Four pathogenic virus removal mechanisms were investigated in a full-scale membrane bioreactor (MBR; nominal pore size 0.04 μm): (i) attachment of virus to mixed liquor solids; (ii) virus retention ...by a just backwashed membrane; (iii) virus retention by the membrane cake layer; and (iv) inactivation. We quantified adenovirus, norovirus genogroup II (GII), and F+ coliphage in the influent wastewater, the solid and liquid fractions of the mixed liquor, return flow, and permeate using quantitative PCR (adenovirus and norovirus GII) and infectivity assays (F+ coliphage). Permeate samples were collected 4–5 days, 1 day, 3 h, and immediately after chlorine enhanced backwashes. The MBR achieved high log removals for adenovirus (3.9 to 5.5), norovirus GII (4.6 to 5.7), and F+ coliphage (5.4 to 7.1). The greatest contribution to total removal was provided by the backwashed membrane, followed by inactivation, the cake layer, and attachment to solids. Increases in turbidity and particle counts after backwashes indicated potential breakthrough of particles, but virus removal following backwashes was still high. This study demonstrates the ability of the MBR process to provide over 4 logs of removal for adenovirus and norovirus GII, even after a partial loss of the cake layer, and provides evidence for assigning virus disinfection credit to similar MBRs used to reclaim wastewater for reuse.
This study provides an overview of established processes as well as recent progress in emerging technologies for advanced oxidation processes (AOPs). In addition to a discussion of major reaction ...mechanisms and formation of by-products, data on energy efficiency were collected in an extensive analysis of studies reported in the peer-reviewed literature enabling a critical comparison of various established and emerging AOPs based on electrical energy per order (EEO) values. Despite strong variations within reviewed EEO values, significant differences could be observed between three groups of AOPs: (1) O3 (often considered as AOP-like process), O3/H2O2, O3/UV, UV/H2O2, UV/persulfate, UV/chlorine, and electron beam represent median EEO values of <1 kWh/m3, while median energy consumption by (2) photo-Fenton, plasma, and electrolytic AOPs were significantly higher (EEO values in the range of 1–100 kWh/m3). (3) UV-based photocatalysis, ultrasound, and microwave-based AOPs are characterized by median values of >100 kWh/m3 and were therefore considered as not (yet) energy efficient AOPs. Specific evaluation of 147 data points for the UV/H2O2 process revealed strong effects of operational conditions on reported EEO values. Besides water type and quality, a major influence was observed for process capacity (lab-vs. pilot-vs. full-scale applications) and, in case of UV-based processes, of the lamp type. However, due to the contribution of other factors, correlation of EEO values with specific water quality parameters such as UV absorbance and dissolved organic carbon were not substantial. Also, correlations between EEO and compound reactivity with OH-radicals were not significant (photolytically active compounds were not considered). Based on these findings, recommendations regarding the use of the EEO concept, including the upscaling of laboratory results, were derived.
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•Short summary of radical generation mechanisms and application of AOPs.•First comparison of published EEO values across different AOPs.•Critical consideration of influencing factors on reported EEO values within UV/H2O2.•Proposal for proper use of the EEO-concept.•Discussion of major oxidation by-product formation mechanisms.
A Changing Framework for Urban Water Systems Hering, Janet G; Waite, T. David; Luthy, Richard G ...
Environmental science & technology,
10/2013, Letnik:
47, Številka:
19
Journal Article
Recenzirano
Odprti dostop
Urban water infrastructure and the institutions responsible for its management have gradually evolved over the past two centuries. Today, they are under increasing stress as water scarcity and a ...growing recognition of the importance of factors other than the cost of service provision are forcing a reexamination of long-held ideas. Research and development that supports new technological approaches and more effective management strategies are needed to ensure that the emerging framework for urban water systems will meet future societal needs.
•Three inocula have been tested systematically with four different substrates.•If inoculum’s origin impacts the performance in BMP test depend on the substrate.•Methane yield was not significantly ...influenced by the inoculum except for cellulose.•Degradation velocity was highest for the inoculum adapted to the substrate.
The impact of the inoculum’s origin on the methane yield in Biochemical Methane Potential (BMP) tests was investigated. The three most commonly applied inocula were chosen, originating from (i) a digester of a wastewater treatment plant, (ii) an agricultural biogas plant treating manure and energy crops, and (iii) a biowaste treatment plant. The performance of each inoculum was tested with four different substrates, namely sewage sludge, dried whole crop maize, food waste, and microcrystalline cellulose as a typical reference material. The results revealed that the choice of inoculum had no significant impact on the specific methane yield of the tested substrates except for cellulose. Still, the specific methane production rate was significantly influenced by the choice of the inoculum especially for sewage sludge, but also for food waste and cellulose, whereas it became clear that an inoculum adapted to a substrate is beneficial for a speedy digestion.
