Molecular Biomarkers and Influential Factors of Denitrification in a Full-Scale Biological Nitrogen Removal Plant.

Three denitrifying bacteria, Paracoccus spp., Thauera spp., Pseudomonas-like spp., and two functional genes, nitrate reductase (narG and napA), were studied as potential biomarkers for total nitrogen removal. These bacterial genera and the functional genes showed significant negative correlations with total nitrogen in the effluent (TNeff). Thauera spp. had the highest correlation (r = -0.793, p < 0.001) with TNeff, and narG-like and napA genes also showed significant correlations (r = -0.663 and -0.643, respectively), suggesting functional genes have equal validity to 16S rRNA genes in monitoring denitrification performance. The most explanatory variables were a combination of constituents, with temperature emerging as the most important in Pearson's correlation and redundancy analysis. Thauera spp. had the highest correlation with temperature (r = 0.739) followed closely by Paracoccus spp. (r = 0.705). Denitrification was also significantly affected by pH (r = 0.369), solids retention time (r = -0.377), total nitrogenin (r = 0.635), and organic matter in the influent (biochemical oxygen demand and chemical oxygen demand; r = 0.320 and 0.522, respectively). Our data verified that major denitrifiers' 16S rRNA genes and nitrate reductase genes were better biomarkers than the biomass concentration, and any of the biomarkers could track denitrification in real time.

Impact of fouling on the decline of aeration efficiency under different operational conditions at WRRFs.

Biofilm formation influences the most energy-demanding process in the waste water treatment cycle. Biofilm growth on the surface of wastewater aeration diffusers in water resource recovery facilities (WRRFs) can increase the energy requirements up to 50% in less than 2 years. The impact of biofilms in aeration diffusers was quantified and assessed for first time using molecular tools (i.e., Energy-dispersive X-ray, Ra and RMS and Pyrosequencing) and state-of-the-art techniques (i.e., EPS quantification, Hydrophobicity and DNA quantification). To provide a better understanding and quantitative connections between biological activity and aeration energy efficiency, two replicates of the most common diffusers were installed and tested in two different operational conditions (higher and lower organic loading rate processes) during 15 months. Different scenarios and conditions provided for first time comprehensive understanding of the major factors contributing to diffuser fouling. The array of analysis suggested that higher loading conditions can promote specialized microbial populations to halve aeration efficiency parameters (i.e., αF) in comparison to lower loading conditions. Biofilms adapted to certain operational conditions can trigger changes in diffuser membrane properties (i.e., biological enhanced roughness and hydrophobicity) and enhance EPS growth rates. Improved understanding of the effects of scaling, biofouling, aging and microbial population shifts on the decrease in aeration efficiency is provided.

Comparison of DNA Extraction Efficiency and Reproducibility of Different Aeration Diffuser Biofilms Using Bead-Beating Protocol.

An existing bead-beating DNA extraction protocol was employed to compare the DNA extraction recovery and fragment quality of 6 different aeration diffuser biofilms. Escherichia coli, Gordonia amarae, and mixed liquor were used as controls. The fraction of total DNAbiofilm decreased monotonically with increasing number of beat beatings (BB) when the amount of DNA present was sufficient (>4 µgDNA/cm2), excluding the ceramic disk. While controls required only 2 BBs, 3 out of 5 BBs achieved ≥70% of total DNA (70.3 ± 1.7%) for 5 out of 6 biofilms. Quantitative polymerase chain reaction (PCR) analyses of 353 and 1,505 basepair (bp) amplicons from pure culture extracts showed target copy numbers were not degraded for the first 2 BBs, but the third BB decreased amplicon concentrations by 0.65 and 1.12 log for E. coli, and 0.39 and 0.40 log for G. amarae, respectively. The 353 bp fragment amplification from biofilm samples showed minimal degradation for the first 3 BBs. PCR and gel electrophoresis confirmed integrity of amplified 1,505 bp DNA fragments over the 5 BBs, except in the EDPM (75 mm diameter, tube) diffuser biofilm (4.98 ± 0.62 µgDNA/cm2). Taken together, this study showed type of diffuser membrane biofilms had no effects on extraction efficiency, but low DNA concentrations reduced extraction performance.

Fate and Toxicity of Zinc Oxide Nanomaterial in Municipal Wastewaters.

