Multiple lines of evidence to identify sewage as the cause of water quality impairment in an urbanized tropical watershed.

Indicator bacteria, which are conventionally used to evaluate recreational water quality, can originate from various non-human enteric and extra-enteric sources, hence they may not be indicative of human health risk nor do they provide information on the sources of contamination. In this study we utilized traditional (enterococci and Escherichia coli) and alternative (Clostridium perfringens) indicator bacteria, F+-specific coliphage, molecular markers for microorganisms associated with human sewage (human-associated Bacteroides and polyomaviruses), and microbial community analysis tools (16S rRNA gene fragment amplicon sequencing), to identify and evaluate human sewage-related impact in the Manoa watershed in Honolulu, Hawaii. Elevated concentrations of enterococci (geometric mean ranging from 1604 to 2575 CFU 100 mL-1) and C. perfringens (45-77 CFU 100 mL-1) indicated impairment of the urbanized section of the stream, while indicator bacteria concentrations decreased downstream in the tidally influenced Ala Wai Canal. The threshold values triggering water quality violation notifications in Hawaii were exceeded in 33.3-75.0% of samples collected at sites in the urbanized section of Manoa Stream, but were not exceeded in any of the samples collected at an upstream site located in a forested area. Correlation between indicator bacteria concentrations and rainfall amounts was weak to moderate but significant (E. coli R = 0.251, P = 0.009; enterococci R = 0.369, P < 0.001; C. perfringens R = 0.343, P < 0.001), while concentrations of human fecal-associated molecular markers were not significantly correlated with rainfall (human-associated Bacteroides, R = 0.131, P = 0.256; human-associated polyomaviruses, R = 0.213, P = 0.464). Presence of human sewage was confirmed by detection of human-associated Bacteroides and human polyomavirus in the urbanized section of Manoa Stream (83.3-100% and 41.7-66.7% positive samples respectively). It was further confirmed by microbial community analyses which suggested that an average 2.4-3.4% of the total bacterial population in this section was associated with sewage. Microbial community profiles were significantly influenced by rainfall (R2 = 0.4390, P < 0.001), pH (R2 = 0.3077, P = 0.006), salinity (R2 = 0.2614, P = 0.038), and conductivity (R2 = 0.2676, P = 0.031). Although microbial diversity fluctuated throughout the watershed, it was lower in the impaired section. Leaking sewer systems and illegal cross-connections are implicated in the impairment of the watershed, hence both the sewer and the storm water lines should be routinely inspected. Collectively, our data suggest that information derived from the analysis of microbial communities complements current marker-based microbial source tracking techniques and environmental monitoring programs.

Pharmaceutically active compounds: Their removal during slow sand filtration and their impact on slow sand filtration bacterial removal.

Slow sand filtration (SSF) has been widely used as a means of providing potable water due to its efficacy, low cost, and minimal maintenance. Advances in analytical instrumentation have revealed the occurrence of pharmaceutically active compounds (PhACs) in surface water as well as in groundwater. It is unclear if the presence of these compounds in the feed water can interfere with the performances of an SSF unit. The aim of this work was to examine i) the ability of two SSF units to remove six PhACs (caffeine, carbamazepine, 17-ß estradiol [E2], estrone [E1], gemfibrozil, and phenazone), and ii) the impact of these PhACs on the removal of bacteria by two SSF units. The presence of PhACs in feed water for SSF can occur in surface waters impacted by wastewater or leakage from sewers and septic tanks, as well as in developing countries where unregulated use and improper disposal are prevalent. Two pilot-scale SSF units were used during the study. Unit B1 was fed with stream water with 1% of primary effluent added, while unit B2 was fed with stream water alone. Although limited removal (<10%) of carbamazepine, gemfibrozil, and phenazone occurred, the complete removal of caffeine, and the partial removal (11-92%) of E2 and E1 were observed in the two SSF units. The results of this study suggest that the occurrence of the selected PhACs, probably estrogens and caffeine, in the feed water at 50 µg L(-1) affected the ability of the schmutzdecke to remove total coliform and Escherichia coli. The bacterial removal achieved within the schmutzdecke dropped from 95% to less than 20% by the end of the study. This decrease in removal may be related to the change in the microbial community within the schmutzdecke. A diverse microbial community, including Bacteroidetes and several classes of Proteobacteria, was replaced by a microbial community in which Gammaproteobacteria was the predominant phylum (99%). Despite the low removal achieved within the schmutzdecke, removal of total coliform and E. coli greater than 99% occurred after both SSF units throughout the study. Bacterial removal occurred in the upper half of the sand filter. This was probably due to a diverse microbial community established in the packing material, in which Bacteroidetes (13-25%), Acidobacteria (7-17%) and several classes of Proteobacteria (35-52%) (Alpha-, Beta-, Delta-, and Gammaproteobacteria) were the predominant phyla.

Fate of selected pharmaceutically active compounds during simulated riverbank filtration.

The objective of this study was to investigate the effect of temperature, oxygen, and organic matter on the removal of selected pharmaceutically active compounds (PhACs) during simulated riverbank filtration (RBF). The behavior of six PhACs (caffeine, carbamazepine, 17-ß estradiol [E2], estrone [E1], gemfibrozil, and phenazone) was evaluated by small flow-through column experiments. Results from our study showed that RBF can be used to treat many of the PhACs found in environmental waters. Local conditions at the RBF site, however, can affect the removal of PhACs and should be investigated. Biodegradation and sorption represented the predominant mechanisms involved during the removal of the selected PhACs. All selected PhACs showed limited and slower removal during the winter. Phenazone was highly impacted by the level of oxygen; complete depletion of phenazone below the analytical limit occurred only under aerobic conditions (dissolved oxygen >8 mg L(-1)). Caffeine and E2 were highly impacted by the presence of humic acid in the feed water. Caffeine and E2 were depleted below the detection limit in the presence of humic acid regardless of the temperature and the level of oxygen. E1 was impacted by the different environmental conditions and depletion below the detection limit occurred only during the summer under aerobic conditions. Carbamazepine (10%) and gemfibrozil (<30%) showed limited removal regardless of the different levels of temperature, oxygen and humic acid.

An evaluation of the mobility of pathogen indicators, Escherichia coli and bacteriophage MS-2, in a highly weathered tropical soil under unsaturated conditions.

Laboratory column experiments were conducted to study the effects of anionic polyacrylamide (PAM) polymer and surfactant linear alkylbenzene sulfonate (LAS) on the movement of Escherichia coli and the FRNA phage MS-2. The study was designed to evaluate if PAM or PAM + LAS would enhance the mobility of human pathogens in tropical soils under unsaturated conditions. No breakthrough of phage was observed in a 10 cm column after passing 100 pore volumes of solution containing 1x10(8) plaque-forming units (PFU)/ml. In later experiments, after passing 10-20 pore volumes of influent containing 1x10(8)/ml MS-2 or E. coli through 15 cm columns, the soil was sliced and the organisms eluted. Phage moved slightly deeper in the polymer-treated column than in the control column. There was no measurable difference in the movement of E. coli in either polymer-treated or control columns. The properties of the soil (high amounts of metal oxides, kaolinitic clay), unsaturated flow conditions, and relatively high ionic strengths of the leaching solution attributed to significant retention of these indicators. The impacts of PAM and LAS on the mobility of E. coli or MS-2 phage in the chosen soils were not significant.