Hiroaki Furumai

Direct and indirect inactivation of microcystis aeruginosa by UV-radiation

Excessive algal growth in drinking water sources like lakes and reservoirs is responsible for filter-clogging, undesirable taste and odor, disinfection-by-product formation and toxin generation. Although various methods are currently being used to control algal bloom, their successes are limited. Some water utilities routinely use copper sulfate to control excessive algal growth. But there is a growing concern against its use mainly because it is non-specific to target algae and kills many non-target species. In this study, the scope of using UV-radiation to control algal growth was assessed using Microcystis aeruginosa as test species. A UV-dose of 75 mW s cm(-2) was found to be lethal to M. aeruginosa. A smaller dose of 37 mW s cm(-2) prevented growth for about 7 days. It was found that UV-radiation may increase the specific gravity of the cells and thus may adversely affect the ability of the cells to remain in suspension. Three days after a UV-dose of 75 mW s cm(-2), almost all the cells settled to the bottom of the incubation tubes, whereas all the unirradiated cells remained in suspension. It was also observed that UV-radiation on algal extracellular products has a significant residual effect and can contribute to algal growth control. The extent of residual effect depends on the UV-dose and can continue even for 7 days. UV-radiation was found to produce H2O2 in the microM level concentration. But at such level, H2O2 itself is not likely to cause the residual effect that was found in this study.

Multiple evaluations of the removal of pollutants in road runoff by soil infiltration.

Groundwater replenishment by infiltration of road runoff is expected to be a promising option for ensuring a sustainable urban water cycle. In this study, we performed a soil infiltration column test using artificial road runoff equivalent to approximately 11-12 years of rainfall to evaluate the removal of pollutants by using various chemical analyses and bioassay tests. These results indicated that soil infiltration treatment works effectively to remove most of the pollutants such as organic matter (chemical oxygen demand (CODMn) and dissolved organic carbon (DOC)), P species, polycyclic aromatic hydrocarbons (PAHs), numerous heavy metals and oestrogenic activities. Bioassay tests, including algal growth inhibition test, Microtox and mutagen formation potential (MFP) test, also revealed effective removal of toxicities by the soils. However, limited amounts of NO3, Mn, Ni, alkaline earth metals, perfluorooctane sulphonate (PFOS) and perfluorooctane sulphonamide (FOSA) were removed by the soils and they possibly reach the groundwater and cause contamination.

Validation of internal controls for extraction and amplification of nucleic acids from enteric viruses in water samples.

ABSTRACT Inhibitors that reduce viral nucleic acid extraction efficiency and interfere with cDNA synthesis and/or polymerase activity affect the molecular detection of viruses in aquatic environments. To overcome these significant problems, we developed a methodology for assessing nucleic acid yields and DNA amplification efficiencies for environmental water samples. This involved adding particles of adenovirus type 5 and murine norovirus and newly developed primer-sharing controls, which are amplified with the same primer pairs and result in the same amplicon sizes as the targets, to these samples. We found that nucleic acid loss during the extraction process, rather than reverse transcription-PCR (RT-PCR) inhibition, more significantly attributed to underestimation of the presence of viral genomes in the environmental water samples tested in this study. Our success rate for satisfactorily amplifying viral RNAs and DNAs by RT-PCR was higher than that for obtaining adequate nucleic acid preparations. We found that inhibitory properties were greatest when we used larger sample volumes. A magnetic silica bead-based RNA extraction method effectively removed inhibitors that interfere with viral nucleic acid extraction and RT-PCR. To our knowledge, this is the first study to assess the inhibitory properties of environmental water samples by using both control virus particles and primer-sharing controls.

Evaluation of microbial regrowth potential by assimilable organic carbon in various reclaimed water and distribution systems

Microbial regrowth introduces several problems to the use of reclaimed water, such as health concerns, aesthetic deterioration, and biofouling. This study evaluated assimilable organic carbon (AOC), which is a part of the biodegradable organic matter promoting microbial growth, in water reclamation systems in Japan. The AOC concentration in the reclaimed water from various treatment processes ranged between 36 and 446 μg C/L (median 316 μg C/L). The AOC concentration in the reclaimed water from the plants equipped with ozonation was significantly higher - more than two times - than that in the reclaimed water from plants equipped with other processes. UV and chlorine also changed the AOC concentration slightly. Moreover, reverse osmosis produced reclaimed water with the lowest AOC content. Processes equipped with membrane filtration were effective in removing seed microorganisms that enter the distribution system. Microbial growth in reclaimed water distribution systems occurred when the total and free residual chlorine was lower than 0.36 and 0.09 mg/L, respectively. The AOC reduction occurred simultaneously with regrowth, which suggests that AOC could support microbial growth in reclaimed-water-distribution systems. As the residual chlorine is often depleted during distribution and storage, it is essential to control the AOC to suppress microbial growth.