The production of zinc nanomaterial has increased significantly over the past several years and, as a result, nanoparticles have navigated their way into wastewater streams. The transportation and toxicity of zinc nanomaterial within the wastewater treatment processes is not well known. In this study, the zinc nanomaterial and its fate were characterized in an activated sludge treatment process. The tests performed included batch studies to evaluate abiotic and biotic removal, toxicity studies to evaluate inhibition to coliform and nitrifying bacteria, and bioreactor studies to evaluate impact on operating parameters. Stock solutions of zinc nanomaterial varied in size from 50 to 500 nm, but when added to an activated sludge solution, the nanoparticles agglomerated to larger sizes such that more than 60% of the zinc nanomaterial settled out of solution. However, when ionic zinc was added to activated sludge, more than 60% of the ionic zinc remained in suspension. It is likely that the ionic strength of the wastewater influenced the aggregation of the nanomaterial. Differences in the extent of removal between ionic and nano zinc species indicate that the mechanisms governing their removal are different. Toxicity analysis showed that zinc nanomaterial did not inhibit growth of coliform and ammonia oxidizing bacteria. However, ionic zinc inhibited the growth of both the coliform and ammonia oxidizing bacteria. Bioreactors were set up using activated sludge that was collected from a local treatment plant operating only in carbon oxidation mode. The treatment plant was operated at an SRT of 1.2 days and an MLSS of 650 mg/L. Several key parameters (COD, MLSS, pH) in the bioreactors were monitored through a 7-day incubation period, but showed no significant changes due to the addition of nano or ionic zinc. It is possible that the toxicity of zinc nanomaterial was not observed in these experiments because the nanomaterial agglomerated and settled out of solution.

Modelling the link amongst fine-pore diffuser fouling, oxygen transfer efficiency, and aeration energy intensity.

This research systematically studied the behavior of aeration diffuser efficiency over time, and its relation to the energy usage per diffuser. Twelve diffusers were selected for a one year fouling study. Comprehensive aeration efficiency projections were carried out in two WRRFs with different influent rates, and the influence of operating conditions on aeration diffusers' performance was demonstrated. This study showed that the initial energy use, during the first year of operation, of those aeration diffusers located in high rate systems (with solids retention time - SRT-less than 2 days) increased more than 20% in comparison to the conventional systems (2 > SRT). Diffusers operating for three years in conventional systems presented the same fouling characteristics as those deployed in high rate processes for less than 15 months. A new procedure was developed to accurately project energy consumption on aeration diffusers; including the impacts of operation conditions, such SRT and organic loading rate, on specific aeration diffusers materials (i.e. silicone, polyurethane, EPDM, ceramic). Furthermore, it considers the microbial colonization dynamics, which successfully correlated with the increase of energy consumption (r2:0.82 ± 7). The presented energy model projected the energy costs and the potential savings for the diffusers after three years in operation in different operating conditions. Whereas the most efficient diffusers provided potential costs spanning from 4900 USD/Month for a small plant (20 MGD, or 74,500 m3/d) up to 24,500 USD/Month for a large plant (100 MGD, or 375,000 m3/d), other diffusers presenting less efficiency provided spans from 18,000USD/Month for a small plant to 90,000 USD/Month for large plants. The aim of this methodology is to help utilities gain more insight into process mechanisms and design better energy efficiency strategies at existing facilities to reduce energy consumption.

A survey of biofilms on wastewater aeration diffusers suggests bacterial community composition and function vary by substrate type and time.

Aeration diffusers in wastewater treatment plants generate air bubbles that promote mixing, distribution of dissolved oxygen, and microbial processing of dissolved and suspended matter in bulk solution. Biofouling of diffusers represents a significant problem to wastewater treatment plants because biofilms decrease oxygen transfer efficiency and increase backpressure on the blower. To better understand biofouling, we conducted a pilot study to survey the bacterial community composition and function of biofilms on different diffuser substrates and compare them to those in the bulk solution. DNA was extracted from the surface of ethylene-propylene-diene monomer (EPDM), polyurethane, and silicone diffusers operated for 15 months in a municipal treatment plant and sampled at 3 and 9 months. The bacterial community composition and function of the biofilms and bulk solution were determined by amplifying the 16S rRNA genes and pyrosequencing the amplicons and raw metagenomic DNA. The ordination plots and dendrograms of the 16S rRNA and functional genes showed that while the bacterial community composition and function of the bulk solution was independent of sampling time, the composition and function of the biofilms differed by diffuser type and testing time. For the EPDM and silicone diffusers, the biofilm communities were more similar in composition to the bulk solution at 3 months than 9 months. In contrast, the bacteria on the polyurethane diffusers were more dissimilar to the bulk solution at 3 months than 9 months. Taken together, the survey showed that the community composition and function of bacterial biofilms depend on the diffuser substrate and testing time, which warrants further elucidation.

