Nancy G. Love

A New Planning and Design Paradigm to Achieve Sustainable Resource Recovery from Wastewater

To employ technologies that sustainably harvest resources from wastewater (for example struvite granules shown here), new perceptions and infrastructure planning and design processes are required.

Perspectives on anaerobic membrane bioreactor treatment of domestic wastewater: A critical review

Interest in increasing the sustainability of water management is leading to a reevaluation of domestic wastewater (DWW) treatment practices. A central goal is to reduce energy demands and environmental impacts while recovering resources. Anaerobic membrane bioreactors (AnMBRs) have the ability to produce a similar quality effluent to aerobic treatment, while generating useful energy and producing substantially less residuals. This review focuses on operational considerations that require further research to allow implementation of AnMBR DWW treatment. Specific topics include membrane fouling, the lower limits of hydraulic retention time and temperature allowing for adequate treatment, complications with methane recovery, and nutrient removal options. Based on the current literature, future research efforts should focus on increasing the likelihood of net energy recovery through advancements in fouling control and development of efficient methods for dissolved methane recovery. Furthermore, assessing the sustainability of AnMBR treatment requires establishment of a quantitative environmental and economic evaluation framework.

Nitrification in Drinking Water Systems

Nitrification is increasingly a concern in United States potable water distribution systems. This paper reviews research on nitrification as it relates to the ammonia levels and unique environments present in potable water distribution systems. Factors affecting nitrification occurrence, nitrification impacts on water quality and corrosion, and nitrification monitoring and control methods are emphasized. The potential role of nitrogen cycling via coupled microbial and electrochemical reactions is also described.

Elucidating the Relative Roles of Ammonia Oxidizing and Heterotrophic Bacteria during the Biotransformation of 17α-Ethinylestradiol and Trimethoprim

The biological fate of 17α-ethinylestradiol (EE2; 500 ng/L to 1 mg/L) and trimethoprim (TMP; 1 μg/L to 1 mg/L) was evaluated with flow through reactors containing an ammonia oxidizing bacterial (AOB) culture, two enriched heterotrophic cultures devoid of nitrifier activity, and nitrifying activated sludge (NAS) cultures. AOBs biotransformed EE2 but not TMP, whereas heterotrophs mineralized EE2, biotransformed TMP, and mineralized EE2-derived metabolites generated by AOBs. Kinetic bioassays showed that AOBs biotransformed EE2 five times faster than heterotrophs. The basal expression of heterotrophic dioxygenase enzymes was sufficient to achieve the high degree of transformation observed at EE2 and TMP concentrations ≤ 1 mg/L, and enhanced enzyme expression was not necessary. The importance of AOBs in removing EE2 and TMP was evaluated further by performing NAS experiments at lower feed concentrations (500-1000 ng/L). EE2 removal slowed markedly after AOBs were inhibited, while TMP removal was not affected by AOB inhibition. Two key EE2 metabolites formed by AOB and heterotrophic laboratory-scale chemostats were also found in independent laboratory-scale mixed culture bioreactors; one of these, sulfo-EE2, was largely resistant to further biodegradation. AOBs and heterotrophs may cooperatively enhance the reliability of treatment systems where efficient removal of EE2 is desired.

Navigating Wastewater Energy Recovery Strategies: A Life Cycle Comparison of Anaerobic Membrane Bioreactor and Conventional Treatment Systems with Anaerobic Digestion

The objective of this study was to evaluate emerging anaerobic membrane bioreactor (AnMBR) technology in comparison with conventional wastewater energy recovery technologies. Wastewater treatment process modeling and systems analyses were combined to evaluate the conditions under which AnMBR may produce more net energy and have lower life cycle environmental emissions than high rate activated sludge with anaerobic digestion (HRAS+AD), conventional activated sludge with anaerobic digestion (CAS+AD), and an aerobic membrane bioreactor with anaerobic digestion (AeMBR+AD). For medium strength domestic wastewater treatment under baseline assumptions at 15 °C, AnMBR recovered 49% more energy as biogas than HRAS+AD, the most energy positive conventional technology considered, but had significantly higher energy demands and environmental emissions. Global warming impacts associated with AnMBR were largely due to emissions of effluent dissolved methane. For high strength domestic wastewater treatment, AnMBR recovered 15% more net energy than HRAS+AD, and the environmental emissions gap between the two systems was reduced. Future developments of AnMBR technology in low energy fouling control, increased flux, and management of effluent methane emissions would make AnMBR competitive with HRAS+AD. Rapid advancements in AnMBR technology must continue to achieve its full economic and environmental potential as an energy recovery strategy for domestic wastewater.

