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This study examines the effect of pipe characteristics and stagnation time on nitrification, disinfectant loss, and organic carbon concentrations. Pipe racks consisting of different pipe materials (chlorinated polyvinyl chloride [CPVC], cross‐linked polyethylene [PEX‐B], and copper), diameters (0.75 and 0.5 in.), and water stagnation times (1 week and 12 hr) were set up in two cities with different disinfectants (chloramine and free chlorine) and different corrosion control (orthophosphate vs. pH/alkalinity adjustment). Copper pipe material had lower residual concentrations relative to plastic pipe in both water systems. In the chloramine system, residual concentrations were lower for smaller‐diameter pipes, whereas diameter did not strongly influence residual concentration in the chlorine system. Total organic carbon (TOC) increased during stagnation in the chloramine system. Nitrification was observed in the chloramine system for stagnation times of 1 week and 12 hr, indicating that flushing as frequently as every 12 hr may not be an effective mechanism for nitrification control in building plumbing. [ABSTRACT FROM AUTHOR]

Recent interest has arisen in the use of biochar as a low-cost adsorbent for control of organic micropollutants in water. However, compared with activated carbon (AC), biochar adsorption capacity is typically one to two orders of magnitude lower. This study reports batch mode adsorption of anionic (2,4-D, C0 100 μg/L) and neutral (simazine [SZN], C0 1.5 μg/L) herbicides from surface water containing dissolved organic matter at 4 mg/L total organic carbon concentration. Enhanced adsorption was observed by biochars generated from updraft gasifiers under conditions of simultaneous co-pyrolysis thermal air activation (CPTA). 2,4-D adsorption by ≥850°C CPTA biochars was more than 10 times greater on a mass basis compared with biochars generated from a conventional anoxic pyrolysis (CAP) reactor and was equivalent to AC reference adsorbents on a surface area normalized basis. Biochars generated at ≥850°C under CPTA conditions had similar micropore surface area to CAP biochars (∼330 m2/g) but about 2.5 times the mesopore surface area (∼110 m2/g CPTA, ∼40 m2/g CAP), suggestive of increased pore accessibility generated by thermochemical widening of pores and/or removal of pyrolysis tars by CPTA. 2,4-D adsorption from surface water was shown to correlate strongly with biochar H:C molar ratio within but not between biochars grouped by CAP and CPTA generation conditions. Comparing adsorption of 2,4-D and SZN by biochars generated from CAP and CPTA conditions suggested that herbicide interaction with biochar surface functional groups through formation of charge-assisted H-bonds did not play a significant role in herbicide uptake from surface water. [ABSTRACT FROM AUTHOR]

A scale-up methodology was developed and verified that utilizes bench-scale biofilter results to simulate field-scale (pilot or full scale), flow-through biofilter performance. This methodology builds on recirculating batch reactor methods combined with single-pass flow-through methods at empty bed contact times (EBCTs) equivalent to the field scale. This method allows for control of variables that are often not controllable at the field-scale level, that is, influent primary and secondary substrate concentrations, temperature, and replication. The robustness of the method was verified using dissolved organic carbon (DOC) removal in one drinking water (DW) and two wastewater (WW) effluents and the removal of 12 trace organic contaminants in one WW effluent. The average absolute difference (delta) between bench- and pilot-scale results for 14 comparisons was 2% for DOC removal. Experimental DOC results were not impacted by the range of biofilter hydraulic loading rates (HLRs) with a WW effluent and a DW effluent, confirming that at Damköhler number II values less than 0.1, the biofilters were reaction rate limited with little contribution from mass transfer. This allows for the use of lower HLRs and shorter filter media depths at the bench scale to yield equivalent EBCTs of field scale. Utilizing bioacclimated media, this bench-scale methodology could expedite biofilter implementation in DW and water reuse treatment plants. [ABSTRACT FROM AUTHOR]