Raffinose, a plant galactoside, inhibits Pseudomonas aeruginosa biofilm formation via binding to LecA and decreasing cellular cyclic diguanylate levels.

Biofilm formation on biotic or abiotic surfaces has unwanted consequences in medical, clinical, and industrial settings. Treatments with antibiotics or biocides are often ineffective in eradicating biofilms. Promising alternatives to conventional agents are biofilm-inhibiting compounds regulating biofilm development without toxicity to growth. Here, we screened a biofilm inhibitor, raffinose, derived from ginger. Raffinose, a galactotrisaccharide, showed efficient biofilm inhibition of Pseudomonas aeruginosa without impairing its growth. Raffinose also affected various phenotypes such as colony morphology, matrix formation, and swarming motility. Binding of raffinose to a carbohydrate-binding protein called LecA was the cause of biofilm inhibition and altered phenotypes. Furthermore, raffinose reduced the concentration of the second messenger, cyclic diguanylate (c-di-GMP), by increased activity of a c-di-GMP specific phosphodiesterase. The ability of raffinose to inhibit P. aeruginosa biofilm formation and its molecular mechanism opens new possibilities for pharmacological and industrial applications.

Linking biofilm growth to fouling and aeration performance of fine-pore diffuser in activated sludge.

Aeration is commonly identified as the largest contributor to process energy needs in the treatment of wastewater and therefore garners significant focus in reducing energy use. Fine-pore diffusers are the most common aeration system in municipal wastewater treatment. These diffusers are subject to fouling and scaling, resulting in loss in transfer efficiency as biofilms form and change material properties producing larger bubbles, hindering mass transfer and contributing to increased plant energy costs. This research establishes a direct correlation and apparent mechanistic link between biofilm DNA concentration and reduced aeration efficiency caused by biofilm fouling. Although the connection between biofilm growth and fouling has been implicit in discussions of diffuser fouling for many years, this research provides measured quantitative connection between the extent of biofouling and reduced diffuser efficiency. This was clearly established by studying systematically the deterioration of aeration diffusers efficiency during a 1.5 year period, concurrently with the microbiological study of the biofilm fouling in order to understand the major factors contributing to diffuser fouling. The six different diffuser technologies analyzed in this paper included four different materials which were ethylene-propylene-diene monomer (EPDM), polyurethane, silicone and ceramic. While all diffusers foul eventually, some novel materials exhibited fouling resistance. The material type played a major role in determining the biofilm characteristics (i.e., growth rate, composition, and microbial density) which directly affected the rate and intensity at what the diffusers were fouled, whereas diffuser geometry exerted little influence. Overall, a high correlation between the increase in biofilm DNA and the decrease in αF was evident (CV < 14.0 ± 2.0%). By linking bacterial growth with aeration efficiency, the research was able to show quantitatively the causal connection between bacterial fouling and energy wastage during aeration.

Identification and quantification of Thiothrix eikelboomii using qPCR for early detection of bulking incidents in a full-scale water reclamation plant.

This study found that the ratio of Thiothrix eikelboomii to total bacterial concentrations (TH/TB) (%) was a better indicator of bulking incidents affecting effluent quality compared to absolute T. eikelboomii abundance alone. This was determined using a genus-specific Thiothrix quantitative PCR primer and probe set, which was developed in this study to monitor specific Thiothrix populations over a 1-year period. T. eikelboomii was identified as the source of bulking incidents based on sequencing of the 16S rRNA gene at a nitrifying-denitrifying wastewater treatment plant. Peak T. eikelboomii concentrations observed in March, April, and July 2009 were 2.32 × 10(10), 2.64 × 10(10), and 1.84 × 10(10) cells/l, respectively. The highest fraction of T. eikelboomii to total bacterial population was measured at 0.24% in March, and a ratio >0.19% caused increases of suspended solids and biochemical oxygen demand in the secondary effluent. Additionally, food/mass ratios, dissolved oxygen concentrations in the anoxic selector, and ammonium ion concentrations in the primary effluent were three parameters displaying statistically significant correlations (r = 0.40, r = 0.50, and r = 0.32, respectively) to Thiothrix spp. abundance in an aeration tank. No bulking events caused by T. eikelboomii occurred when the dissolved oxygen concentrations in the anoxic selector was maintained at lower than 0.12 mg/l and the TH/TB ratios were <0.10%.