Wastewater treatment plants in many countries use anaerobic digesters for biosolids management and biogas generation. Opportunities exist to utilise the spare capacity of these digesters to co-digest ...food waste and sludge for energy recovery and a range of other economic and environmental benefits. This paper provides a critical perspective for full-scale implementation of co-digestion of food waste and wastewater sludge. Data compiled from full-scale facilities and the peer-reviewed literature revealed several key bottlenecks hindering full-scale implementation of co-digestion. Indeed, co-digestion applications remain concentrated mostly in countries or regions with favourable energy and waste management policies. Not all environmental benefits from waste diversion and resource recovery can be readily monetarised into revenue to support co-digestion projects. Our field surveys also revealed the important issue of inert impurities in food waste with significant implication to the planning, design, and operation of food waste processing and co-digestion plants. Other pertinent issues include regulatory uncertainty regarding gate fee, the lack of viable options for biogas utilisation, food waste collection and processing, impacts of co-digestion on biosolids reuse and downstream biogas utilisation, and lack of design and operation experience. Effort to address these bottlenecks and promote co-digestion requires a multi-disciplinary approach.
•Co-digestion of raw sludge and food waste was studied.•Results from batch trials were compared with full-scale experiences.•Mass balance of WWTP revealed a rise of 18% compared to batch tests.•Share ...of self-generated energy has more than doubled with 10% food waste.
The effects of co-digestion of food waste in a municipal wastewater treatment plant (WWTP) were studied in batch tests. The results obtained were compared with the mass balance of a digester at a full-scale WWTP for a one-year period without and with the addition of co-substrate. The specific methane yield calculated from the balance was 18% higher than the one in the batch tests, suggesting a stimulation of methane generation by co-digestion. It was hypothesized that this increase was caused by shifting the C/N ratio of raw sludge (8.8) to a more favourable ratio of the added food waste (17.7). In addition, potential benefits by adding food waste for energy autarky was investigated. While just 25% of the total energy demand of the plant could be recovered by biogas generation when no co-substrate was fed, this percentage has more than doubled when food waste was added at a ratio of 10% (w/w).
The discharge of wastewater effluents to a stream that is subsequently used for drinking water abstraction has been previously referred to as de facto water reuse. Where the abstraction of surface ...water for drinking water production occurs via induced bank filtration or aquifer recharge, additional site-specific factors should be considered to assess the impact of wastewater effluents on bank-filtered water. This study represents the first national reconnaissance to quantify wastewater effluent contributions in streams across Germany and consequences for indirect drinking water abstraction from these streams. An automated assessment using ArcGIS was conducted for river basins considering minimum and mean average discharge conditions of streams as well as discharge from more than 7500 wastewater facilities. In urban areas, where the natural base discharge is low, wastewater effluent contributions greater than 30–50% were determined under mean minimum discharge conditions, which commonly prevail from May to September. A conceptual model was proposed to estimate critical bank filtrate shares resulting in exceedances of monitoring trigger levels for health-relevant chemicals as a universal qualitative assessment regarding the relevance of de facto reuse conditions in surface waters used for drinking water abstraction. This approach was validated using chemical monitoring data for three case study locations.
Capacitive deionization (CDI) with carbon-aerogel electrodes represents a novel process in desalination of brackish water and has merit due to its low fouling/scaling potential, ambient operational ...conditions, electrostatic regeneration, and low voltage requirements. The objective of this study was to investigate the viability of CDI in treating brackish produced water and recovering iodide from the water. Laboratory- and pilot-scale experiments were conducted to identify ion selectivity, key operational parameters, evaluate desalination performance, and assess the challenges for its practical applications. The performance of the CDI technology (CDT®) system tested was consistent throughout the laboratory- and field-scale experiments. Deterioration of the carbon-aerogel electrodes was not observed during testing. The degree of ions adsorbed to the carbon aerogel (in mol/g aerogel) during treatment of brackish water was dependent upon initial ion concentrations in the feed water with the following selectivity I>Br>Ca>alkalinity>Mg>Na>Cl. The preferential sorption of iodide revealed merit to efficiently recover iodide from brackish water even in the presence of dominant co-ions. The research findings derived from this study identified parameters that merit further improvements regarding design and operation, including modification of pore-size distribution of aerogel, development of high capacitance and low-cost electrode materials, reducing the dead volume after regeneration and rinsing, minimizing energy consumption, and maximizing system recovery.
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