The large quantity of river benthic community data, which were aggregated by the Ministry of the Environment (MOE) and the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) of Japan, were examined to evaluate river environments from the viewpoint of biodiversity. A set of biodiversity indicator taxa was proposed and validated using the MLIT data. Next, a biodiversity classification index was created by dividing the data into 4 classes according to the distribution of the number of indicator taxa collected in the MOE surveillance. This enabled the evaluation of the health of the sampling site using the MOE-water quality and biodiversity classes. It became apparent that the two evaluation indices were not completely dependent variables, although they had an effect on each other at some level. The relationships between certain conditions of the river environment and the two evaluation indices were also analyzed, which revealed that biodiversity cannot be evaluated using BOD values or riverbed morphology. Moreover, it was found that the sampling site condition tended to deteriorate as the BOD value increased and as the size of the riverbed material decreased. Consequently, basic and valuable information to conserve the river environment was obtained.
The removal of Se(VI) from a simulated wet flue gas desulfurization (FGD) wastewater was attempted by the use of a photocatalytic reduction system. Conventional method of removal, such as adsorption by ion-exchange resins, was not effective for Se(VI) removal from wastewater. The photocatalyst reduction system consisted of TiO2 and HCOOH as a photocatalyst and an electron hole scavenger, respectively. When the photo-irradiation was performed for a Se(VI) solution under the system, an efficient removal of Se(VI) was achieved, suggesting that the reduction of Se(VI) actually occurs via the photocatalytic system to produce Se(0) precipitate. The photocatalytic reduction system could be applied to Se(VI) removal from the simulated wastewater. However, excess amount of HCOOH was needed to achieve efficient Se(VI) removal from wastewater.
Allelopathic potential by a submerged macrophyte Potamogeton pusillus against Microcystis aeruginosa in actual ponds was evaluated. The culture filtrate of P. pusillus inhibited the growth of M. aeruginosa, suggesting that P. pusillus released allelochemicals. For the evaluation of allelopathic potential in actual ponds, water samples collected in and out of vegetated mesocosm were examined by a novel bioassay method. Also, allelopathic potential of water obtained from vegetated and unvegetated mesocosm was compared. As a result, water in P. pusillus-vegetated mesocosm showed an obvious growth-inhibiting effect on M. aeruginosa but not in unvegetated mesocosm and out of mesocosm. The water obtained from two ponds, Yamanokami and Bessho Pond, confirmed these effects. The results indicated allelopathic effect by P. pusillus community worked in actual ponds or lakes and the effect lasted as long as P. pusillus inhabited.
For developing a multipurpose Botryococcus braunii utilization system, in which water purification and biofuel production will be achieved simultaneously, the growth behavior of B. braunii under a simulated open-air condition was clarified, where Microcystis aeruginosa was assumed to coexist. Microcystis aeruginosa is one of the typical algae in eutrophic water. The monoculture experiments revealed that the growth rate of a B. braunii strain was lower than that of a microcystin-producing M. aeruginosa strain under various phosphate concentrations. Meanwhile, the phosphate uptake rate of B. braunii was higher than that of M. aeruginosa. In the batch monoculture experiments, the promising hydrocarbon production of B. braunii was observed within a wide range of initial phosphate concentrations (11 to 216 mg-PO43-/L). In the two-algal species mixed culture experiments, the growth characteristics were different with the coexisting species. When a non-microcystin-producing M. aeruginosa strain was cultured with B. braunii, the domination of M. aeruginosa within the experimental period was observed especially in the cases where the initial biomasses of M. aeruginosa were high compared to those of B. braunii. On the other hand, when microcystin-producing M. aeruginosa was cultured with B. braunii, the abundant microcystin production was observed without domination of M. aeruginosa. These results suggested the importance of the effective utilization of the high phosphate uptake ability of B. braunii, and the control of the initial biomass ratio of algae for the realization of B. braunii system under the open-air condition.
Sewage can be considered one of the richest and most productive waters for crops since it contains nitrogen (5 - 7%) and phosphorus (3 - 5%) and in constructed wetlands it could be used as fertilizer. The feasibility of growing corn on a recirculating vertical flow constructed wetland (RVFCW) treating sewage on-site was examined. Corn was planted at 107,000 seeds/ha. Effluents from a septic tank and a RVFCW were analyzed for water quality variables. Treatment efficiencies (removal) were high for fecal coliform bacteria (99.9%), biochemical oxygen demand (98.4%), total suspended solids (95.6%), ammonium-nitrogen (95.3%), total Kjeldhal nitrogen (94.7%), total nitrogen (79.5%), and total phosphorus (75.5%), while relatively low for potassium (48.8%). Corn yield (only kernel) was 10,026 kg/ha. These results show that a RVFCW could be a sustainable alternative technology to grow corn providing a mechanism to remove pollutants from wastewater, reduce sanitation problems, and improve economic and social benefits.
