Tomohiro Tobino

Seawater-driven forward osmosis for enriching nitrogen and phosphorous in treated municipal wastewater: effect of membrane properties and feed solution chemistry.

Seawater-driven forward osmosis (FO) is considered to be a novel strategy to concentrate nutrients in treated municipal wastewater for further recovery as well as simultaneous discharge of highly purified wastewater into the sea with low cost. As a preliminary test, the performance of FO membranes in concentrating nutrients was investigated by both batch experiments and model simulation approaches. With synthetic seawater as the draw solution, the dissolved organic carbon, phosphate, and ammonia in the effluent from a membrane bioreactor (MBR) treating municipal wastewater were 2.3-fold, 2.3-fold, and 2.1-fold, respectively, concentrated by the FO process with approximately 57% of water reduction. Most of the dissolved components, including trace metals in the MBR effluent, were highly retained (>80%) in the feed side, indicating high water quality of permeate to be discharged. The effect of membrane properties on the nutrient enrichment performance was investigated by comparing three types of FO membranes. Interestingly, a polyamide membrane possessing a high negative charge demonstrated a poor capability of retaining ammonia, which was hypothesized because of an ion exchange-like mechanism across the membrane prompted by the high ionic concentration of the draw solution. A feed solution pH of 7 was demonstrated to be an optimum condition for improving the overall retention of nutrients, especially for ammonia because of the pH-dependent speciation of ammonia/ammonium forms. The modeling results showed that higher than 10-fold concentrations of ammonia and phosphate are achievable by seawater-driven FO with a draw solution to feed solution volume ratio of 2:1. The enriched municipal wastewater contains nitrogen and phosphorous concentrations comparable with typical animal wastewater and anaerobic digestion effluent, which are used for direct nutrient recovery.

Shotgun Isotope Array for Rapid, Substrate-Specific Detection of Microorganisms in a Microbial Community†

ABSTRACT The shotgun isotope array method has been proposed to be an effective new tool for use in substrate-specific microbe exploration without any prior knowledge of the community composition. Proof of concept was demonstrated by detection of acetate-degrading microorganisms in activated sludge and further verified by independent stable isotope probing (SIP).

Application of cDNA-AFLP to biomarker exploration in a non-model species Grandidierella japonica

Biomarkers of exposure can be used to identify specific contaminants that are adversely affecting aquatic organisms. However, it remains prohibitively costly to investigate multiple novel biomarkers of exposure in a non-model species, despite the development of next-generation sequencing technology. In this study, we focused on the use of cDNA-amplified fragment length polymorphism (AFLP) as a cost-effective biomarker discovery tool to test whether it could identify biomarkers of exposure in the non-model amphipod species Grandidierella japonica. Loci were identified that were differentially expressed in amphipods exposed to reference chemicals (Cu, Zn, and nicotine) and to an environmental sample (road dust) at sublethal concentrations. Eight loci were shown to respond consistently to nicotine at different concentrations, but not to Cu or Zn. Some of the loci also responded to an environmental road dust sample containing nicotine. These findings suggest that loci identified using cDNA-AFLP could be used as biomarkers of nicotine exposure in environmental samples with complex matrices. Further studies with other organisms and toxicants are needed, but we have demonstrated that the use of cDNA-AFLP to identify biomarkers for ecotoxicological studies of non-model species is at least feasible.

Causes of highway road dust toxicity to an estuarine amphipod: Evaluating the effects of nicotine

Urban road dust can potentially have adverse effects on ecosystems if it is discharged into receiving waters. This study investigated the causes of highway road dust toxicity by performing sediment toxicity identification evaluation (TIE) tests with an estuarine amphipod, Grandidierella japonica. In addition to metals and polycyclic aromatic hydrocarbons, which are traditionally considered to be the major toxicants in road runoff, we focused on dissolved nicotine as a causative toxicant. The sediment TIE results suggested that organic contaminants contributed to the majority of toxicity, and that the contribution of unionized nicotine to the toxicity was the highest among the chemicals considered. However, additional mortality tests with 48-h pulsed nicotine exposure demonstrated that exposure to nicotine at the same concentration as the baseline level in TIE tests did not cause significant 10-day amphipod mortality. Thus, the road dust toxicity could not be explained only by unionized nicotine, thereby suggesting contributions from joint effects of the measured toxicants and the presence of other unmeasured factors.

