bluuebunny/crossref_metadata_2025 huggingface dataset:
Disinfection in the Americas: A Necessity
Authors: Otterstetter Horst , Craun Gunther
Published: February 2018

For more than 80 years, the disinfection of drinking water, primarily with chlorine, has been the cornerstone of public health programs to prevent waterborne infectious diseases. Until 1974, the only concerns about chlorination were how to apply it universally and how to improve its efficiency. Concerns began to change after the discovery that naturally occurring organic materials in some water sources react with chlorine to form chloroform and other trihalomethanes. As other disinfection byproducts (DBPs) were identified in treated drinking water, worries about potential health risks, especially cancer, that might be associated with disinfection have sometimes overshadowed the real threat of infectious waterborne diseases.
Microfiltration operating costs
Authors: Gere Andrew R.
Published: February 2018

Microfiltration provides affordability, reliability, and superior finished water at the San Jose Water Company.

In February 1994, the San Jose (Calif.) Water Company began operating a 5‐mgd (19 × 103–m3/d) microfiltration (MF) plant as part of the Saratoga Water Treatment Plant. The cost of operating the MF plant during 1995 was determined for all noncapitalized expenditures including power, operator labor, chemicals, membrane replacement, maintenance, and repairs. Actual operating costs were $309/mil gal ($82 × 103/m3). Production costs for a direct filtration plant treating similar water during the same time period were 20 percent of those for the Saratoga MF plant, largely because of a significant economy of scale and lower power costs. Treatment plant performance, reliability, and operating experience affect the overall cost of treated water. In its fourth year of operation, the MF plant continues to be appropriate for this water supply because it is reliable and easy to operate and provides superior finished water quality.
Nanofiltration: from prototype to full scale
Authors: Ventresque Claire , Turner Greg , Bablon Guy
Published: February 2018

A nanofiltration membrane tailor‐made to address site‐specific concerns proves capable of overcoming both variable operating conditions and inherent membrane deficiencies.

At a water facility in the Paris suburbs, a prototype nanofiltration (NF) plant was used to assess NF membrane performance prior to design and construction of a large‐scale expansion to an existing plant. Prototype operation uncovered both the successes and deficiencies in membrane performance, particularly with regard to the source water supplying the plant. In response to these concerns, a new membrane was developed in partnership with the membrane manufacturer. In parallel with the prototype work conducted in France, a similar membrane assessment was carried out in England. Results from both pilot‐plant operations indicate that an NF membrane manufactured to meet site‐specific concerns can overcome variable operating conditions and treat large water flows.
Arsenic removal by RO and NF membranes
Authors: Waypa John J. , Elimelech Menachem , Hering Janet G.
Published: February 2018

RO and tight NF membranes prove equally effective in removing As species over a wide range of operational conditions.

Bench‐scale experiments were performed to assess the effectiveness of reverse osmosis (RO) and nanofiltration (NF) membranes in removing arsenic (As) from synthetic freshwater and source water. The authors examined the effects of operational conditions (applied pressure and feedwater temperature) and solution chemical composition (As oxidation state, pH, and presence of co‐occurring inorganic solutes). Both As(V) and As (III) were effectively removed from synthetic freshwater by RO and tight NF membranes over a wide range of operational conditions. The relatively large molecular weight (>125 g/mol) of the As species governed their separation behavior. Applied pressure had little effect on As removal, but an increase in feedwater temperature decreased As removal by a small percentage. Removals of As (III) and As(V) were comparable, with no significant preferential rejection of As(V) over As (III). Variations in solution pH from 4 to 8 also did not affect the removal of As species by the membranes tested, despite changes in the speciation and charge of As(V). Co‐occurring inorganic solutes had only a slight effect on As removal. Removal of As from source water was comparable to that obtained with synthetic freshwater, despite the presence of turbidity, natural organic matter, and a variety of co‐occurring solutes.
Biological filtration for BOM and particle removal: a critical review
Authors: Urfer Daniel , Huck Peter M. , Booth Stephen D.J. , Coffey Bradley M.
Published: February 2018

The authors review key parameters and engineering variables influencing biological filtration and identify areas requiring further research.

Biological filtration, an important process step for the production of microbially safe and aesthetically pleasing drinking water, has attracted increased attention within the water industry. In many cases, the most economical way to implement biological rapid filtration is to achieve biodegradable organic matter (BOM) removal and particle removal within the same filter unit, i.e., single‐stage biological filtration. This requires optimization of the filtration process, keeping in mind both treatment goals: BOM and particle removal. This article presents a critical review of the key parameters and engineering variables influencing the biological performance, as well as the conventional performance, of biologically active filters. Several areas requiring further research have been identified.
Crypto and Giardia in US groundwater
Authors: Hancock Carrie M. , Rose Joan B. , Callahan Michael
Published: February 2018

Groundwater systems need to be carefully monitored until contamination levels and acceptable risk factors are determined.

