Zinc Pollution Potential of Consumer Battery Litter

Consumer batteries in urban litter can be significant sources of storm-water pollution. Recent studies have reported annual urban battery litter rates as high as 215 batteries per hectare of pavement and 0.4 batteries per meter of street curb. On average, 75% of these batteries are leaking or have already discharged their internal reactants. However, many battery sizes, brands, and power chemistries are littered and this diversity makes it difficult to quantify their cumulative pollution potential. The amount of zinc released from AA size alkaline and zinc chloride/zinc carbon (ZnCl/ZnC) batteries which account for approximately 90% of urban battery litter is examined. Results are presented for batch rupture release extractions of 52 alkaline battery products yielding zinc releases of 20–40 mg/L and 57 ZnCl/ZnC products yielding zinc releases of 400–1,400 mg/L. Results of continuous flow column extractions are also presented to gauge releases following initial battery rupture. Disassembly analyses are used to bound the total zinc release potential of common battery products. Results indicate that ZnCl/ZnC batteries release more zinc when they are first ruptured, but if deterioration is complete, alkaline batteries can release approximately 25% more zinc. Therefore, the relative importance of these two classes of batteries depends on site-specific factors such as the proportion of each in litter, battery deterioration rates, and the length of time that battery litter remains unremediated by maintenance.     

Urban Battery Litter

Consumer batteries littered in urban environments are generally littered on pavements. These batteries rapidly deteriorate by several physical and chemical mechanisms that breach their structural integrity and release a host of environmentally significant pollutants (Ag, Ba, Cd, Cr, Cu, Hg, Li, Mn, Ni, Pb, Ti, Zn) to storm-water runoff. Research on urban battery litter began at Case Western Reserve University in the summer of 2001. This paper presents much of what is currently known about the occurrence of urban battery litter. Data are presented on the number, type, and condition of over 6,100 littered batteries collected in field surveys conducted in urban areas around Cleveland. Methods are presented for estimating battery litter rates and for characterizing the size, structure, internal chemistry, deterioration status, life expectancy, and contaminant release potential of urban battery litter. Results from field study sites demonstrate that at “hot spot” locations, battery litter can be a significant source of contamination. Annual litter rates as high as 215?batteries/ha (nearly 90/acre) of parking lot pavement and 0.4?batteries/m of street curb (one battery for every 8?ft. of curb) have been measured. At some locations the Zn mass loading from batteries approaches 1?kg/ha and could be the most significant source of pavement-related Zn released to urban storm-water runoff.     

New Approach to Evaluate Pollutant Removal by Storm-Water Treatment Devices

A methodology was developed to monitor and evaluate the removal of solids and associated constituents by a nutrient separating baffle box (NSBB) storm-water treatment device treating runoff from a 4.3 ha (10.6 acre) residential watershed discharging into the Indian River Lagoon, Florida. The NSBB was monitored over a 359-day time period using autosamplers to quantify water column removal during runoff events, and by quantifying and analyzing solids that accumulated within the NSBB. Flow composited influent and effluent samples were collected to represent water column performance. Event mean concentration (EMC) reduction was moderate (mean: 17%) and variable (range: ?39 to 68%) for suspended solids, and negative for nitrogen, phosphorus, fecal coliforms chromium, and copper. The mass of solids that accumulated in bottom chambers and in a strainer screen was quantified and analyzed for nitrogen, phosphorus, heavy metals, and polycyclic aromatic hydrocarbons. A quantitative evaluative framework was devised to estimate the total pollutant mass removal by NSBB, which consisted of the summation of the separately calculated mass removals for water column, bottom chamber material, and strainer screen material. The water column accounted for only 4% of total solids that accumulated in the NSBB, which was equally divided between bottom chamber and strainer screen. Removal of nitrogen, phosphorus, and metals could be accounted for only by considering mass accumulations. Results suggest that overall assessment of pollutant removal by NSBB must be cognizant of the materials not captured by typical autosamplers: larger size sediment particles, large floating and suspended matter, and the pollutants associated with these materials. Using water column EMCs as the sole measure of performance significantly underestimated loading reduction of storm-water constituents by the NSBB. The monitoring and evaluative methodology applied to the NSBB may be applicable to load reduction evaluations for other storm-water treatment devices with a similar function.     