Extracellular polymers of hydrogen-utilizing methanogenic and sulfate-reducing sludges

Abstract Extracellular polymers (ECP) play an important role in biological wastewater treatment. They are believed to be responsible for the formations of flocculent activated sludge as well as anaerobic granules. In this study, the ECP characteristics of two types of enrichment cultures were examined. One enriched culture was composed of hydrogenotrophic methanogens (HM) alone while the other was composed of HM and hydrogenotrophic sulfate-reducing bacteria (HSR). Both cultures were enriched through a series of 107 repeated batches using H 2 CO 2 plus, in the HM/HSR series, sulfate and nutrients. At various stages of the enrichment process, the ECP were extracted from the sludge samples and analyzed for their protein (ECPp) and carbohydrate (ECPc) contents. Results showed that in the mixed culture HM consumed 67% of hydrogen and HSR 33%. The net yields of biomass for HM and HSR cultures were 0.046 g-VSS/g-COD and 0.059 g-VSS/g-COD, respectively. Productions of ECP were dependent upon substrate. Glucose-degrading sludge produced more ECP than the HM culture, which in turn produced more than the HSR culture. The net ECP yields for HM culture were 1.06 mg-ECPp/g-COD and 0.64 mg-ECPc/g-COD, respectively; the corresponding yields for HSR culture were 0.74 mg-ECPp/g-COD and 0.52 mg-ECPc/g-COD. For the enriched HM culture, more ECPp, as well as ECPc but to a lesser degree, were produced at the beginning of each batch when high concentration of hydrogen was available. This was, however, not noticeable for the HSR culture.

Surface charge and extracellular polymer of sludge in the anaerobic degradation process

Changes of surface charge and extracellular polymer (ECP) content were investigated in batch experiments for three anaerobic sludges, each of which had been enriched at 35°C and pH 639-7.3 for more than 40 batches using propionate, butyrate and glucose, individually, as the sole substrate. Results showed that both ECP and the negative surface charge were dependent on the growth phase of microorganisms. They increased at the beginning of all batches when the microorganisms were in the prolific-growth phase, having high substrate concentration and food-to-microorganisms ratio. Both later gradually returned to their initial levels when the microorganisms were in the declined-growth phase, as the substrate became depleted. The negative surface charge increased linearly with the total-ECP content in all series with slopes of 0.0187, 0.0212 and 0.0157 meq/mg-total-ECP for sludge degrading propionate, butyrate and glucose, respectively. The change of surface charge for the first two sludges was mainly due to the increase of proteinaceous fraction of ECP; but, for glucose-degrading sludge, that could be due to the increases of both proteinaceous and carbohydrate fractions of ECP. The negative-charged nature of anaerobic sludge implies that cations should be able to promote granulation of anaerobic sludge.

Modeling long term nutrient removal in a sequencing batch reactor

Abstract A modified version of IAWQ activated sludge model 2 (ASM 2) was developed to address the long-term dynamic behavior of nutrients in a sequencing batch reactor (SBR) activated sludge process. Experimental data was obtained from a long-term experimental work carried out in a 100-l bench scale SBR. Changes in TOC, NH4-N, NO3-N, NO2-N and PO4-P could be reliably predicted after the model parameters were adapted to the SBR conditions. Better phosphorus dynamics were achieved by considering the sub-model of denitrification by phosphorus accumulating organisms (PAO). Long-term simulations were carried out with the calibrated model to investigate the behavior of N and PO4-P under disturbed loading conditions. After attaining sufficient biological phosphorus removal activities in the sludge, influent TOC concentration was stepwise decreased and increased for 5 weeks. The decrease in organic loading caused the deterioration of biological phosphorus removal with simultaneous increase in effluent NO3-N concentration. Subsequently increasing the organic loading restored the original effluent conditions. The model simulation predictions well match with the experimental results under disturbed organic loading conditions. The simulated results implied that the deteriorating phenomena of phosphorus removal can be explained by two mechanisms; poor P-uptake by PAO and washout of PAO itself.

