Virus, phosphorus, and nitrogen removal in onsite wastewater treatment processes

Onsite wastewater treatment systems were operated at the UC Davis wastewater treatment facility for investigation of the fate of indigenous coliphage, nitrogen, and phosphorus in these systems. The treatment systems were selected because of their high efficiency and role in the future of onsite wastewater treatment. The treatment systems included (a) three high porosity, high surface area multi-pass biofilm reactors, (b) two submerged aerated biofilm reactors; one was inoculated with specific bacteria (i.e., bioaugmentation) for enhanced performance, and (c) a traditional septic tank followed by sand infiltration beds. In addition, soil basins were used to further evaluate the fate of contaminants after discharge from a treatment process to the environment. The septic tanks were found to remove less than 12.5 to 23.4 percent of nitrogen, 0 to 6.7 percent of phosphate, and 16.5 to 25.3 percent of virus, from the influent. The textile biofilters were found to remove 35.2 percent of nitrogen, no phosphorus, and 82 percent of virus from septic tank effluent. The sand beds were found to remove 12.8 percent of nitrogen, no phosphorus, and 96.4 percent of virus. After installation of the aeration systems, the sand bed performance improved for all parameters measured. In the soil infiltration system, all virus were removed and nitrogen and phosphorus were reduced to concentrations of 2 mg/L after passing through 30 in of Yolo loam soil

Providing reliable supply of safe drinking water poses challenges

Chlorination of drinking water has eradicated most waterborne disease epidemics. However, small water-supply systems struggle to maintain water quality and aging water-distribution systems are prone to contamination. By the year 2025, California's projected population of 48 million will demand between 1 trillion and 5 trillion gallons per year. Municipal demands clearly will exceed the currently available supply of tap water, forcing conservation and reuse. Future regulations are expected to focus on the quality of the water flowing from the user's tap, rather than the quality exiting the water-treatment facility. As little as 16% of the water treated and conforming to drinking-water health standards is likely to come into direct contact with humans, such as for bathing and drinking. Development of dual water-distribution systems would separate water destined for human consumption from that destined for firefighting, toilet flushing and other domestic uses. As industry manufactures new compounds for drugs, antibiotics, household products and so on, water treatment must be modified to remove or neutralize these new contaminants. Monitoring for new and chlorine-resistant pathogens is also needed

Anoxic treatment wetlands for denitrification

Anoxic subsurface flow (SSF) constructed wetlands were evaluated for denitrification using nitrified wastewater. The treatment wetlands utilized a readily available organic woodchip-media packing to create the anoxic conditions. After 2 years in operation, nitrate removal was found to be best described by first-order kinetics. Removal rate constants at 20°C (k20) were determined to be 1.41–1.30 d−1, with temperature coefficients (θ) of 1.10 and 1.17, for planted and unplanted experimental woodchip-media SSF wetlands, respectively. First-order removal rate constants decreased as length of operation increased; however, a longer-term study is needed to establish the steady-state values. The hydraulic conductivity in the planted woodchip-media SSF wetlands, 0.13–0.15 m/s, was similar to that measured in an unplanted gravel-media SSF control system

Nitrate in Potable Water Supplies: Alternative Management Strategies

<div><p>Nitrate contamination of drinking water sources has become one of the most important water quality concerns across the United States. Nitrate presents unique water treatment challenges and small water systems are particularly affected by the high costs of addressing nitrate impacted supplies. The goal of this investigation was to provide an overview of nitrate treatment options, highlighting the most recent advances and elucidating costs and common problems in application. No single treatment option is ideal for all situations; new technologies continue to be investigated to effectively remove nitrate while limiting cost and maximizing sustainability.</p></div