Data generated from the detection of Cryptosporidium oocysts and Giardia cysts in 463 groundwater samples were compiled. Samples were taken from 199 sites in 23 of the 48 contiguous states. The groundwater sources were vertical wells, springs, infiltration galleries, and horizontal wells. Samples were analyzed using an immunofluorescence technique. Inclusion of data from all sources showed that 12 percent of the sites were positive for Cryptosporidium or Giardia or both. Cryptosporidium oocysts were found in 5 percent of the vertical wells, 20 percent of the springs, 50 percent of the infiltration galleries, and 45 percent of the horizontal wells. Giardia cysts were found in 1 percent of the vertical wells, 14 percent of the springs, 25 percent of the infiltration galleries, and 36 percent of the horizontal wells. These data suggest that springs are at a higher risk for contamination than vertical wells. Because pathogens occur frequently in infiltration galleries and horizontal wells, these sources warrant further study.
Removing particles and THM precursors by enhanced coagulation
Authors: Vrijenhoek Eric M. , Childress Amy E. , Elimelech Menachem , Tanaka Theodore S. , Beuhler Mark D.
Published: February 2018

A pilot‐scale study shows that enhanced coagulation removes both particles and THM precursors.

The effectiveness of enhanced coagulation for removing particles and trihalomethane (THM) precursors at various alum dosages and coagulation pH values was assessed. Samples of both source water and filter effluent were examined by counting particles and measuring particle size distribution, turbidity, total organic carbon, ultraviolet light absorbance at 254 nm (UV254), and THM formation potential. Removal of particles and turbidity increased substantially at alum dosages above 20 mg/L. Particle removal was not significantly different at adjusted pH (5.5) compared with ambient pH. Filter effluent particle counts were consistent with residual turbidity data; however, particle counting provided more information on the efficiency of the solid‐liquid separation. Significantly more THM precursors were removed by enhanced coagulation at pH 5.5 than at ambient pH. Higher dosages were needed to achieve acceptable removal of THM precursors than were needed for removal of particles.
Technical note: adsorption capacity of GAC for synthetic organics
Authors: Speth Thomas F. , Miltner Richard J.
Published: February 2018

Isotherms of 15 compounds in organic‐free water are presented.

Isotherms are presented for 15 compounds in organic‐free water. The compounds—ranging from pesticides to disinfection by‐products—are all of regulatory interest.
Monitoring DBP formation with differential UV spectroscopy
Authors: Li Chi‐Wang , Korshin Gregory V. , Benjamin Mark M.
Published: February 2018

A new application uses differential UV spectroscopy to monitor DBP formation easily, rapidly, and inexpensively.

The decrease in the ultraviolet (UV) absorbance of natural organic matter (NOM) induced by chlorination can be characterized by the differential UV spectrum of the water. Differential UV spectra of chlorinated NOM are remarkably similar for a wide range of water qualities and chlorination conditions, always exhibiting a band with a maximum near a wavelength of 272 nm. The magnitude of the decrease in A272 (ΔA272) is an excellent indicator of total organic halogen (TOX) formation resulting from chlorination, independent of the ratio of chlorine to dissolved organic carbon, bromide concentration, pH, reaction time, and NOM source. Use of ΔA272 as a surrogate allows virtually instantaneous and continuous monitoring of TOX and in some cases, specific disinfection by‐products, at a much lower cost than is possible using conventional analytical approaches.
Effects of backwashing on biological filters
Authors: Ahmad Rasheed , Amirtharajah A. , Al‐Shawwa A. , Huck Peter M.
Published: February 2018

A pilot study identifies concerns and strategies for successful performance of biological filters.

The success of biological filtration depends on careful control and maintenance of the amount of biomass on the media during the maturation period and backwashing as well as during sudden changes in hydraulic loading. Various backwashing strategies and hydraulic transients were studied to determine how they affected filtration performance of biofilters in terms of effluent quality and head loss. Biological filters backwashed with a combination of air plus subfluidization water flow at collapse pulsing, followed by water wash with 25 percent bed expansion, can produce a water low in assimilable organic carbon (AOC). Compared with air‐scoured filters, water‐washed filters produced lower initial peaks during ripening and similar effluent AOC. Chlorinated backwash affects biological activity. Under the conditions of these experiments, chlorinated backwash produced higher AOC and nonpurgeable organic carbon in the filter effluent. A sudden 30 percent increase in hydraulic loading had a greater effect on biological filtration performance than on conventional filtration, accelerating filter breakthrough and causing poorer effluent quality.
Maintaining quality without a disinfectant residual
Authors: van der Kooij Dick , Hein J. , van Lieverloo M. , Schellart Jon , Hiemstra Peter
Published: February 2018

Good engineering practices and biostable drinking water and materials help ensure the quality of Dutch drinking water during distribution without use of a disinfectant residual.