Enhanced biodegradation of carbamazepine after UV/H2O2 advanced oxidation.

Carbamazepine is one of the most persistent pharmaceutical compounds in wastewater effluents due to its resistance to biodegradation-based conventional treatment. Advanced oxidation can efficiently degrade carbamazepine, but the toxicity and persistence of the oxidation products may be more relevant than the parent. This study sets out to determine whether the products of advanced oxidation of carbamazepine can be biotransformed and ultimately mineralized by developing a novel methodology to assess these sequential treatment processes. The methodology traces the transformation products of the (14)C-labeled carbamazepine during UV/hydrogen peroxide advanced oxidation and subsequent biotransformation by mixed, undefined cultures using liquid scintillation counting and liquid chromatography with radioactivity, mass spectrometry, and UV detectors. The results show that the oxidation byproducts of carbamazepine containing a hydroxyl or carbonyl group can be fully mineralized by a mixed bacterial inoculum. A tertiary treatment approach that includes oxidation and biotransformation has the potential to synergistically mineralize persistent pharmaceutical compounds in wastewater treatment plant effluents. The methodology developed for this study can be applied to assess the mineralization potential of other persistent organic contaminants.

The effect of cationic salt addition on the settling and dewatering properties of an industrial activated sludge

Cations have been found to influence the settling and dewatering properties of activated sludge, especially for industrial wastewaters in which very high concentrations of monovalent cations are often found. Because the cation content of wastewaters is often influenced by upstream processes, an understanding of the influence of various cations can be an important consideration in pinpointing operational problems in wastewater treatment plants. An industrial activated-sludge treatment plant was studied to determine whether variations in settling and dewatering properties of the mixed liquor and waste solids could be caused by changes in the cation content of the wastewater. Laboratory reactors received both return activated sludge and wastewater from the industrial treatment plant, and the feed was supplemented with either sodium (Na + ), potassium (K + ), or magnesium (Mg + ). It was found that when the monovalent-to-divalent (M:D) cation ratio on a milliequivalent basis was increased to greater than approximately 2:1 by either Na + or K + addition, dewatering properties became poorer and polymer conditioning requirements increased. The soluble protein content also increased as the mixed liquor M:D ratio increased, indicating release of biopolymer from the flocs. Magnesium addition at low doses caused a decrease in the dewatering rate, but at higher doses both the settling and dewatering properties of waste solids improved substantially. Conversely, when Na + and K + concentrations in the raw wastewater decreased significantly to less than 10 and 0.1 milliequivalents (meq), respectively, settling and dewatering properties improved substantially and addition of Mg 2+ did not improve conditions beyond those of the unamended control. Each of the cations studied caused unique changes in the properties of activated-sludge solids that could not be correlated with the M:D ratio, suggesting that some of the effects are not simply physical/chemical but may be physiological as well.