Modeling Escherichia Coli and Its Sources in an Urban Bayou with Hydrologic Simulation Program—FORTRAN

Bacterial levels in Buffalo Bayou in Houston commonly exceed contact recreation standards. Potential sources of bacteria include wastewater treatment plants, sanitary sewer overflows, septic systems, wet and dry nonpoint-source discharges via direct runoff and pipes, direct deposition, and sediment. A water-quality model in the Hydrologic Simulation Program—FORTRAN (HSPF) was calibrated and validated for hydrology, sediment, and Escherichia coli and subsequently used to evaluate the impacts of the bacterial sources in the watershed. In addition, simple estimates of bacterial loads were calculated along with source evaluations from load duration curves. Load reductions based upon the simple estimates indicated that water-quality standards were met by reducing dry-weather indicator bacterial loads by 69% and wet-weather loads by 98%. When these load reductions were implemented in the HSPF model, however, standards were not met under dry-weather conditions. Residual nonpoint-source loading was found to cause the discrepancy between simple load estimate calculations and the developed water-quality model. This paper demonstrates that runoff can play a significant role in maintaining high levels of bacteria under all flow conditions and that understanding the temporal variations in bacterial source loading is critical to ensure that load reductions will achieve water-quality standards.     

Impact of Traffic Load Cycles on Urban Battery Litter

Recent studies have demonstrated that the annual rates of consumer battery litter on urban pavements can be as high as 215 batteries per hectare of pavement and 0.4 batteries per meter of curb. As littered batteries deteriorate, they release components of potential environmental significance (Ag, Ba, Cd, Cr, Cu, Hg, Li, Mn, Na, Ni, Pb, Ti, Zn) and add to urban storm water contamination. However, consumer batteries come in many sizes, brands, and power chemistries, all of which may deteriorate at different rates in response to hostile physical and chemical conditions. The work presented here examines the impact of tire load cycles on battery litter. Tests were conducted on 735 individual cells representing 42 brands of AAA, AA, C, and D cell batteries. Results indicate that there are significant differences in the deterioration properties of battery brands and power chemistry types. Alkaline batteries are most resistant to deformation under tire loading. Nearly 50% survive their first tire load and about 30% survive 100 tire load cycles without rupturing. Zinc chloride/zinc carbon (ZnCl/ZnC) batteries are less resistant to deformation. Only approximately 10% survive their first load cycle unruptured. Cell size appears to have little influence on traffic-induced rupture. Based on general battery litter profiles, mass loading calculations for moderate traffic areas should assume that 70% of littered cells have experienced rupture release. This estimate should be increased to 85% for heavy traffic areas. These estimates may be refined if more detail is available on the brand and type distribution of site battery litter.     

Investigation of Boundary Shear Stress and Pollutant Detachment from Impervious Surface during Simulated Urban Storm Runoff

Pollutant detachment rates have been determined for four chloride salts during simulated urban storm runoff. Under rainfall and/or overland flow conditions, chloride mass flux was measured and related to boundary shear stress of the test surface. Washoff coefficients, presumed to depend only on pollutant characteristics, were computed based on the slopes of dimensionless mass flux versus dimensionless time plots. Washoff coefficients were found to vary among and between the chloride compounds studied. In general, higher overland flow rates produced lower boundary shear and lower washoff coefficients. The combination of simulated rainfall and overland flow resulted in an increased boundary shear and an increased washoff coefficient. An empirical washoff coefficient based on a load characteristic curve derived from an exponential washoff relationship was also computed from the runoff data and compared with the previous washoff coefficient. A linear correlation between these two washoff coefficients was observed. The magnitude of the latter coefficient under simulated rainfall was consistent with reported values obtained from field data.     

Storm Flow from First-Flush Precipitation in Stormwater Design

Regulations for mitigating nonpoint source pollution from urban areas often include a requirement for treatment of a first-flush depth of stormwater. When the stormwater treatment technology requires specification of a design flow rate, the first-flush depth must be related to a first-flush flow rate. This paper describes a methodology to determine the relation between accumulated storm depth and corresponding flow to a treatment device for small, urban watersheds. The approach uses the rational method under the assumption that the time-of-concentration is small. Intensity–frequency relations, expressed in the form of return periods and associated intensities, were determined using a partial duration frequency analysis of regionalized precipitation data. The results of the method can be used to determine the flow rate to a treatment device that will meet a specified return period for a first-flush depth. The method is demonstrated using 13 years of 15-min data from seven Massachusetts precipitation stations.     