Preservation of the microbial quality of drinking water during distribution is a main objective in water supply. Although a disinfectant residual reduces the concentration of suspended bacteria, it has only a limited effect on microorganisms in biofilms and sediments or on microbial contaminants. Furthermore, a disinfectant residual affects taste and odor and results in the presence of compounds with toxic properties. Maintenance of an effective residual throughout the distribution system is hampered by disinfectant decay caused by pipe materials and compounds present in the water. The Netherlands depends on good engineering practices in the distribution system to prevent microbial and chemical contamination. Regrowth can be limited by distributing biostable drinking water and applying biostable materials in contact with drinking water.
Benefits of using a disinfectant residual
Authors: Haas Charles N.
Published: February 2018

Given the age and vulnerability of some US water distribution systems, use of a disinfectant residual as an added safeguard makes sense.

Water distribution systems in the United States routinely carry chlorine residuals < 0.05 mg/L and invariably carry residuals > 0.1 mg/L. This article outlines some of the benefits of using chlorine as a disinfectant residual and considers system characteristics (e.g., system age and vulnerability) that support this application. Benefits accruing to maintenance of a chlorine residual include protecting against modest degrees of intrusion of contaminants, serving as a sentinel for the presence of such contamination, and reducing the potential for growth of heterotrophic organisms.
Complying With the Interim Enhanced Surface Water Treatment Rule
Authors: Pontius Frederick W.
Published: February 2018

On Dec. 16, 1998, the US Environmental Protection Agency (USEPA) published the Interim Enhanced Surface Water Treatment Rule (IESWTR)1 as required by the Safe Drinking Water Act. The purpose of the IESWTR is to improve the control of microbial pathogens, including Cryptosporidium, in drinking water and to ensure microbiological quality as water systems comply with the Stage 1 Disinfectants/Disinfection By‐products (D/DBP) Rule.2 USEPA estimates that endemic illness from Cryptosporidium will decrease by 110,000 to 463,000 cases annually. The IESWTR will reduce the likelihood of an outbreak of cryptosporidiosis by providing a larger margin of safety.
Comparison of mineral acid pretreatments for sulfide removal
Authors: Duranceau Steven J. , Anderson Robert K. , Teegarden Robert D.
Published: February 2018

Both sulfuric and carbonic acid improved sulfide removal by lowering pH, but only carbonic acid preserved alkalinity and proved less corrosive.

To determine water quality effects on groundwater treatment for hydrogen sulfide, the authors compared sulfuric acid (H2SO4) and carbonic acid for pH adjustment pretreatment in a pilot‐scale (40‐gpm [2.5‐L/s]) randomly oriented packed tower. Pretreatment with either H2SO4 or carbon dioxide (CO2) to pH 6.0 resulted in > 95 percent sulfide removal for tower feedwater sulfide concentrations of 2.5 mg/L. However, utilization of H2SO4 for pH adjustment resulted in a loss of alkalinity in the finished water and an increase in sulfur (as sulfate), whereas CO2 pretreatment preserved alkalinity in the finished water and did not increase sulfur (as sulfate).
Economic analysis for replacing residential meters
Authors: Yee Michael D.
Published: February 2018

Statistical sampling was used to chart the degradation of water meter accuracy over time and to determine an optimal replacement age.

Single‐family residential 0.6‐in. (15‐mm) meters make up about 90 percent of all meters for the Alameda County Water District in Fremont, Calif., and generate about half of all annual revenues from water consumption. Like all mechanical devices, these meters degrade in accuracy over time, resulting in an increasing amount of lost revenue. To increase meter accuracy requires replacing meters at an additional cost. The optimal economic replacement age is when the average cost per year (cumulative lost revenue plus replacement cost divided by meter age) is at a minimum. Statistical sampling was used to profile the degradation of these meters' accuracy over time. The annual lost revenue over time was then calculated. When economic and operational factors were considered, the optimal age at which to replace residential meters in the district was determined to be 15 years.
Committee Report: Emerging pathogens–bacteria
Authors:   AWWA Research Division Microbiological Contaminants Research Committee
Published: February 2018

Organisms that may not be well known to water suppliers are highlighted.

The AWWA Research Division Microbiological Contaminants Committee reviewed four bacterial microorganisms considered of greatest concern to the water industry: Mycobacterium avium complex, Helicobacter pylori, pathogenic Escherichia coli, and Campylobacter jejuni. To help the water quality specialist, this report describes each organism; reviews its health effects; summarizes information on its occurrence, waterborne outbreaks, and treatment; discusses analytical procedures; and outlines needed research.
Integrating high‐rate DAF technology into plant design
Authors: Edzwald James K. , Tobiason John E. , Amato Tony , Maggi Lawrence J.
Published: February 2018

Pilot‐plant studies of DAF technology indicate flocculation times can be shortened and hydraulic loading rates significantly increased without loss of performance.