Development of a chronic sediment toxicity test using the benthic ostracod Heterocypris incongruens and their application to toxicity assessments of urban road dust

This study reports on the development and application of a chronic sediment toxicity test using the benthic ostracod Heterocypris incongruens. H. incongruens reproduction parameters such as egg production, first day of brooding, egg-laying ratio, and hatching ratio were examined in this study. The test was first validated by determining the repeatability of the test method under seven control performances. The results showed good test repeatability of most endpoints, with coefficient of variation (CV) results below 15%. However, lifetime egg production, hatching ratio, and the reproductive rate were highly variable, with CVs ranging from 29.5% to 51.9%. Next, an application example of the proposed chronic method was performed using a series of urban road dust (URD) samples diluted with a reference sediment and compared to a 6 d H. incongruens toxicity test. The results of the proposed chronic test showed a statistically significant difference in the first day of brooding at 6.25% URD which did not exhibit significant mortality and growth inhibition in 6 d toxicity test.

A Microcosm Study of Surface Sediment Environmental DNA: Decay Observation, Abundance Estimation, and Fragment Length Comparison

Interpretation of environmental DNA (eDNA) is a major problem hindering the application of this emerging technology for environmental monitoring. The decay characteristics and bioabundance estimation of different DNA fragment lengths are largely unknown, especially for eDNA captured from surface sediments. An estuarine amphipod, Grandidierella japonica, was used as the target species in this study. We conducted a lab-scale experiment using DNA extraction to clarify the effect of bacteria on eDNA decay. We also conducted a microcosm experiment using amphipods to clarify interpretations of information regarding eDNA decay and bioabundance estimation by using two fragments with different lengths (126 and 358 bp). It was found that the bacteria concentration accelerated eDNA decay, and long fragments were more susceptible to bacteria, thus decaying faster, than short fragments in the exponential decay period. The fresh eDNA (collected within 24 h of removing the amphipods) was more indicative of bioabundance than old eDNA (collected 240-480 h after removing amphipods), and short fragments better reflected bioabundance than long fragments. Finally, we compared the half-life of eDNA in surface sediment with that in a water sample and found that the temporal scales of surface sediment and water are similar (days to weeks). Our results suggest that surface sediment also has the potential to monitor the environment at a temporal scale similar to water.

Duration of life‐cycle toxicity tests with the ostracod Heterocypris incongruens

An acute sediment toxicity test using the ostracod Heterocypris incongruens is user friendly and has high sensitivity; however, a life-cycle test using this species has not been developed. The most challenging problem when developing a life-cycle test is that the egg development time varies greatly and is sometimes too long (> 150 d) to monitor. It is desirable to shorten the duration of life-cycle toxicity tests including the observation period of egg development while preserving the ecological relevance of the net reproductive rate (R0 ), an endpoint in the life-cycle test. Therefore, in the present study, we suggest a practical test duration for R0 using population growth rate (λ) as a measure of ecological relevance. We collected a range of life history characteristics of the ostracod by combining data from the literature and experimental results, constructed population matrix models, and calculated λ for 20 life history patterns. The results showed that a longer test period (> 150 d) did not increase the correlation coefficients between R0 and λ. Rather, a shorter test duration resulted in R0 being highly correlated with λ. Our results suggest that a life-cycle toxicity test using the ostracod can provide an ecologically relevant toxicity endpoint, even if the test is abandoned after approximately 50 d and unhatched eggs remain. Environ Toxicol Chem 2017;36:3443-3449.