Chemical Inhibition of Nitrification in Activated Sludge

The aims of this work were to develop a high‐rate fluidized‐bed bioprocess for ferric sulfate production, to characterize biomass retainment, and to determine the phylogeny of the enrichment culture. After 7 months of continuous enrichment and air aeration at 37°C, the iron oxidation rate of 8.2 g Fe2+ L−1h−1 (4.5·10−12 g Fe2+ cell−1 h−1) was obtained at a hydraulic retention time (HRT) of 0.6 h. However, oxygen supply became the rate‐limiting factor. With gas mixture (99.5% O2 /0.5% CO2 (vol/vol)) aeration and HRT of 0.2 h, the iron oxidation rate was 26.4 g Fe2+ L−1h−1 (1.0·10−11 g Fe2+ cell−1 h−1). Leptospirillum sp. was predominant in the mesophilic fluidized‐bed reactor (FBR) enrichment culture as determined by fluorescent in situ hybridization, while Acidithiobacillus ferrooxidans was not detected. Denaturing gradient gel electrophoresis (DGGE) of the amplified partial 16S rDNA showed only three bands, indicating a simple microbial community. DGGE fragment excision and sequencing showed that the populations were related to L. ferriphilum (100% similarity in sequence) and possibly to the genus Ferroplasma (96% similarity to F. acidiphilum). Jarosite precipitates accumulated on the top of the activated carbon biomass carrier material, increasing the rate of iron oxidation. The activated carbon carrier material, jarosite precipitates, and reactor liquid contained 59% (or 3.71·109 cells g−1), 31% (or 3.12·1010 cells g−1) and 10% (or 1.24·108 cells mL−1) of the total FBR microbes, respectively, demonstrating that the jarosite precipitates played an important role in the FBR biomass retainment.

The role of effluent nitrate in trace organic chemical oxidation during UV disinfection

Most conventional biological treatment wastewater treatment plants (WWTPs) contain nitrate in the effluent. Nitrate undergoes photolysis when irradiated with ultraviolet (UV) light in the 200-240 and 300-325 nm wavelength range. In the process of nitrate photolysis, nitrite and hydroxyl radicals are produced. Medium pressure mercury lamps emitting a polychromatic UV spectrum including irradiation below 240 nm are becoming more common for wastewater disinfection. Therefore, nitrified effluent irradiated with polychromatic UV could effectively become a de facto advanced oxidation (hydroxyl radical) treatment process. UV-based advanced oxidation processes commonly rely on addition of hydrogen peroxide in the presence of UV irradiation for production of hydroxyl radicals. This study compares the steady-state concentration of hydroxyl radicals produced by nitrate contained in a conventional WWTP effluent to that produced by typical concentrations of hydrogen peroxide used for advanced oxidation treatment of water. The quantum yield of hydroxyl radical production from nitrate by all pathways was calculated to be 0.24 ± 0.03, and the quantum yield of hydroxyl radicals from nitrite was calculated to be 0.65 ± 0.06. A model was developed that would estimate production of hydroxyl radicals directly from nitrate and water quality parameters. In effluents with >5 mg-N/L of nitrate, the concentration of hydroxyl radicals is comparable to that produced by addition of 10 mg/L of H(2)O(2). Nitrifying wastewater treatment plants utilizing polychromatic UV systems at disinfection dose levels can be expected to achieve up to 30% degradation of some micropollutants by hydroxyl radical oxidation. Increasing UV fluence to levels used during advanced oxidation could achieve over 95% degradation of some compounds.

Effluent organic nitrogen (EON): bioavailability and photochemical and salinity-mediated release.

The goal of this study was to investigate three potential ways that the soluble organic nitrogen (N) fraction of wastewater treatment plant (WWTP) effluents, termed effluent organic N (EON), could contribute to coastal eutrophication--direct biological removal, photochemical release of labile compounds, and salinity-mediated release of ammonium (NH4+). Effluents from two WWTPs were used in the experiments. For the bioassays, EON was added to water from four salinities (approximately 0 to 30) collected from the James River (VA) in August 2008, and then concentrations of N and phosphorus compounds were measured periodically over 48 h. Bioassay results, based on changes in DON concentrations, indicate that some fraction of the EON was removed and that the degree of EON removal varied between effluents and with salinity. Further, we caution that bioassay results should be interpreted within a broad context of detailed information on chemical characterization. EON from both WWTPs was also photoreactive, with labile NH4+ and dissolved primary amines released during exposure to sunlight. We also present the first data that demonstrate that when EON is exposed to higher salinities, increasing amounts of NH4+ are released, further facilitating EON use as effluent transits from freshwater through estuaries to the coast.