Compared with sedimentation, dissolved‐air flotation (DAF) is a more efficient clarification process for separating floc particles, which are often low in density. This article investigates the use of short flocculation times with high DAF and filter hydraulic loading rates and examines the feasibility of integrating high‐rate DAF technology into water facility design. Research was conducted at pilot scale using two water sources of varying quality. Numerous runs were carried out under extremely conservative cold water conditions of 3‐5oC. The most important research finding is that integration of high‐rate DAF treatment technology is feasible. DAF treatment facilities may be designed and operated with flocculation times of 5 min, DAF hydraulic loading rates of 30‐40 m/h (12‐16 gpm/sq ft) depending on water temperature, and high filtration rates of 20 m/h (8 gpm/sq ft). At higher DAF loading rates, excess air bubbles can be eliminated by internal or external air removal methods.
Environmental Justice and Drinking Water Regulations
Authors: Pontius Frederick W.
Published: February 2018

The Environmental Justice (EJ) movement is relatively new, appearing on the drinking water regulatory policy scene in the early 1990s. It combines concern for environmental protection and for impoverished minority communities. Until recently, water suppliers were only peripherally involved with the EJ movement, which has focused most of its efforts on pollution from industrial sites. The US Environmental Protection Agency's (USEPA's) recently issued proposed rule for radon is the first drinking water rule to directly address EJ issues. This article reviews the relevance of EJ to drinking water regulation.
Using surrogates to improve plant performance
Authors: Nieminski Eva C. , Bellamy William D. , Moss Linda R.
Published: February 2018

To achieve maximum treatment effectiveness, operators need a tool to determine how well their plants are optimized for pathogen removal.

This article presents the results of a study designed to evaluate the use of pathogen surrogates as a tool in treatment optimization and to predict pathogen occurrence. A comprehensive matrix was developed to relate water quality and process variables for 24 potable water sources and 12 possible surrogates to the target pathogens of Giardia, Cryptosporidium, and enteric viruses. No “ideal” surrogate for predicting occurrence of protozoan pathogens or treatment performance was identified because of analytical constraints and low pathogen occurrence. However, it was concluded that aerobic spores and particle counts could be used as surrogate measures to evaluate or improve treatment plant performance. Utilities should select not one but a number of surrogates to assess raw water quality and treatment plant performance.
Modeling DBP formation
Authors: Sung Windsor , Reilley‐Matthews Betsy , O'Day D. Kelly , Horrigan Kristin
Published: February 2018

Disinfection by‐product concentrations in a transmission system can change in response to downstream treatment processes.

Semimechanistic models that describe the formation of disinfection by‐products (DBPs) (including trihalomethanes and haloacetic acids) were developed for the Massachusetts Water Resources Authority, an unfiltered surface water system using chlorine. The model's parameters were hydroxide concentration, chlorine decay kinetics or chlorine reacted, ultraviolet light absorbance at 254 nm, and algae concentration. One of the challenges in estimating or predicting DBP concentrations is that treatment processes at various points in the transmission system have substantial effects on the factors that affect DBP formation and rates of DBP formation. This article describes the formation of total trihalomethanes and haloacetic acids in the Massachusetts Water Resources Authority system and takes into account three treatment processes within the system. Coefficients used in the model were based on monitoring data collected from October 1997 to July 1999 and were validated with monitoring data from August 1999 to January 2000.
Climate and waterborne disease outbreaks
Authors: Rose Joan B. , Daeschner Scott , Easterling David R. , Curriero Frank C. , Lele Subhash , Patz Jonathan A.
Published: February 2018

This preliminary descriptive study describes the temporal and spatial distribution of US waterborne disease outbreaks using a geographic information system approach in relationship to rainfall.

Regional climate change and variability and their effect on water resources have not been the subject of much study. Climate predictions suggest that storms will be of greater intensity and that the average precipitation event is likely to be heavier. Rainfall and runoff have been associated with individual outbreaks of waterborne disease caused by fecal‐oral pathogens. Waterborne disease outbreak data from 1971 through 1994 were analyzed for groundwater and surface water in 2,105 US watersheds. Between 20 and 40 percent of outbreaks were associated with extreme precipitation. This relationship with extreme precipitation was found to be statistically significant for both surface water and groundwater, although it was more apparent with surface water outbreaks. The authors offer recommendations for improving the assessment of changes in water quality and the effect that climate variability and environmental factors have on waterborne disease risk.
Risk Perception and Bottled Water Use
Authors: Anadu Edith C. , Harding Anna K.
Published: February 2018

This paper discusses a study of four communities in Oregon that were divided into two control groups and surveyed according to water contamination problems and how their perceptions of risk affected their use of tap water versus bottled water. Results indicated that risk perception about drinking water appears to be affected by three factors: the consumer's level of awareness of a problem; the presence or absence of drinking water contamination problems; and, the chronicity of the problem. Findings suggest that water contamination problems contribute to increased levels of risk perception with those drinking tap water. Also, long‐term problems that are not easily solved by the water utility may heighten consumers' perception of risk. Higher levels of risk perception may be the driving force behind higher rates of bottled water use in some communities.
Giardia and Cryptosporidium Removals by clarification and filtration under challenge conditions
Authors: Edzwald James K. , Tobiason John E. , Parento Leah M. , Kelley Michael B. , Kaminski Gary S. , Dunn Howard J. , Galant Peter B.
Published: February 2018