Integrated Storm-Water Management for Watershed Sustainability

One aspect of integrated watershed management evaluates the impact of development on the local hydrologic cycle and, in particular, drinking water, wastewater, and storm-water infrastructure. Sustainable storm-water management focuses on selecting storm-water controls based on an understanding of the problems in local receiving waters that result from runoff discharges. For example, long-term problems associated with accumulations of pollutants in water bodies include sedimentation in conveyance systems and receiving waters, nuisance algal growths, inedible fish, undrinkable water, and shifts to less sensitive aquatic organisms. Short-term problems associated with high pollutant concentrations or frequent high flows (event-related) include swimming beach closures, water quality violations, property damage from increased flooding, and habitat destruction. A wide variety of individual storm-water controls usually must be combined to form a comprehensive wet weather management strategy. Unfortunately, combinations of controls are difficult to analyze. This will require new modeling techniques that can effectively evaluate a wide variety of control practices and land uses, while at the same time ensure that the flood-control objectives also are met. The results of these new models and novel techniques used for storm-water control then can be incorporated into an evaluation of the urban water cycle for a specific service area to determine whether storm-water controls can provide additional benefits such as reduction of potable water use and reduction of sanitary sewer overflow events.     

Bacteria Loads from Point and Nonpoint Sources in an Urban Watershed

A pathogen impaired watershed in Houston, Tex., was studied to assess the spatial and temporal nature of point and nonpoint bacterial load contributions. End-of-pipe sampling at wastewater treatment plant effluent and storm sewers discharging under dry weather conditions was undertaken. Relatively low concentrations of E. coli were found in wastewater treatment effluent, with a geometric mean of 5 MPN/dL, while dry weather storm sewer discharges exhibited a geometric mean concentration of 212 MPN/dL. Loads from both point and nonpoint sources of E. coli were calculated and compared to in-stream bacteria loads. Nonpoint loads were estimated using an event mean concentration approach on an annual basis. Nonpoint source (NPS) loads were the primary source of bacteria loading to the bayou. Wastewater treatment plant and dry weather storm sewer loads, however, dominated in dry weather conditions. While NPS loads remained relatively constant from headwaters to the mouth of the bayou, point source loads exhibited greater spatial variability depending on the distribution of the discharging pipes. The study points to the need for spatial and temporal considerations in managing bacterial pollution in streams.     

Variability of Escherichia coli Concentrations in an Urban Watershed in Texas

In this study, daily Escherichia coli measurements at six locations in an urban watershed in Houston, were undertaken over a period of 12 weeks, and were analyzed using time series and fractal analyses. The time series analysis revealed that the E. coli data series were nonrandom in nature and were characterized by a lack of periodicity. Shorter E. coli time series data sets (on the order of 10 days or less) exhibited a fractal structure, suggesting that micro scale time series may be fractal in nature in urban environments, a finding that has significant implications for bacteriological water quality monitoring. Although stormflow E. coli concentrations were significantly higher than baseflow levels, the range of variability in E. coli concentrations both during dry and wet weather conditions was comparable, indicating the residual impacts of rain events on bayou water quality. While other studies in the literature have shown that afternoon E. coli levels were lower than morning levels, the results from this study demonstrate the complexity of this phenomenon and its dependence on flow, turbidity, total suspended solids, temperature and the location/land use of the monitoring point (upstream or downstream and rural/urban). Spatial variability was highly correlated to land use with key differences between grassland and urban uses: urbanized sites exhibited higher overall E. coli concentrations, experienced rebound in E. coli levels during and after a rain event, exhibited no correlations between total suspended solids and E. coli, and exhibited less daily variability in bacteria concentrations.     

Compaction’s Impacts on Urban Storm-Water Infiltration

Soil infiltration is a critical component of most urban runoff models. However, it has been well documented that, during urbanization, soils are greatly modified, especially in relation to soil density. Increased soil compaction results in soils that do not behave in a manner predicted by traditional infiltration models. Laboratory and field tests were conducted to investigate detailed infiltration behavior of disturbed urban soils for a variety of soil textures and levels of compaction. The results from traditional permeability tests on several soil groups showed that, as expected, the degree of compaction greatly affected the steady-state infiltration rate. The field tests highlighted the importance of compaction on the infiltration rate of sandy soils, with minimal effect seen from antecedent moisture conditions. For the clayey soils, however, both the compaction level and antecedent moisture conditions were important in determining the steady-state infiltration rate.     