The principal goal of this research was to develop a new scale-up procedure with which the adsorption of organic micropollutants (MPs) by granular activated carbon (GAC) can be predicted from bench-scale tests. To develop scale-up approaches, the adsorption of 29 environmentally relevant MPs was studied in both pilot-scale GAC adsorbers and rapid small-scale column tests that were based on the proportional diffusivity design (PD-RSSCT). Four surface waters with different dissolved organic carbon (DOC) concentrations were spiked with MPs at ng/L levels and tested in PD-RSSCTs simulating full-scale empty bed contact times of 7 and 15 min. Corresponding pilot-scale tests showed MP breakthrough occurred earlier than in PD-RSSCTs, and MP-specific differences between the PD-RSSCT and pilot column breakthrough curves were described by fouling parameters. On average, the PD-RSSCT overpredicted pilot-scale MP breakthrough by a factor of 3.0 ± 1.2 ( n = 101). Two approaches were developed for predicting bed volumes that can be treated to 10% MP breakthrough in full-scale adsorbers (BV10%,full-scale). In the first approach, a predictive relationship for the fouling parameter was developed and based on the MP to DOC concentration ratio in the adsorber influent, BVs to 10% MP breakthrough in the PD-RSSCT (BV10%,PD-RSSCT), and pH-dependent octanol-water partition coefficient (log D). In the second approach, BV10%,full-scale was directly predicted from BV10%,PD-RSSCT. These relationships were verified by adequately predicting full-scale GAC breakthrough curves for several MPs in a fifth water from a drinking water treatment plant on the Ohio River. [ABSTRACT FROM AUTHOR]

The overall goal of this research was to understand and quantify the impact of dissolved organic matter (DOM) quantity and character on the granular (GAC) adsorption of the carcinogenic volatile organic compound (cVOC) 1,2 dichloroethane (1,2 DCA). Three different groundwaters and one surface water were spiked with low concentrations of cVOCs (0.1–50 μg=L) and treated with GAC using bench-scale flow-through adsorbers with empty bed contact times (EBCTs) of 7.5 and 15 min. Little difference—less than 10%—was found in breakthrough behavior as a function of EBCT. Relative to results in clean water, DOM reduced GAC capacity for 1,2 DCA by almost 50%. Unlike other efforts with low- and sub-μg=L influent target compound concentrations, this effort did not find normalized target compound breakthrough to be independent of influent concentration. The lack of an EBCT effect and dependence on influent 1,2 DCA concentration were attributed to the DOM’s weak adsorbing character and its low concentrations. Regressions to predict column breakthrough were created that combined a fluorescent indicator, a total organic carbon (TOC) mass term, and a target compound mass term from 19 column runs with R2 values greater than 0.83. [ABSTRACT FROM AUTHOR]

Prior research has established that pyrolysis temperature during charcoal production is the primary variable influencing adsorption capacity. The first objective of this work was to monitor thermal conditions during charcoal production within three common traditional kiln models. Then, a programmable laboratory furnace pyrolyzer was used to generate chars from eucalyptus, pine, and longan woods and bamboo under a similar range of thermal conditions as identified in the field study. Using chars produced from the furnace, the second objective of this study was to investigate the influence of biomass feedstock and grain size, peak pyrolysis temperature, and duration of thermal treatment on 2,4-D herbicide sorption capacity. A third objective was to determine if chars produced in the laboratory furnace using thermal profiles similar to those observed in the horizontal drum kiln would exhibit similar adsorbent characteristics to kiln charcoals. Field observations revealed significant variability in temperature profiles during pyrolysis in traditional charcoal kilns, and laboratory experiments indicated corresponding variability in equilibrium 2,4-D uptake from surface water ranging from virtually no adsorption to around 10% of the adsorption capacity of commercial activated carbon. Increasing pyrolysis temperature or duration increased 2,4-D adsorption capacity, whereas feedstock did not affect adsorption capacity for the materials studied. Similar herbicide adsorption capacity was observed for furnace chars and kiln charcoals generated using similar thermal profiles. The difficulty of achieving precise temperature control with traditional charcoal production systems contributes to wide thermal variability within and between batches, which translates to wide variability in adsorption of organic compounds. [ABSTRACT FROM AUTHOR]