This research examined removals of Giardia and Cryptosporidium by clarification (either dissolved‐air flotation [DAF] or plate sedimentation) and by dual‐media filtration following clarification. Studies were conducted for challenge conditions of cysts and oocysts (i.e., high influent concentrations) and for process design detention times and hydraulic loadings. To evaluate the effect of water temperature on performance, sets of experiments were performed for winter and spring seasons. DAF clarification performed better than plate sedimentation and consistently resulted in lower turbidity levels and particle counts. Overall log removals of Giardia and Cryptosporidium by clarification and filtration were about the same for DAF versus plate sedimentation. Although DAF is not recognized under the Surface Water Treatment Rule or the Interim Enhanced Surface Water Treatment Rule, the authors argue that based on these findings, DAF plants should receive Giardia and Cryptosporidium removal credits at least equal to those received by sedimentation plants.
Evaluation of USEPA Method 1622 for detection of Cryptosporidium oocysts in stream waters
Authors: Simmons Otto D. , Sobsey Mark D. , Schaefer Frank W. , Francy Donna S. , Nally Rebecca A. , Heaney Christopher D.
Published: February 2018

To improve surveillance for Cryptosporidium oocysts in water, the US Environmental Protection Agency developed method 1622, which consists of filtration, concentration, immunomagnetic separation, fluorescent antibody and 4, 6‐diamidino‐2‐phenylindole (DAPI) counter‐staining, and microscopic evaluation. Two filters were compared for analysis of 11 stream water samples collected throughout the United States. Replicate 10‐L stream water samples (unspiked and spiked with 100–250 oocysts) were tested to evaluate matrix effects. Oocyst recoveries from the stream water samples averaged 22% (standard deviation [SD] = ±17%) with a membrane disk and 12% (SD = ±6%) with a capsule filter. Oocyst recoveries from reagent water precision and recovery samples averaged 39% (SD = ±13%) with a membrane disk and 47% (SD = ±19%) with a capsule filter. These results demonstrate that Cryptosporidium oocysts can be recovered from stream waters using method 1622, but recoveries are lower than those from reagent‐grade water. This research also evaluated concentrations of indicator bacteria in the stream water samples. Because few samples were oocyst‐positive, relationships between detections of oocysts and concentrations of indicator organisms could not be determined.
Using Coagulation, Flocculation, and Settling to Remove Toxic cyanobacteria
Authors: Drikas Mary , Chow Christopher W.K. , House Jenny , Burch Michael D.
Published: February 2018

Cyanobacteria (blue‐green algae) produce toxins and tastes and odors that can significantly impair water quality. The removal of cyanobacterial cells without cell damage could significantly reduce the concentration of tastes, odors, and toxic cell metabolites present in treated water. Cultured cyanobacterium, hepatotoxic Microcystis aeruginosa, was mixed with reservoir water to simulate water entering a treatment plant during an algal bloom. A bench‐top jar‐test apparatus (flocculation) and a full‐scale pilot plant (flocculation–sedimentation–filtration) rated at 600 mL/min were used to evaluate the effectiveness of conventional water treatment processes in removing cyanobacterial cells. Removal of cells by flocculation using a jar‐test apparatus with aluminum sulfate dosed at concentrations used in water treatment practice varied between 70 and 83%. Results obtained from the pilot experiment indicated 99.9% of the cells were removed. More important, no additional release of microcystin (toxin) was found in the finished water.
The Cost‐Effectiveness of Water Conservation
Authors: Platt Jennifer L. , Delforge Marie Cefalo
Published: February 2018

The Town of Cary, North Carolina, has found that a carefully planned water conservation program can offer real solutions to real problems. By making the most of existing water supplies, Cary's conservation efforts have helped create a “new” source of water and enabled the town to delay two future plant expansions by a total of 10 years, at a cost of $138/mil gal ($37/ML) of water saved. This paper offers an overview of Cary's long‐term water conservation program and its associated costs and benefits.
THE WHO, WHAT, WHY, AND HOW OF Counter terrorism Issues
Authors: Denileon Gay Porter
Published: February 2018

This article discusses how concern regarding an intentional terrorist attack on US infrastructure that would include water systems has heightened considerably since the end of the Cold War. Because guns and explosives are easier to obtain than large amounts of contaminants or toxic chemicals, the most likely scenario for a terrorist attack on a water system would involve physical destruction of the system's components to disrupt the supply of water, rather than actions that would cause a contamination event. Five types of perpetrators are discussed in this article, along with a listing of available resources to help utilities improve security at their facilities.
Case Study: Ozonation and distribution system biostability
Authors: Escobar Isabel C. , Randall Andrew A.
Published: February 2018

Biodegradable organic matter that is not removed during water treatment can lead to the proliferation of bacteria within the distribution system. This, in turn, can deteriorate water quality, accelerate corrosion rates of pipes, and potentially increase the incidence of bacteriological diseases. The main objective of this project was to collect and analyze full‐scale system data on short‐term and long‐term responses to the implementation of ozonation with respect to its impact on bacterial regrowth potential as quantified by assimilable organic carbon (AOC) and biodegradable dissolved organic carbon (BDOC). A major observation made during the sampling period was that ozonation caused a significant increase in the AOC concentration of the distribution system (more than 200% in the short term and more than 100% in the long term). Use of ozone also caused a significant increase in the bacterial counts within the distribution system for both the long and short terms. In contrast, ozonation affected BDOC and dissolved organic carbon (DOC) concentrations only slightly compared with its impact on AOC concentrations. However, this may be because of the source water, which had low DOC and BDOC concentrations (1.2 and 0.11 mg/L, respectively).
Characterization of Oxidation processes: ozonation and the AOP O3/H2O2
Authors: Acero Juan L. , Von Gunten Urs
Published: February 2018

