Browsing by Subject "Water reuse"

Now showing 1 - 5 of 5

Evaluation of two water reuse applications : cooling tower makeup water and residential HVAC condensate reuse
(2016-12-02) Reuter, Samantha Jean; Kinney, Kerry A.; Katz, Lynn Ellen
This study evaluated the potential impacts of two water reuse applications – urban cooling towers and residential homes. Large water demands make cooling towers an attractive target for water reuse applications. However, poorly operated cooling towers have historically been linked to diseases such as Legionnaire’s Disease, and there is limited understanding on how transitioning from potable to alternative water sources will impact the microbial communities within cooling tower basins. Therefore, the microbial communities of three well-maintained and disinfected urban cooling towers were studied to assess the impact of source water on microbial populations, diversity, and the presence of potentially pathogenic organisms. Illumina sequencing results indicate that different makeup water sources do yield microbial basin communities that differ substantially in composition and diversity. Also, total bacterial loads in each basin decreased with increasing fraction of potable water used in the makeup water. Legionella spp. levels above 6 logGC/L were observed in a cooling tower basin that used reclaimed and potable water as makeup water sources. However, none of the basin or makeup water sources had quantifiable levels of L. pneumophila, indicating the Legionella present in the cooling towers was mostly non-pneumophila Legionella. Residential HVAC condensate was evaluated because it is a largely untapped water source that may be suitable for recovery and reuse. The two main challenges for HVAC condensate collection is estimating the condensate production volume and understanding the water chemistry of the condensate. Both production rate and water chemistry are crucial to understanding which reuse options are available for HVAC condensate. Thus, this study tested a method for estimating condensate production volumes and analyzed the water chemistry of condensate samples from three separate HVAC units at different residences. Measured condensate production volumes were within 12 to 25 percent of predicted values, and the water chemistry results identified the presence of both metals and organic species. Both studies indicate the importance of considering water quality for water reuse applications.
Freshwater on the island of Maui : system interactions, supply, and demand
(2011-05) Grubert, Emily; Webber, Michael E., 1971-; Passalacqua, Paola; King, Carey
This work is part of a broader, multi-year investigation of Maui Island’s freshwater resources. Maui Island faces multiple resource constraints, including water, land, energy, and capital, and these resource constraints could become relevant over the next forty years. Not only does Maui face potential changes to its water and other systems due to external factors beyond its control, like anthropogenic and other climate changes, but Maui also could make developmental choices that will impact how its resource systems interact. In particular, this work looks at Maui’s freshwater systems as they relate to energy, waste, and environmental systems. This report provides a foundation for future scenario analysis on the island that will aim to characterize potential synergies and hazards of choices like increased food production, local fuel production, and increased use of renewable energies.
Investigating the role of decentralized water systems as strategies for urban water and wastewater management
(2019-08-14) Berhanu, Bruk M.; Webber, Michael E., 1971-; Faust, Kasey M; Nagy, Gyorgy Z; Olmstead, Sheila M; Passalacqua, Paola
In the face of population growth and climate change impacts, water supply planners and utilities have increased interest in decentralized water systems as a means to meet potable water demands and improve water supply resilience in times of drought. Decentralized water systems (DWS) refer to technologies that capture, treat, and recycle alternative water supplies (rainwater/stormwater, graywater/blackwater, foundation drainage, air-conditioned condensate, etc.) to supply non-potable water for uses including toilet/urinal flushing, clothes washing, and irrigation on a building site. These systems offer benefits to individual users including water/wastewater rate savings, stormwater reductions, and resilience to water/wastewater service interruptions. Benefits can also extend to centralized water and wastewater networks by reducing water and wastewater treatment needs, preserving water supplies, and reducing net energy demands for water/wastewater treatment and delivery. However, these systems have not seen widespread adoption across the United States nor internationally. For utilities and water providers wishing to promote adoption of these technologies, little information is available regarded expected efficacy and cost metrics that can be used to design policies tailored for their service area. Moreover, current methods to assess these systems at-scale typically rely on assumptions of homogeneous single-family residential service areas and/or adoption rates that do not consider individual-level differences in land use characteristics, customer types, or adoption criteria. This research provides a framework by which to integrate these factors into assessments of decentralized water systems at the service area scale. The research is presented in three steps; an investigation into the drivers of indoor and outdoor water demands for residential and non-residential customers, integration of these demands via customer type into daily time-scale simulations of DWS performance under uncertainty, and application of psycho-social influences combined with technical and economic performance criteria to the decision to adopt DWS over long-range planning horizons. The non-residential sector has not seen the same level of investigation as the residential sector, and so a classification and statistical analysis model using mixed-effects linear regression was developed to relate parcel-level attributes such as industry type, conditioned area, and employment level to total monthly water demands. Results from this model suggest that parcel-level water demand differs most across industry classifications, while estimates for effect of parcel attributes on demand are more similar between classifications. Moreover, the predictor variables studied accounted for over 90% of variance seen in monthly demand values, after accounting for individual-level random effects. The results from the statistical