An oil palm fiber module has been developed to modify a down-flow hanging sponge (DHS) reactor module. The objective of the proposed system is to improve two existing DHS variants of post-treatment unit for UASB treating domestic wastewater, i.e. cube-type and curtain-type sponge as domestic wastewater treatment system for developing countries. This paper describes the potential of oil palm fiber-based DHS (PF-DHS) configuration for sewage treatment. Feasibility of the PF-DHS reactor was evaluated by conducting a six-month continuous operation using actual sewage as feed. The system has been verified to have an excellent organic removal performance achieving 67% of unfiltered COD removal, and nearly perfect SS removal at the HRT of 2 h. It was observed that the organic removal rate was approximately 2.64 kg COD/m3 per day. The result recommended that the proposed PF-DHS reactor would be a promising system to alter sponge-based DHS for domestic wastewater treatment system in developing countries.
A composting toilet, using sawdust as a matrix, has the potential to trap pathogens that might occasionally be contained in human feces. Therefore, care must be taken when handling the sawdust. High temperature and low water content conditions are effective for reducing pathogen content. However, it is not clear whether these effective conditions can cause lethal damage to these pathogens or not. Therefore, the present study investigates the inactivation mechanisms of pathogens in a composting toilet, using E. coli as a model of pathogenic bacteria and Qβ as a model of pathogenic viruses. Escherichia coli was rapidly and lethally inactivated under high pH conditions. In dry conditions, they were inactivated lethally but not rapidly. High temperature treatment was unable to inactivate them lethally. For Qβ, the capsid was mainly damaged under high temperature and dry conditions, whereas high pH conditions primarily damaged nucleic acids. Therefore, raising the pH was an effective way to rapidly and lethally reduce both pathogenic bacteria and viruses.
This study examines the photodegradation of PCB 153 under ultraviolet radiation and ultraviolet radiation combined with hydrogen peroxide (H2O2) using a batch tubular recirculating photoreactor equipped with 17 W and 24 W UV-C lamps emitting at 254 nm. PCB 153 solutions with various concentration of 50 ppb, 80 ppb and 100 ppb were prepared for experiments conducted under photolysis (UV only) while 25 μL (0.221 mM), 50 μL (0.441 mM), 75 μL (0.662 mM) of 30% (w/w) H2O2 were individually added to an 80 ppb PCB 153 solution and used as samples for UV/H2O2 experimental runs. Under ultraviolet radiation, the increase of light intensity from 17 W to 24 W increased the degradation from 90.43% to 94.71% of an 80 ppb aqueous PCB 153 solution after 2 hrs of irradiation. The addition of 50 μL (0.441 mM) of 30% wt H2O2 resulted into a drastic decrease of the same concentration of PCB 153. After 30 minutes of irradiation using 17 W UV lamp, 95.95% PCB degradation was observed while complete degradation was attained with the 24 W UV lamp. The pH of the solutions was closely monitored and it was observed that it decreases during photodegration. The decrease of the sample's pH was a result of inorganic chlorides and acidic metabolites formation as measured using High Performance Liquid Chromatography (HPLC) - Conductivity Detector. Likewise, the PCB concentration of irradiated samples was measured using Gas Chromatography equipped with Electron Capture Detector (GC-ECD).
The effect of external carbon (acetate) addition on nitrogen and phosphorus removal in a sequencing batch reactor (SBR) employing anaerobic/oxic/anoxic (AOA) regime was investigated. Two SBRs, receiving wastewater with different total organic carbon per nitrogen concentration (TOC/N) ratios (influent TOC/N ratio: 2.2 and 4.5 in Run 1 and Run 2, respectively) were operated by changing the amount of external carbon addition at the beginning of oxic phase. The operations in both reactors revealed that nitrogen and phosphorus removal efficiencies increased with an increase in external carbon addition, reaching more than 90% at an external carbon addition of 45.0 mg-C/L. Moreover, the ratio of anoxic/oxic phosphate uptake rate (PUR), an index reflecting a fraction of denitrifying phosphate-accumulating organisms (DNPAOs) in total PAOs, indicates that nitrogen and phosphorus removal efficiencies were enhanced as the PUR ratio increased. Quantitative fluorescence in situ hybridization (FISH) revealed that external carbon addition facilitated the activity of DNPAOs as well as that of glycogen-accumulating organisms (GAOs). The degree of nitrogen removal by denitrifying GAOs (DNGAOs) seemed to increase with an increase in the dosage of external carbon added.
An azo dye, Orange II was decolorized and degraded by two-stage-treatment of chemical reduction by using zero-valence tin and biological oxidation. Zero-valence tin decolorized Orange II under acidic conditions, and produced the two aromatic amines, p-aminobenzene sulphonic acid (ABS) and 1-amino-2-naphthol (1A2N). By the enrichment culture using ABS and/or 1A2N as the sole carbon source, ABS-degrading consortium and Pseudomonas aeruginosa m2 as 1A2N-degrading bacterium were obtained. When the co-culture of P. aeruginosa m2 and ABS-degrading consortium was performed in the decolorized solution of Orange II by tin, the isolated strains exerted their degradation activities against each aromatic amine during the co-culture. The recalcitrant complex which was formed between ABS and 1A2N through auto-oxidation remained during the co-culture time. However, the elimination of the complex and the enhancement of ABS degradation were observed when tin was mixed in the co-culture.