The influence of water quality parameters (dissolved organic matter and alkalinity) on the efficiency of the ozone/hydrogen peroxide (O3/H2O2) advanced oxidation process (AOP) relative to the corresponding conventional ozonation process was investigated. In natural waters with a high natural organic matter content (≥3 mg/L), O3 decomposition is controlled by radical‐type chain reactions. Thus, the overall OH radical oxidation capacity is nearly independent if conventional ozonation is replaced by O3/H2O2 AOP. In contrast, when the organic matter content in the natural water is low (≤1 mg/L), the addition of H2O2 considerably enhances the oxidation capacity by OH radicals. A constant ratio between the OH radical and O3 concentration (Rct) was found during both treatments, making it possible to predict the oxidation of micropollutants with O3 and OH radicals if the rate constants of both oxidants are known. The oxidation of atrazine during ozonation and the combined process O3/H2O2 could be accurately predicted in natural waters.
Field Evaluation of As Removal by IX and AA
Authors: Wang Lili , Chen Abraham S.C. , Sorg Thomas J. , Fields Keith A.
Published: February 2018

A study was conducted at two ion‐exchange (IX) and two activated alumina (AA) water treatment plants in New England to evaluate the performance of these full‐scale systems for consistently removing arsenic (As) from raw water. The source water in this study contained 34–87 μg/L of total As, consisting primarily of As(V), except for one system in which 0.3–28.8 μg/L of As(III) was measured. Results of the yearlong field sampling indicated the IX and AA systems were capable of removing As to < 5 μg/L in the treated water, provided IX resins were properly regenerated and AA media were changed out at a proper frequency. Special efforts were made to examine unusual performance results observed during the study.
Effect of operating conditions on Bromate Removal Efficiency in BAC filters
Authors: Kirisits Mary Jo , Snoeyink Vernon L. , Chee‐Sanford Joanne C. , Daugherty Becky J. , Brown Jess C. , Raskin Lutgarde
Published: February 2018

This study examined the use of biologically active carbon (BAC) filters for microbial reduction of bromate to bromide. In these filters, abiotic reduction by the activated carbon did not play a significant role in bromate removal. Bromate removal in a BAC filter decreased by 30% after a system perturbation, suggesting that filter history affects bromate removal. Although 25 and 51 mm (1 and 2 in.) inner‐diameter BAC filters provided comparable bromate removals for the tested contact times, the larger filter exhibited nitrite production; therefore, system performance must be monitored to prevent such undesirable compounds from entering the water. The mass of bromate removed increased as the influent bromate concentration increased, whereas bromate removal did not change after backwashing. Experimental evidence indicated that increased regrowth would not be observed in the distribution system following BAC filtration with a low influent dissolved oxygen concentration (2 mg/L) in the tested water.
Short‐term water demand forecast modeling techniques—CONVENTIONAL METHODS VERSUS AI
Authors: Jain Ashu , Ormsbee Lindell E.
Published: February 2018

A variety of forecast modeling techniques, from conventional techniques such as regression and time series analyses to relatively new artificial intelligence (AI) techniques such as expert systems and artificial neural networks (ANNs), were investigated for use in short‐term water demand forecasting. Daily water demand, daily maximum air temperature, and daily total rainfall data from Lexington, Ky., for 1982–92 were used to develop and test several forecast models. The performance of each model was evaluated using two standard statistical parameters. On the basis of the measured statistical parameters, the AI models outperformed the conventional models. Both expert system and ANN technologies should be further explored by water utility engineers and managers because these techniques have the potential to enhance the operational performance of various water supply and delivery systems.
Ontario on fast track to drinking water quality management
Authors: Scharfenaker Mark A.
Published: February 2018

This article discusses recommendations made by a months‐long formal inquiry into the Walkerton cryptosporidiosis outbreak. Commissioner Dennis R. O'Connor stressed the critical importance of quality management at the water utility level for ensuring the prevention of waterborne diseases. O'Connor's plan is especially noteworthy for seeking the first‐ever requirement that all municipal water systems be operated by an agency that is accredited against an industry‐developed and government‐recognized quality management standard. His goal is to have such a standard in place by 2004 and all systems accredited by 2006. This article outlines the accreditation plan developed by AWWA and recommended by O'Connor.
Evaluating Aeration‐Stripping Media on the Pilot Scale
Authors: Narbaitz Roberto M. , Mayorga Wilbur J. , Torres Phillip , Greenfield Jeffrey H. , Amy Gary L. , Minear Roger A.
Published: February 2018