Interaction of operational and physicochemical factors leading to Gordonia amarae-like foaming in an incompletely nitrifying activated sludge plant.

The overgrowth of Gordonia amarae-like bacteria in the mixed liquor of an incompletely nitrifying water reclamation plant was inversely correlated with temperature (r = -0.78; P < 0.005) and positively correlated with the solids retention time (SRT) obtained a week prior to sampling (r = 0.67; P < 0.005). Drops followed by spikes in the food-to-mass ratio (0.18 to 0.52) and biochemical oxygen demand concentrations in primary effluent (94 to 298 mg liter(-1)) occurred at the initiation of G. amarae-like bacterial growth. The total bacterial concentration did not increase as concentrations of G. amarae-like cells increased, but total bacterial cell concentrations fluctuated in a manner similar to that of G. amarae-like bacteria in the pseudo-steady state. The ammonium ion removal rate (percent) was inversely related to G. amarae-like cell concentrations during accelerated growth and washout phases. The dissolved oxygen concentration decreased as the G. amarae-like cell concentration decreased. The concentrations of G. amarae-like cells peaked (2.47 × 10(9) cells liter(-1)) approximately 1.5 months prior to foaming. Foaming occurred during the late pseudo-steady-state phase, when temperature declines reversed. These findings suggested that temperature changes triggered operational and physicochemical changes favorable to the growth of G. amarae-like bacteria. Fine-scale quantitative PCR (qPCR) monitoring at weekly intervals allowed a better understanding of the factors affecting this organism and indicated that frequent sampling was required to obtain statistical significance with factors changing as the concentrations of this organism increased. Furthermore, the early identification of G. amarae-like cells when they are confined to mixed liquor (10(7) cells liter(-1)) allows management strategies to prevent foaming.

Evaluation of nanocopper removal and toxicity in municipal wastewaters.

Bench scale studies were performed to evaluate removal and toxicity of copper nanoparticles (CuNPs) and copper ions in activated sludge biomass. The data indicated that, under the test conditions, copper nanoparticles were removed more effectively (∼95%) than copper ions (30-70%) from the wastewater. Mechanisms of CuNP removal were further investigated by equilibrating CuNP and copper ion in activated sludge filtrate (0.45 µm). The predominant mechanisms of copper removal appear to be aggregation and settling (CuNP) or precipitation (copper ion) rather than biosorption. Most probable number (MPN) test data indicated that addition of 10 mg/L of copper ion was toxic to both coliform and ammonia oxidizing bacteria in the wastewater while no inhibitory effects were observed with the addition of the same amount of copper nanoparticles. Respirometry data indicated a 55% decrease in respiration rate when 10 mg/L ionic copper was added. However, no significant decrease in respiration rate was observed in the presence of copper nanoparticles. The toxicity of copper to activated sludge microorganisms appears to be a function of the concentration and characteristics of copper remaining in solution/suspension.

Influence of physicochemical and operational parameters on Nitrobacter and Nitrospira communities in an aerobic activated sludge bioreactor.

To understand how to optimize performance of a partially nitrifying plant, the dynamics of Nitrospira and Nitrobacter abundance were studied over a 1 year period using quantitative polymerase chain reaction (qPCR) and their relative contributions to nitrite oxidation assessed including the affects of temperature and dissolved oxygen (DO). Correlation coefficients linking shifts in the community composition of nitrite-oxidizing bacteria (NOB) to operational or environmental variables indicated Nitrospira was significantly and negatively correlated to nitrite concentrations (r = -0.45, P < 0.01) and DO (r = -0.46, P < 0.01), while temperature showed a strong positive correlation (r = 0.59, P < 0.0001). However, the Nitrobacter portion of the total NOB populations showed a positive correlations with DO (r = 0.38, P < 0.01) and hydraulic retention time (HRT) (r = 0.33, P < 0.05), as well as being negatively correlated with temperature (r = -0.49, P < 0.001) suggesting specific niche adaptations within the NOB community. Nitrospira was dominant being better adapted to the low DO and shorter sludge retention times (SRT) of this plant, while Nitrobacter increased in abundance during the winter months, when temperatures were lower and DO concentrations higher. Principal component analysis (PCA) results supported these findings by the close proximity of Nitrospira and temperature biplots of PC1 and PC2 as well as grouping Nitrobacter, NO(2)(-)-N, HRT, and DO in the loadings together. The clustering of samples from specific dates also exhibited a strong seasonality.