Though new water supply source development has always required planning under many forms of uncertainty, climate change presents an added dimension that may exacerbate supply and water quality challenges. Hence, new decision-support tools are needed, and in this paper an approach that incorporates the uncertainty of climate variability and change into a cost assessment framework for a municipal drinking water provider in Colorado is developed and applied. The water utility provider is developing a new source of water supply, but treatment costs are relatively high because of the advanced processes needed to treat the water to desired standards. Furthermore, the new water source has variable salinity concentrations that are not removed by any of the implemented treatment processes, requiring blending with an existing lower salinity water source. This results in an increase in the finished water salinity (as compared with the existing water source), which can have negative impacts on customer satisfaction and the life span of water-using appliances. To plan for the development of this water supply source, an approach is proposed to assess the potential treatment and residential costs associated with the blending of the new water source with an existing source under climate uncertainty. Uncertainty from climate variability is captured through a previously developed stochastic streamflow and water quality simulation method that utilizes climate change scenarios. Results show that the proposed blend strategies incur increased treatment costs and economic impacts for customers. Specifically, a 30% reduction in annual flows from climate change translates into a 12% treatment cost increase and a 22% rise in residential costs. [ABSTRACT FROM AUTHOR]

Although information about climate change and its implications is becoming increasingly available to water utility managers, additional tools are needed to translate this information into secondary products useful for local assessments. The anticipated intensification of the hydrologic cycle makes quantifying changes to hydrologic extremes, as well as associated water quality effects, of particular concern. To this end, this paper focuses on using extreme value statistics to describe maximum monthly flow distributions at a given site, where the nonstationarity is derived from concurrent climate information. From these statistics, flow quantiles are reconstructed over the historic record and then projected to 2100. This paper extends this analysis to an associated source water quality impact, whereby the corresponding risk of exceeding a water quality threshold is examined. The approach is applied to a drinking water source in the Pacific Northwest United States that has experienced elevated turbidity values correlated with high streamflow. Results demonstrate that based on climate change information from the most recent Intergovernmental Panel on Climate Change assessment report, the variability and magnitude of extreme streamflows substantially increase over the 21st century. Consequently, the likelihood of a turbidity exceedance increases, as do the associated relative costs. The framework is general and could be applied to estimate extreme streamflow under climate change at other locations, with straightforward extensions to other water quality variables that depend on extreme hydroclimate. [ABSTRACT FROM AUTHOR]

Though climate forecasts offer substantial promise for improving water resource oversight, additional tools are needed to translate these forecasts into water-quality-based products that can be useful to water utility managers. To this end, a generalized approach is developed that uses seasonal forecasts to predict the likelihood of exceeding a prescribed water quality limit. Because many water quality standards are based on thresholds, this study utilizes a logistic regression technique, which employs nonparametric or 'local' estimation that can capture nonlinear features in the data. The approach is applied to a drinking water source in the Pacific Northwest United States that has experienced elevated turbidity values that are correlated with streamflow. The main steps of the approach are to (1) obtain a seasonal probabilistic precipitation forecast, (2) generate streamflow scenarios conditional on the precipitation forecast, (3) use a local logistic regression to compute the turbidity threshold exceedance probabilities, and (4) quantify the likelihood of turbidity exceedance corresponding to the seasonal climate forecast. Results demonstrate that forecasts offer a slight improvement over climatology, but that representative forecasts are conservative and result in only a small shift in total exceedance likelihood. Synthetic forecasts are included to show the sensitivity of the total exceedance likelihood. The technique is general and could be applied to other water quality variables that depend on climate or hydroclimate. [ABSTRACT FROM AUTHOR]

