphorus was removed without Fe addition, however, standard deviation of effluent PO4-P concentration was high and the phosphorus removal performance was generally unstable. Phosphorus removal was stable with the Fe addition. The PO4-P concentrations at the end of the anaerobic phase with Fe addition were lower than those concentrations without Fe addition. The phosphorus uptake rates at the aerobic phase with Fe addition were higher than those concentrations without Fe addition. These indicated that coagulant addition could decrease the phosphorus concentration at the end of anaerobic phase and enhance the phosphorus uptake rate during aerobic phase. These contributed to the stabilization of the phosphorus removal in the EBPR process. Addition of Fe with Fe/P molar ratio of 0.2 was enough to stabilize the phosphorus removal efficiency. The molar ratio was extremely small compared to the usual amount of the coagulant added in the activated sludge process.
The seasonal effects of nutrient loading from migratory waterfowl on water and the successive changes of the aquatic ecosystem based on each biomass of phytoplankton, zooplankton and submerged macrophytes were surveyed in Tsubasa Pond, Yonago Waterbird Sanctuary, Japan. The pond's water quality gradually deteriorated with the influx of migratory waterfowl. The concentration of total nitrogen corresponded rapidly with waterfowl biomass. Peak concentrations of total phosphorus and chlorophyll a (Chl.a) were observed about one month later when the migratory waterfowl had flown away. After one month, the peak concentration of Chemical Oxygen Demand (CODMn) appeared. Thus, the water quality of the pond had gotten worst after the waterfowl had flown away. Then, decrease of Chl.a concentration and increase of zooplankton density were observed in spring. In summer, the population of a submerged macrophyte increased temporarily and water quality recovered. These results indicated that the primary producer in the bird sanctuary pond alternated from phytoplankton to submerged macrophyte in one year.
Naturally occurring processes such as biological reaction might modify the properties of dissolved organic matter (DOM) for binding with heavy metals. Complexation of heavy metals with DOM determines their environmental and ecological impacts. In this study, biodegradation experiments were carried out separately for river water and river water spiked with DOM in wastewater treatment plant (WWTP) effluent to evaluate the biological alteration of zinc complexation characteristics of DOM under river water environment. Zinc complexation parameters, conditional stability constant and binding site concentrations were determined using anodic stripping voltammetry with Scatchard linearization. Total ambient zinc binding site concentration of river water DOM was reduced from 410 nM to 74 nM (82% decline) during two weeks of incubation. Compared to the river water DOM, 1-month incubation of DOM in WWTP effluent under the river water environment, showed only 22% decline in total ambient Zn binding sites. On the other hand, conditional stability constants, for Zn binding sites of DOM from WWTP effluent, did not vary during 1 month of incubation. The result suggests that metal (Zn) binding sites of DOM from WWTP effluents are biologically persistent in the urban river water environment.
Physicochemical coagulation process is one of the most popular techniques to remove phosphorus in wastewater treatment processes where the activated sludge was used. However, the influence of coagulants on biological nitrification is not elucidated in detail. Then, the influence of polyferric sulfate as coagulant on nitrogen conversion by ammonia oxidizer was investigated by using water quality test and transcript analysis. In the batch operation of the nitrification-denitrification process, Fe/P molar ratios of 0, 1 and 5 were tested. Phosphorus concentration was immediately decreased at the beginning of the experiment in the case of Fe/P = 1 and 5, however, 40% of ammonia remained in the case of Fe/P = 5. In this case, the amoA mRNA expression was suppressed because of the excessive addition of polyferric sulfate. Furthermore, T-RFLP profiles of amoA mRNA showed that polyferric sulfate affects various species of ammonia oxidizer, and some species suffer a great loss.
The relation between the denitrification rate and quinone compositions of the microorganisms in the water treatment apparatus for paddy drainage was evaluated. Q-8 content, the highest ubiquinone, had the strongest correlation coefficient between the denitrification rate (DNR) and the detected ubiquinone. MK-7 had the strongest correlation with DNR among the detected menaquinones. From the results of principal component analysis for DNR using quinone content as the variables, the first principal components were Q-8 and Q-9, and the second principal component was MK-8. Q-8, Q-9, MK-7 and MK-8 containing bacteria strongly contribute to DNR in the water treatment apparatus and around the paddy environment.