analysis were then incorporated, along with residential demand estimates, into a daily water balance simulation model of DWS performance. Results suggest that tradeoffs exist between capital cost and cost-effectiveness of DWS adoption and technical performance via non-potable demand reductions. Hybrid rainwater-graywater systems and graywater for indoor and outdoor uses were both found to meet 100% of non-potable demand across uncertainty ranges in demands and alternative water supplies, though hybrid systems had higher capital costs primarily due to the need for a rainwater storage cistern. All systems incorporating graywater were capable of realizing net benefits under certainty conditions while solely rainwater based configurations almost never saw such outcomes. The results from the first and second analyses were then integrated into a hybrid agent-based and discrete-event sequence model to simulate adoption of DWS technologies by customers in a synthetically generated neighborhood. The model applies Systems-of-Systems analysis concepts to integrate individual-level decision making and behavior with aggregate-scale exogenous factors to understand how technical, economic, and psycho-social factors might affect adoptions rates of DWS and corresponding impacts to centralized water/wastewater infrastructure networks. Results suggest that non-residential customers are more heterogeneous in their adoption preference, with respect to DWS configuration, than the residential sector which primarily adopts graywater-based systems solely for outdoor use. Additionally, the tradeoff between capital cost and non-potable offsets for higher performing DWS configurations typically results in low adoption rates of these systems, but high per-system demand reductions that are commensurate with more widely adopted but lesser performing systems, such as sole rainwater for irrigation. These results highlight the importance of tailored DWS adoption decisions to adopter preferences and provide insight into possible policy instruments such as capital cost incentives, dual-reticulation mandates for new construction, and water demand offset requirements (without a technology prescription) that might promote adoption of these systems. When the results from these analyses are considered in context of a particular study area, this research provides a comprehensive set of methods by which to evaluate the opportunities for and potential impacts from parcel-level DWS adoptions from the perspectives of both the customer and the centralized water/wastewater service provider. Such a set of methods can be incorporated into long-range centralized water/wastewater infrastructure planning efforts to leverage the benefits of DWS adoption while managing the potential downsides
Membrane bioreactor treatment of household light greywater : measurement and effects of phosphorus limitation
(2013-05) Van Epps, Amanda Jane; Katz, Lynn Ellen; Speitel, Gerald E.
As water stresses increase across the U.S., interest in household water reuse is growing. Such reuse typically focuses on light greywater, that is all wastewater generated in the house excluding toilet waste and kitchen wastewater. As this practice becomes more widespread, higher level reuse is expected to require greater greywater treatment prior to reuse. Membrane bioreactors (MBRs) are an attractive technology for this application because they offer a robust combination of treatment processes and are already used in some households in countries such as Japan. This research sought to understand the role of phosphorus availability in determining the quality of effluent from MBR treatment of light greywater because phosphorus concentrations are expected to be low with phosphorus phased out of many consumer products. Less than 30 [mu]g/L of dissolved orthophosphate was present in synthetic greywater made from three common household products, and no measurable amount of dissolved orthophosphate was found in real greywater, but low concentrations of particulate phosphate were detected. These concentrations were well below levels believed necessary to achieve full BOD₅ removal in biological treatment. Nevertheless, MBR performance was not adversely affected until no supplemental phosphorus was provided. Measurement of extracellular enzyme activity showed an increase in the ratio of phosphatase activity to total glycosidase activity with declining phosphorus concentration, providing an early indication of nutrient stress before changes in effluent water quality were detected. Removal of three xenobiotic organic compounds (XOCs) in treatment of synthetic greywater was also evaluated under conditions of phosphorous limitation and balance. Abiotic removal mechanisms were not deemed to be important, but removal of methylparaben and sodium lauryl sulfate via biodegradation responded to nutrient limitation similarly to overall COD removal while removal of diethyl phthalate was affected to a greater extent. Measurement of plasmid DNA concentrations was evaluated as a potential indicator of the effect of nutrient limitation on plasmid-mediated biodegradation of XOCs. An overall reduction in the plasmid content was observed in all cases under conditions of phosphorus limitation; however, the extent of reduction was reactor dependent.
Residential water reclamation in Texas : can it work?
(2007-05) Dent, Kelly McCaughey; Butler, Kent S.
Although Texas is a water reclamation leader in the country for quantity of water reclaimed, it falls behind both California and Florida in residential applications. The concept of residential reuse has some barriers to overcome prior to implementation on a broad scale in Texas. The two case studies, St. Petersburg, Florida, and the El Dorado Irrigation District of El Dorado County, California, describe extensive reuse programs in response not only to impending water shortages but also to effluent disposal limitation requirements. Major factors that limit residential reuse in Texas include the following: cost, expediency and negative public perception. Two other considerations exist when determining the feasibility of implementing residential reuse: income level and irrigation needs. Most of the successful reuse programs examined were for higher income areas. Also, irrigation expectations and needs of the residences play a major factor in the success of the program. In arid environments planted with drought-tolerant plants, landscape irrigation becomes less of a priority. Further limitations that specifically affect Texas’ expanding its water reclamation programs include the legal issues of existing water rights and direct versus indirect reuse.