A pilot‐scale air‐stripping study evaluated the performance of numerous full‐size packing materials in the removal of 11 contaminants in up to 10 flow conditions within the range encountered in practice. The overall liquid phase mass transfer coefficients (KLa) were calculated based on the concentrations within the packing (i.e., excluding end effects). For the operating conditions tested, KLa was greatly affected by the liquid loading. The volumetric air‐to‐water (A:W) ratio and the stripping factor (R) had very limited effect on KLa, primarily because the stripping factors were significantly > 1. At the various A:W ratios, the authors found distinct relationships between KLa and pressure drop, which indicated that A:W = 25 was more effective than A:W = 50 and A:W = 100. Because the various packing materials performed quite differently, the optimal designs for the various packings will consist of air‐strippers of somewhat different dimensions operating under different operating conditions. However, the packing materials' low contribution toward the overall cost and the similarity of the various designs reduce the effect of using different materials. Space and height restrictions, tendency to foul, and ease of cleaning may be more critical design factors in the selection of packing.
Perchlorate removal via IRON‐PRELOADED GAC and BOROHYDRIDE REGENERATION
Authors: Na Chongzheng , Cannon Fred S. , Hagerup Ben
Published: February 2018

Tailored granular activated carbon (GAC) can reduce groundwater perchlorate levels from 60–80 μg/L to below detection. Specifically, rapid small‐scale column tests, also called RSSCTs, showed that by preloading GAC with iron–oxalic acid, the GAC adsorption capacity could be improved up to 42%. When the preloaded GAC became saturated with perchlorate, 65–74% of the GAC's original adsorption capacity could be restored by chemically regenerating the GAC with sodium borohydride. This chemical regeneration could be achieved with the use of a small fraction of the water that had been processed during the water treatment cycle. The waste stream from chemical regeneration contained concentrated perchlorate levels as high as 7,000–15,000 μg/L. With this approach, the simulations described in this article indicated that when two tailored GAC beds were operated in series with a 40‐min empty‐bed contact time, they could provide water treatment service for 60–75 days during the first operations cycle; following chemical regeneration, the GAC beds could provide about an additional 30–40 days of water service for several successive treatment and regeneration cycles.
Radium removal by HMO and manganese greensand
Authors: Qureshi Naeem , Nelson Steven
Published: February 2018

In December 2000, the US Environmental Protection Agency published the final radionuclides rule. The standard of 5 pCi/L for combined radium (Ra) 226 and 228 will affect more than 500 US systems and 1.4 million people in 177 cities in the Midwest. The best available technology for Ra removal includes ion exchange, lime softening, and reverse osmosis. However, hydrous manganese oxide and manganese greensand filtration is capable of removing up to 80% of Ra. For plants designed to remove iron and manganese by a manganese greensand filtration system, the cost of removing Ra is minimal. Results of pilot‐ and full‐scale studies are reported from Bellevue Sanitary District 1 in Brown County, Wis.; Knoxville, Iowa; Garretson and Elk Point, S.D.; Marcus, Iowa; and Savage, Lakeville, and Hinckley, Minn. Also discussed are the relationship between total dissolved solids and Ra removal and the disposal of water containing Ra, which is a major concern.
Dechlorination techniques to improve sensory odor testing of geosmin and 2‐MIB
Authors: Worley Jennifer L. , Dietrich Andrea M. , Hoehn Robert C.
Published: February 2018

Chlorine in finished water can mask the more subtle odors of geosmin and 2‐methylisoborneol (2‐MIB), two chemicals that often trigger consumer complaints when present at even nanogram‐per‐litre concentrations. These are two of the odors that are revealed as chlorine dissipates in the distribution system, which is typically at the consumer's end. As a result, odor monitoring at the treatment plant may not identify unpleasant smells because chlorine levels at the plant are typically high and mask the other odors. Proper sensory evaluation of these odor‐causing substances requires that the chlorine odor first be reduced or eliminated so that the secondary odor can be identified. In this study, ascorbic acid, hydrogen peroxide, oxalic acid, sodium thiosulfate, and ultraviolet (UV) irradiation were evaluated for their effectiveness in reducing chlorine solutions and for their subsequent usefulness in sensory analysis. Oxalic acid and UV irradiation were inefficient dechlorinators, and sodium thiosulfate produced a rotten‐egg odor under the study conditions. Triangle testing and flavor profile analysis showed that ascorbic acid and hydrogen peroxide were effective in reducing chlorinous odors without producing new odors, and they did not alter the testers' sensory perceptions of geosmin and 2‐MIB.
Surviving Disasters: Learning from Experience
Authors: Grigg Neil S.
Published: February 2018

Although most utilities have disaster plans, making them work in the face of an actual emergency requires a vigilant, organization‐wide approach to identifying potential threats, whether naturally occurring or human made, and training everyone in the organization how to respond in such an event. A variety of information indicates that threats to water systems and utilities are increasing. This article is of interest to utility managers and regulators because it presents the state‐of‐practice in preparing for and surviving disasters, and it draws primarily on the experience of others in making its recommendations. By considering the organization‐wide approach advocated in the article, water suppliers can improve the security and reliability of their systems.
Partnership Offers New Distribution System Optimization Program
Authors: Lauer Bill
Published: February 2018