Classification and regression tree (CART) analysis for indicator bacterial concentration prediction for a Californian coastal area.

The study used existing indicator bacterial data and a number of physicochemical parameters that can be measured instantaneously to determine if a decision tree approach, especially classification and regression tree, could be used to predict bacterial concentrations in timely manner for beach closure management. Each indicator bacteria showed different tree structures and each had its own significant variables; Dissolved oxygen played an important role for both total coliform and fecal coliform and turbidity was the most important factor to predict concentrations of enterococci for decision tree approaches. Root mean squared error stayed between 5 and 6.5% of the average values of observations; RMSEs from each simulation, 0.25 for total coliform, 0.31 for fecal coliform, and 0.29 for enterococci. Estimations from tree structures would be regarded as a good representation of the actual data. In addition to results of the objective function, RMSE, 77.5% of actual value fell into the 95% of confidence interval of estimations for total coliform concentrations, 60% for fecal coliform concentrations, and 62.5% for enterococci concentrations. The approach showed reliable estimations for the majority of the data processed, although the method did not portray low concentrations of bacteria as well.

Identification and application of physical and chemical parameters to predict indicator bacterial concentration in a small Californian creek.

This study of Aliso Creek in California aimed to identify physical and chemical parameters that could be measured instantly to be used in a model to serve as surrogates for indicator bacterial concentrations during dry season flow. In this study, a new data smoothing technique and ranking/categorizing analysis was used to reduce variation to allow better delineation of the relationships between adopted variables and concentrations of indicator bacteria. The ranking/categorizing approach clarified overall trends between physico-chemical data and the indicators and suggested sources of the bacteria. This study also applied a principle component regression model to the data. Although the model was promising for predicting concentrations of total and fecal coliforms, it was somewhat weaker in predicting enteroccocci.

Development of a quantitative PCR method to differentiate between viable and nonviable bacteria in environmental water samples.

Ethidium monoazide bromide (EMA) treatment of pure culture and environmental waters at low concentrations (1.0-7.5 microg/ml) indicated effective enumeration of viable and viable but nonculturable Escherichia coli in pure cultures, creek waters, and secondary activated sludge effluent samples by quantitative polymerase chain reaction (qPCR) amplification of the uidA and fliC gene targets at turbidity values < 10 NTU. However, EMA treatment was not effective in primary clarifier and secondary trickling filter effluents where turbidities were > or = 10 NTU. In viable pure cultures, rapidly dividing and senescent cells were most affected by increasing EMA concentrations. Amplification of heat-killed pure bacterial cultures decreased 4 to 6 logs depending on EMA concentration and culture age. The greatest difference was observed in 5-h cultures using 7.5 microg/ml EMA. Turbidity (> or = 100 NTU) in environmental samples inhibited EMA effectiveness on viability discrimination. Enumeration of E. coli in certain wastewaters using EMA-qPCR was similar to culture suggesting that EMA treatment could be incorporated into qPCR assays for the quantification of viable bacteria increasing assay time no more than 30 min. Our results indicate that EMA can be used in routine qPCR assays, but optimum conditions for exposure must be identified for each sample type due to sample matrix effects such as turbidity.

Relationship among growth parameters for Clostridium butyricum, hydA gene expression, and biohydrogen production in a sucrose-supplemented batch reactor.

This study was undertaken to identify the relationship between the performance of dark H2 fermentation and expression of the key functional gene (i.e., hydrogenase gene) involved in the bioH2 production process. Clostridium butyricum CGS5 isolated from anaerobic sewage sludge was used as the model strain for this study. Copy number of the hydrogenase gene (hydA) and mRNA transcripts (cDNA hydA) (after amplification) and the total DNA and RNA (before amplification) were measured over the course of the growth of strain CGS5. Cell concentration was also determined by optical density and converted to dry weight. After amplification, the hydA gene increased 1,500-fold during late exponential growth phase after normalization to the copy number at time 0, and cDNA from mRNA transcripts of hydA also increased 500-fold after normalization. mRNA transcripts of hydA lagged behind the increase of total DNA and RNA, and increases in hydA more closely mimicked those of total DNA. Increases in both of these parameters corresponded with hydrogen production. Transcripts of 16s ribosomal RNA reached a maximum value earlier (38 h) than did those of hydA (47 h). All molecular characteristics matched those for sucrose utilization, growth, and hydrogen production. These experiments indicated that transcription as measured by cDNA can be related to hydrogen production and possesses the potential to be used as tool for process control.