Predominance of ammonia-oxidizing archaea on granular activated carbon used in a full-scale advanced drinking water treatment plant.

Ozonation followed by granular activated carbon (GAC) is one of the advanced drinking water treatments. During GAC treatment, ammonia can be oxidized by ammonia-oxidizing microorganisms associated with GAC. However, there is little information on the abundance and diversity of ammonia-oxidizing microorganisms on GAC. In this study, the nitrification activity of GAC and the settlement of ammonia-oxidizing archaea (AOA) and bacteria (AOB) in GAC were monitored at a new full-scale advanced drinking water treatment plant in Japan for 1 year after plant start-up. Prechlorination was implemented at the receiving well for the first 10 months of operation to treat ammonia in raw water. During this prechlorination period, levels of both AOA and AOB associated with GAC were below the quantification limit. After prechlorination was stopped, 10(5) copies g-dry(-1) of AOA amoA genes were detected within 3 weeks and the quantities ultimately reached 10(6)-10(7) copies g-dry(-1), while levels of AOB amoA genes still remained below the quantification limit. This observation indicates that AOA can settle in GAC rapidly without prechlorination. The nitrification activity of GAC increased concurrently with the settlement of AOA after prechlorination was stopped. Estimation of in situ cell-specific ammonia-oxidation activity for AOA on the assumption that only AOA and AOB determined can contribute to nitrification suggests that AOA may account for most of the ammonia-oxidation. However, further validation on AOB contribution is required.

Chemical properties, microbial respiration, and decomposition of coarse and fine particulate organic matter

Abstract Fine particulate organic matter (FPOM) plays a critical role in structuring and sustaining stream food webs by providing an essential resource for various organisms. Our goal was to elucidate FPOM dynamics by determining chemical properties, microbial respiration, and in situ decomposition rates of different FPOM fractions in relation to the parent coarse particulate organic matter (CPOM). FPOM (100–500 μm) of defined quality was produced by feeding 5 types of CPOM to shredding amphipods (Gammarus spp.): wood, filamentous green algae, and conditioned leaves of ash, alder, and oak. Feeding and defecation of Gammarus homogenized POM of the different origins in terms of proximate lignin and nutrient content. FPOM had higher lignin content (20.5–45.6%) than did parental CPOM (5.7–26.8%), whereas molar C:N decreased during the conversion of CPOM (12–109) to FPOM (10–34). Microbial respiration rates on leaf-derived FPOM were lower (0.13–0.45 mg O2 g−1 C h−1) compared to rates measured for parent CPOM (0.37–0.80 mg O2 g−1 C h−1). Furthermore, microbial decomposition over 2 mo in a stream was slower for leaf-derived FPOM (k < 0.0015/d) than for the parent CPOM (k = 0.0013–0.0049/d), and this pattern resulted in a positive correlation between rates of microbial respiration and decomposition. Overall, our data indicate that transformation of CPOM to FPOM has a homogenizing effect toward lower C quality, which, in turn, reduces microbial activity and decomposition rate.

Urban rainwater harvesting systems : research, implementation and future perspectives

While the practice of rainwater harvesting (RWH) can be traced back millennia, the degree of its modern implementation varies greatly across the world, often with systems that do not maximize potential benefits. With a global focus, the pertinent practical, theoretical and social aspects of RWH are reviewed in order to ascertain the state of the art. Avenues for future research are also identified. A major finding is that the degree of RWH systems implementation and the technology selection are strongly influenced by economic constraints and local regulations. Moreover, despite design protocols having been set up in many countries, recommendations are still often organized only with the objective of conserving water without considering other potential benefits associated with the multiple-purpose nature of RWH. It is suggested that future work on RWH addresses three priority challenges. Firstly, more empirical data on system operation is needed to allow improved modelling by taking into account multiple objectives of RWH systems. Secondly, maintenance aspects and how they may impact the quality of collected rainwater should be explored in the future as a way to increase confidence on rainwater use. Finally, research should be devoted to the understanding of how institutional and socio-political support can be best targeted to improve system efficacy and community acceptance.