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In order to assess the microbial water quality of the lagoon canals of Venice, Italy and nearby beach on Lido island, a study was conducted using real-time RT-PCR to enumerate levels of hepatitis A virus (HAV) and enteroviruses in these marine waters over a 3-year period from 2003 to 2005. A total of 17 sites (9 lagoon canal and 8 beach sites) were assayed. For the canals of the Venice Lagoon, 78% were positive for both HAV and enteroviruses, with levels ranging from 75 to 730 and 3 to 1,614 genome copies/L, respectively. At Lido beach, HAV was never detected, but enteroviruses were detected in all Lido beach samples at levels ranging from 2 to 71 genome copies/L. There was a statistically significant correlation between thermotolerant coliform densities and HAV levels (p=0.0002), but the relationship between thermotolerant coliform densities and enterovirus levels was not significant (p>0.05). Despite the fact that enteroviruses were detected at low levels in the surfzone at Lido beach, the risk for enteroviral infection (calculated using the beta-Poisson model) for recreational exposure from swimming, was in the range of 1.9 x 10(-3) - 6.1 x 10(-2), yielding a disease risk at or below the level (5% for gastroenteritis) deemed acceptable by European Guide standards.

Biomonitoring of toxicity, using the Ceriodaphnia dubia acute toxicity test, was performed on a gasoline-contaminated aquifer in San Diego, Calif. undergoing in situ bioremediation. The bioremediation approach here featured nitrate enrichment of extracted groundwater (with subsequent reinfiltration back into the aquifer) to stimulate bacterial denitrification. Dentrification has been shown to support biodegradation of the monoaromatic hydrocarbons—benzene, toluene, ethylbenzene, and the isomers of xylene (BTEX). During the period between the start of bioremediation (October, 1989) and the end of nutrient enrichment (March, 1992), BTEX levels at the two most contaminated wells on site (MW1 and MW5) were reducted by about 81 and 99%, respectively. In acute bioassays of groundwater from MW1 during the first 6 months of bioremediation, concentrations of groundwater from about 3 to 10% produced 50% mortality of Ceriodaphnia after 24 h exposure, whereas groundwater concentrations of greater than 20% were required after remediation. When the 24-h LC50's for mortality were plotted as a function of BTEX concentration, the slope of the regression line was similar for both laboratory and field nitrate-enrichment studies. At MW5, where the BTEX level was dramatically reduced by 99% during bioremediation, the 24-h LC50 after bioremediation increased to 56% (from initial values of 12–15%), while uncontaminated groundwater from a well up-gradient of the gasoline leak, showed an LC50 value of 74%. These results demonstrate that even after bioremediation of an aquifer (with an associated BTEX reduction of 81–99%), the toxicity (as measured by Ceriodaphnia ) of the groundwaters may not be reduced to precontamination levels.

This report describes investigations using artificial wetlands which quantitatively assess the role of each of three higher aquatic plant types, Scirpus validus (bulrush), Phragmites communis (common reed) and Typha latifola (cattail), in the removal of nitrogen (via sequential nitrification-denitrification), BOD and TSS from primary municipal wastewaters. During the period August 1983–December 1984, the mean ammonia concentration of 24.7 mg l−1 in the primary wastewater inflow (hydraulic application rate = 4.7 cm day−1) was reduced to mean effluent levels of 1.4 mg l−1 for the bulrush bed, 5.3 mg l−1 for the reed bed and 17.7 mg l−1 for the cattail bed, as compared to a mean value of 22.1 mg l−1 for the unvegetated (control) bed. For all three vegetated beds, the mean effluent ammonia values were significantly below that for the unvegetated bed and for the inflow. The bulrushes and reeds (in that order) proved to be superior at removing ammonia, both with mean effluent levels significantly below that for the cattail bed. The high ammonia-N (and total N) removal efficiencies shown by the bulrush and reed beds are attributed to the ability of these plants to translocate O2 from the shoots to the roots. The oxidized rhizosphere so formed stimulates sequential nitrification-denitrification. Similarly BOD removal efficiencies were highest in the bulrush and reed beds, both with mean effluent BOD levels (5.3 and 22.2 mg l−1, respectively) significantly below that for the unvegetated bed (36.4 mg l−1) and equal to or better than secondary treatment quality (30 mg l−1). Our results demonstrate that higher aquatic plants can indeed play a significant role in secondary and advanced (N removal) wastewater treatment by wetland systems, a role that is completely distinct from that associated with their pollutant uptake capacity.

This report describes investigations which have demonstrated the exceptional utility of artificial wetlands for the removal of nitrate from secondary wastewater effluents at relatively high application rates. The artificial wetlands (14 in number) were plastic-lined excavations containing emergent vegetation growing in gravel. Without supplemental additions of carbon, total nitrogen removal efficiency was low (∼ 25%) in both vegetated and unvegetated beds. When methanol was added to supplement the carbon supply and stimulate bacterial denitrification, the removal efficiency was extremely high (95% removal of total nitrogen at a wastewater application rate of 16.8 cm day−1). Since methanol is a relatively expensive form of carbon, we tested the feasibility of using plant biomass, mulched and applied to the surface of marsh beds, as an alternate source of carbon. At a wastewater application rate of 8.4 cm day−1, the mean total nitrogen removal efficiency for the mulch-amended beds was 86%. When the application rate was higher (16.8 cm day−1) the mean total nitrogen removal efficiency was lower, 60% in the mulch-amended beds. By using plant biomass as a substitute for methanol, the energy savings for a treatment facility serving a small community (3785 m3 day−1 or 1 mgd) would amount to the equivalent of 731 day−1 of methanol. As the cost of fossil fuel increases, energy cost will become a predominant factor in the selection of small (0.5–5 mgd) wastewater treatment systems. However, in many cases where natural wetlands are either geographically unavailable or protected from wastewater discharge by environmental, legal, or aesthetic restraints, artificial wetlands offer a viable alternative for energy-effective treatment of municipal and agricultural wastewater effluents.

The CCBA process, which uses clay as an adsorbent followed by alum flocculation and clarification, was tested for its capability to remove viruses and turbidity so that subsequent sand filtration and disinfection could produce renovated wastewaters meeting reclamation criteria specified in Title 22 of the California Administrative Code. Both human poliovirus type 2 (Sabin vaccine strain) and MS2 bacteriophage (an F-specific RNA phage) were seeded into raw municipal wastewaters in bench-scale tests (500 ml) of the CCBA process. Plaque assays were performed to enumerate these viruses in effluents after basic CCBA treatment, after sand filtration and after disinfection by either combined chlorine residual, free chlorine residual or chlorine dioxide (ClO 2 ). The basic CCBA process followed by sand filtration removed 3.8 logs of poliovirus and 2.8 logs of MS2, and produced an effluent with a mean turbidity of less than 2 NTU. Using combined chlorine for disinfection, MS2 was reduced by greater than 4.3 logs (99.995%), while poliovirus was reduced either to undetectable levels, or when detected, reduced at least 6.1 logs. Using free chlorine or ClO 2 , both MS2 and poliovirus were reduced to undetectable levels when the effluent turbidity was below 2 NTU before disinfection.