Linear regression techniques were used to develop practical models to predict total organic carbon (TOC) breakthrough in bituminous granular activated carbon (GAC) adsorbers. Models were developed for two field-scale GAC sizes (8×30 and 12×40 mesh) and two empty bed contact times (EBCTs) (10 and 20 min). Model input parameters include two water quality variables, influent TOC concentration (TOC0) and pH, that impact performance. The dependent variables for the models were normalized breakthrough time, throughput in bed volumes, to six fractional (TOC/TOC0=0.2, 0.3, 0.4, 0.5, 0.6, and 0.7) and three mass (TOC=1.0, 1.5, and 2.0 mg/L) effluent concentrations. Model development was performed using small-scale breakthrough data from 35 different source waters; external model validation was performed with small-scale breakthrough data from 14 source waters; a sensitivity analysis was performed to ensure that the models effectively capture expected breakthrough trend; and a scalability test was performed to verify the models’ ability to predict breakthrough for field-scale GAC adsorbers. [ABSTRACT FROM AUTHOR]

Predicting the behavior of natural organic matter (NOM), alkalinity, and pH during drinking water coagulation is difficult because of the heterogeneous chemical nature of NOM and the complexity of carbonate chemistry. Parametric and nonparametric statistical regression methods were implemented to model the removal of NOM, as measured by total organic carbon (TOC), from raw water by conventional surface water treatment and to track the behavior of pH and alkalinity. The United States Environmental Protection Agency (U.S. EPA) Information Collection Rule (ICR) database was sampled for raw water and postsedimentation data from conventional surface water plants. All models were evaluated in terms of their fit and predictive capability, and for all variables explored, the nonparametric local polynomial models outperformed their parametric linear least-squares counterparts. This was most pronounced with the pH model, and was attributed to the nonlinear relationship found between pH and one of the predictors. Between the sedimentation basin and the plant effluent, alkalinity was found to remain relatively constant, TOC decreased by 12% by filtration, and pH increased, consistent with chemical additions required to minimize corrosion in the distribution system. Modeling efforts in this article are meant to be complementary to previous chemical and process models of water treatment. [ABSTRACT FROM AUTHOR]

A nonparametric, nonlinear regression technique—which is introduced to the environmental engineering community in this article—was used to develop models to predict total organic carbon (TOC) breakthrough time for a wide assortment of granular activated carbon (GAC) adsorbers. The models were developed using breakthrough data extracted from the U.S. EPA's Information Collection Rule (ICR) treatment studies database and included breakthrough results from 221 small-scale tests performed using 35 different source waters. Model development included an evaluation of twelve independent (and possibly correlated) variables, of which only four proved to be of statistical importance: influent TOC concentration, pH, empty bed contact time (EBCT), and field-scale GAC size. The predictive capability and overall robustness of the models were evaluated using three methods. First, the models were externally validated using smalland field-scale breakthrough data. Second, a sensitivity analysis was performed to ensure that the models effectively capture expected breakthrough trends. Finally, the models were directly compared to other empirical models reported in the literature, which were developed using traditional linear regression techniques. [ABSTRACT FROM AUTHOR]

Almost half of the world's population is living without access to sanitation services that are safe, reliable, and minimize public health risk of human waste exposure. Modern flush-based sanitation networks are unsustainable: substantial resources, namely water and fuel, are required to bring human waste to centralized treatment facilities. Moving toward sustainable sanitation requires the implementation of innovative renewable energy technologies for stabilization and disinfection of waste, at the local or household scale, where minimal inputs of water, electricity or chemicals are required. A novel solar thermal disinfection toilet prototype has been constructed and is assessed for overall solar to receiver efficiency in treating waste without electrical, chemical, or water inputs from municipal supply. The measured solar to receiver efficiency is 28%, incorporating the capturing and concentration of sunlight and transmission of the energy to the receiver. For a typical sunny day, the current system can achieve thermal treatment of 0.8 kg human waste in roughly 100 min. The novel toilet is available for any location in the world with sufficient sunlight and irradiance data, and is scalable by adding solar collectors for sizes from single dwellings to communities. [ABSTRACT FROM AUTHOR]