This article presents the Partnership for Safe Water (PSW) continuous improvement program, originally developed to help well‐run utilities treating surface water sources to optimize their treatment processes beyond regulatory requirements to provide added protection against Cryptosporidium. The article discusses PSW's fundamental approach, along with the development of the program, the four phases of the Distribution System Optimization Program, the three main components of overall system integrity, and the primary performance indicator for each major system integrity component. A unique feature of the program is that data from performance measures provide evidence of progress toward optimization goals.
Water Affordability: Who's Going to Pick Up the Check?
Authors: Baird Gregory M.
Published: February 2018

This article discusses the issue of whether local utilities will take control and address increasing costs and the resulting affordability concerns that are raised, or shift the responsibility to another party at a higher cost. Although the U.S. water industry faces an unprecedented need for staggering rate increases, a new dialogue of rate straight‐talk is required. The article discusses in detail the following straight‐talk discussion topics: what full‐price costing really means (in order to set realistic expectations with customers and make critical ownership decisions); the need for and the availability of options regarding customer assistance programs; and, the recommended strategies for minimizing cost increases.
The nitrification index: A unified concept for quantifying the risk of distribution system nitrification
Authors: Jr. Gerald E. Speitel , Kannappan Ramakrishnan , Bayer Benjamin M.
Published: February 2018

Nitrification is widespread in drinking water distribution systems that use chloramination as a residual disinfectant. Factors affecting the likelihood of nitrification episodes include pH, monochloramine, trihalomethane (THM), and ammonia concentrations. This research advanced the understanding of the role THMs play in inhibiting distribution system nitrification, placed THMs within the context of the other key factors that determine the risk of nitrification, and developed a fundamental framework for assessing nitrification risks in a way that provides practical guidance to utilities. Laboratory‐scale annular reactor experiments demonstrated the potential of THMs to inhibit nitrification. The nitrification index (NI) was developed from the fundamental kinetics of nitrifier growth and inactivation by monochloramine and THMs. A linear relationship was demonstrated between the rate of nitrification onset and NI values. Tracking the NI over time in distribution systems may provide an effective early warning system that would permit timely adjustments before nitrification begins.
Field pilot evaluations of iron oxide‐based arsenic adsorption media
Authors: Möller Teresia , Bagchi Debanjali , Sylvester Paul
Published: February 2018

Field pilot tests were conducted with three hybrid adsorptive media to evaluate their performance at removing arsenic from groundwater. The media are based on polymeric resins loaded with iron oxyhydroxide nanoparticles and were evaluated with a commercially available granular ferric oxide media as a reference material at well sites in New Hampshire and Arizona. A full‐scale arsenic removal system in Connecticut is also discussed. The water chemistries of these three locations varied in terms of pH, arsenic concentration and speciation, and silica and phosphate content. Although all media were hybrid iron oxide materials, they exhibited different levels of performance and capacity under the specific pilot conditions because the effective operational life to remove arsenic is dependent on the chemistry of the treated water as well as the porosity of the base resin. The availability of the iron phase for arsenic binding is an important parameter, particularly in dynamic column applications.
Evaluation of variability in radionuclide measurements in drinking water
Authors: Eaton Andrew , Cha Yoon , Geddes Linda , Morley Kevin M.
Published: February 2018

A blind interlaboratory study of radium‐226 (Ra‐226), radium‐228 (Ra‐228), and gross alpha and beta activity was conducted among five multistate certified laboratories to examine concerns regarding analytical variability for compliance with the revised Radionuclides Rule. Results of the interlaboratory study demonstrated that although Ra‐226 and gross beta measurements appeared to be both accurate and precise, even at low levels, Ra‐228 and gross alpha measurements were much less robust both within and among laboratories, which could result in potentially incorrect compliance decisions. There are several steps that utilities can take to improve reliability of compliance data, including mandating specific quality control (QC) steps by laboratories and ensuring that they follow the QC guidance in the US Environmental Protection Agency's laboratory certification manual and the Multi‐Agency Radiological Laboratory Analytical Protocols Manual, even though these may not always be enforced by laboratory certification authorities.
Managing Assets: When Going with the Flow Doesn't Save Money
Authors: Baird Gregory M.
Published: February 2018

This article makes an analogy between driving in heavy traffic and asset management, which, like driving, requires education, training, and testing. At some point every utility will need to get behind the wheel and start down a path toward sustainability and affordability. Comprehensive asset management is the long road that must be traveled to reach the desired destination. The good thing is that the road is paved and resources are available, so utilities can ask for help and directions. Benchmarking your current location will enable your utility to explain how far it has traveled and at what cost. Shortcuts and speeding may cause costly mistakes and waste time, but by using consistent, dedicated, and ongoing efforts and improvements, a utility can reach its destination safely. The article makes suggestions on how to map out the route, make adjustments as needed, and follow a plan at a manageable pace.