Several compositions of Fenton's Reagent and hydrogen peroxide alone were used to disinfect combined sewage samples from a wastewater treatment facility. The presettled samples contained suspended solids (SS) and dissolved organic carbon (DOC) at concentrations of 28 and 290 mg/L, respectively. Disinfection with Fenton's Reagent was carried out at a pH between 5.90 and 6.0 and at a temperature of 25 • C. All disinfected samples contained residual oxidants. Under all reaction conditions studied, complete inactivation of E. coli was achieved within one minute of the addition of Fenton's Reagent. Disinfection with hydrogen peroxide alone under similar conditions is incomplete even under much longer contact times. O
We report unusually high nitrification activities at very low dissolved oxygen concentrations in a full-scale membrane bioreactor that operates with simultaneous nitrification denitrification and phosphorus removal, SNDP. We obtained a high affinity for oxygen in a nitrifying mixed culture population.. The calculated value for the half oxygen saturation coefficient was 0.01 mg/l, an order of magnitude lower than previously reported. This is the second independent report of these observations in full scale plants. We observed a seasonal reduction in the low dissolved oxygen nitrification activity that impacts the observed half saturation constant for oxygen for nitrification. We quantified the microbial population of nitrifiers in the system using molecular techmiques (qPCR) and observed that ammonia oxidizing archaea, AOA, were the dominant population. Anammox spcs were present but in insignificant numbers. Ammonia oxidizing bacteria, AOB, increase in numbers during the winter time consitently with the decrease in low DO nitrification activity. We observed that partial denitrification was the dominant path for simultaneous nitrification denitrification in the system. The most likely source of electrons for nitrification is endogenous substrate..This allows significant savings in the amount of oxygen and carbon that is required for biological nutrient removal enabling energy efficient strategies for wastewater treatment. We calculated that energy self-sufficiency is a viable option combining SNDP with a pretreatment process that routes BOD away from the BNR process to produce methane.
Stormwater best management practices (BMPs) require regular maintenance. The impact on trace metal concentrations in a constructed stormwater wetland BMP on Staten Island, New York, was investigated by analyzing sediment concentrations and tissue residues of the dominant macroinvertebrates (Tubifex tuhifex) prior and subsequent to maintenance. Trace metal concentrations were assessed using standard serial extraction (for sediment) and acid digestion (for tissue burdens) techniques, followed by quantitative determination using graphite furnace atomic absorption spectrometry and inductively coupled plasma optical emission spectrometry, respectively. The results suggest that disturbance of sediment during maintenance of the BMP resulted in an increase in the most mobile fraction of trace metals, especially those associated with finer grained sediments (< 63 |im), and as a consequence, measured metal concentrations in macroinvertebrates increased. Regressions of a subset of metal concentrations (copper, lead, and zinc) in sediment and the macroinvertebrate tissue burden samples generally increased as a result of maintenance. A follow-up sampling event 9 months after maintenance demonstrated that the most readily available form of trace metal in the BMP was reduced, which supports (1) long-term sequestration of metals in the BMP and (2) that elevated bioavailability following maintenance was potentially a transient feature of the disturbance. This study suggests that in the long-term, performing sediment removal might help reduce bioavailability of trace metal concentrations in both the BMP and the receiving water to which a BMP discharges. However, alternative practices might need to be implemented to reduce trace metal bioavailability in the short-term. Water Environ. Res., 84, 370 (2012).
The sources of heavy metals in urban stormwater runoff are diverse (e.g., highways, road surfaces, roofs) and the release of metals into the environment is governed by several complex mechanisms. Heavy metals in stormwater are associated with suspended particulate materials that vary from coarse (>75 µm) and fine particulates (<75 to 1 µm), to colloids (<1µm). Stormwater runoff investigations increasingly focus on evaluating quality and the effectiveness of adopting best management practices (BMPs) to minimize pollutant input, including heavy metals, to receiving waters. Heavy metals in stormwater are primarily removed by sedimentation in BMPs such as retention ponds and constructed wetlands; these sediments may be toxic to benthic invertebrates and aquatic microorganisms. Information on heavy metalsparticulate association is therefore a fundamental requirement prior to using wetland and pond BMPs for treatability studies. Research is being conducted at the U.S. EPA's Urban Watershed Research Facility in Edison, NJ to evaluate the effectiveness of retention pond and constructed wetland BMP mesocosms to remove particulate-bound heavy metals from roof and parking-lot stormwater runoff. The research objectives include: (i) investigating the association of selected heavy metals (Al, Cr, Cu, Fe, Mn, Pb, and Zn) with fine particulates (20 to 0.4 µm) in stormwater runoff; (ii) evaluating the relative removal of particulate-bound as well as dissolved heavy metals in retention ponds and cattail-wetland mesocosms; and, (iii) investigating the solidphase chemical associations of heavy metals in cattail wetland sediments and assessing the potential for sediment toxicity and heavy metal bioavailability. This investigation comprises the study of eight separate storm events; six sampling events have been completed to date. Preliminary results show that Al, Cr, Fe, and Pb are primarily particulate-bound (>20 µm) and Mn is mostly soluble. Cu and Zn are primarily associated with fine particulates (10 to 1 µm) and the dissolved fraction (<0.4 µm) in stormwater runoff. Also, the retention pond and cattail wetland mesocosms are effective in attenuating heavy metals, especially, Cu, Zn, Al, Cr, and Pb. Preliminary results are also presented for the chemical fractionation of cattail wetland sediments.
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