Improving PCR and qPCR detection of hydrogenase A (hydA) associated with Clostridia in pure cultures and environmental sludges using bovine serum albumin.

Detection of hydA genes of Clostridia spp. using degenerative and species specific primers for C. butyricum were optimized by the addition of bovine serum albumin (BSA) to polymerase chain reaction (PCR) and quantitative PCR (qPCR) reactions. BSA concentrations ranging from 100 to 400 ng/microl were examined using pure cultures and a variety of environmental samples as test targets. A BSA concentration of 100 ng/microl, which is lower than previously reported in the literature, was found to be most effective in improving the detection limit. The brightness of amplicons with 100 ng/mul BSA increased in ethidium bromide-treated gels, the minimum detection limit with BSA was at least one log greater, and cycle threshold (C(T)) values were lower than without BSA in qPCR indicating improved detection of target deoxyribonucleic acid for most samples tested. Although amplicon visualization was improved at BSA concentrations greater than or equal to 100 ng/microl, gene copy numbers detected by qPCR were less, C(T) values were increased, and T(m) values were altered. SYBR Green dissociation curves of qPCR products of DNA from pure culture or sludge samples showed that BSA at 100 ng/microl reduced the variability of peak areas and T(m) values.

Microbial source tracking in a small southern California urban watershed indicates wild animals and growth as the source of fecal bacteria.

Three independent microbial source tracking (MST) methods were applied to a small urban subwatershed in Orange County, California. Fifty-seven water samples collected over summer 2002 were analyzed for human adenovirus and enterovirus. Enterococci and E. coli were isolated for antibiotic resistance analysis (ARA) and for PCR identification of human- and animal-specific toxin genes, respectively. All water samples were PCR negative for human enteroviruses and E. coli human-specific toxin gene. E. coli toxin markers revealed the presence of toxin genes specific to bird, rabbit, and cow. Enterococci ARA results supported this conclusion and indicated that fecal bacteria from bird and wild animal feces as well as soil were the predominant source found in the watershed. An E. coli, isolated from the watershed and inoculated back into the heat-sterilized storm drain water, increased 4 log units within 6 days. Collectively, these results suggest that bird and wild animal feces, soil amendments, and/or fecal coliform growth in the storm drain are the major contributors to the fecal bacterial pollution in downstream areas. However, human adenoviruses were detected on two occasions. Fecal bacterial concentrations were not elevated on these two occasions, suggesting that the elevated levels of fecal indicator bacteria in this small watershed could be unrelated to the source of human adenovirus.

Estimating the economic burden from illnesses associated with recreational coastal water pollution--a case study in Orange County, California.

A cost-of-illness framework was applied to health and income data to quantify the health burden from illnesses associated with exposure to polluted recreational marine waters. Using data on illness severity due to exposure to polluted coastal water and estimates of mean annual salaries and medical costs (adjusted to 2001 values) for residents of Orange County, California, we estimated that the economic burden per gastrointestinal illness (GI) amounts to 36.58 dollars, the burden per acute respiratory disease is 76.76 dollars, the burden per ear ailment is 37.86 dollars, and the burden per eye ailment is 27.31 dollars. These costs can become a substantial public health burden when millions of exposures per year to polluted coastal waters result in hundreds of thousands of illnesses. For example, exposures to polluted waters at Orange County's Newport and Huntington Beaches were estimated to generate an average of 36,778 GI episodes per year. At this GI illness rate, one can also expect that approximately 38,000 more illness episodes occurred per year of other types, including respiratory, eye, and ear infections. The combination of excess illnesses associated with coastal water pollution resulted in a cumulative public health burden of 3.3 million dollars per year for these two beaches. This paper introduces a public health cost variable that can be applied in cost-benefit analyses when evaluating pollution abatement strategies.

Health effects associated with recreational coastal water use: urban versus rural California.

We compared rates of reported health symptoms among surfers in urban North Orange County (NOC) and rural Santa Cruz County (SCC), California, during 2 winters (1998 and 1999) to determine whether symptoms were associated with exposure to urban runoff. NOC participants reported almost twice as many symptoms as SCC participants during the 1998 winter. In both study years, risk increased across symptom categories by an average of 10% for each 2.5 hours of weekly water exposure. Our findings suggest that discharging untreated urban runoff onto public beaches can pose health risks.