Evaluating Urban Pollutant Buildup/Wash-Off Models Using a Madison, Wisconsin Catchment

Buildup/wash-off (BUWO) models are widely used to estimate pollutant export from urban and suburban watersheds. Here, we propose that the mass of washed-off particulate during a storm event is insensitive to the time between storm events (the traditional predictor of particulate accumulation in BUWO models). Our analysis employed USGS data of total suspended solids and discharge data for nonsnow events in a 9.4-km2 suburban catchment in Madison, Wis. Kinetic energy of rainfall was calculated using National Weather Service NEXRAD radar reflectivity. A regression analysis found that storm event runoff volume and rainfall kinetic energy explained 81% of the variability in event particulate load; volume alone explained 69% of the variability in event loads. Time between storm events was not significant. Additionally, we simulated storm event particulate loads using a BUWO model and a model assuming a constant mass available for wash-off. Both models produced very similar predictions over a range of parameterizations, suggesting that buildup models could perhaps be simplified under many circumstances.     

Pollutant Removal and Peak Flow Mitigation by a Bioretention Cell in Urban Charlotte, N.C.

Bioretention is a stormwater treatment practice that has gained popularity due to its aesthetics, potential to reduce flooding, and early documented improvements to stormwater quality. A bioretention cell in an urban setting was examined in Charlotte, N.C. from 2004 to 2006. Flow-weighted, composite water quality samples were collected for 23 events and analyzed for TKN, NH4-N, NO2-3-N, TP, TSS, BOD-5, Cu, Zn, Fe, and Pb. Grab samples were collected from 19 storms for fecal coliform and 14 events for Escherichia coli (E. coli). There were significant reductions (p<0.05) in the concentrations of TN, TKN, NH4-N, BOD-5, fecal coliform, E. Coli, TSS, Cu, Zn, and Pb. Iron concentrations significantly increased (p<0.05). NO2-3-N concentrations were essentially unchanged. Efficiency ratios for TN, TKN, NH4-N, TP, and TSS were 0.32, 0.44, 0.73, 0.31, and 0.60, respectively. Fecal coliform and E. coli efficiency ratios were 0.69 and 0.71, respectively. Efficiency ratios for Zn, Cu, and Pb were 0.77, 0.54, and 0.31, respectively. Concentrations of Fe increased by 330%. The peak outflow of the bioretention cell for 16 storms with less than 42?mm of rainfall was at least 96.5% less than the peak inflow, with a mean peak flow reduction being 99%. These results indicated that in an urban environment, bioretention systems can reduce concentrations of most target pollutants, including pathogenic bacteria indicator species. Additionally, bioretention can effectively reduce peak runoff from small to midsize storm events.     

Characterizing Physicochemical Quality of Storm-Water Runoff from an Urban Area in Calgary, Alberta

Understanding storm-water runoff quality is required to develop effective urban storm-water runoff management for regions of semiarid climate. In this study, the quality of storm-water runoff from a semiarid, urban residential catchment, draining through separated storm-water sewers was investigated in 2006 and 2007. Water temperature, conductivity, pH, dissolved oxygen, and turbidity were continuously measured during 16 storm events. Storm-water runoff quality was characterized in terms of event mean values (EMVs), loads, and first flush (FF) loads and their relationships with rainfall characteristics. Discharge of total suspended solids (TSSs) is in general governed by the flow magnitude in storms and no significant relationships exist between the FF loads of TSS and rainfall intensity. The discharge of dissolved solids is independent of the flow magnitude. Strong FF effect for dissolved solids and weak FF effect for TSS were observed. This semiarid region provided no relationship between the EMVs of both TSS and conductivity and the antecedent dry period. This raises doubts on storm-water runoff being more heavily loaded with pollutants after a longer dry period in semiarid regions.     

Process Modeling of Storm-Water Flow in a Bioretention Cell

A two-dimensional variable saturated flow model was developed to simulate subsurface flow in bioretention facilities employing the Richards’ equation. Variable hydrologic performances of bioretention are evaluated using the underdrain outflow hydrographs, outflow volumes for 10 storms with various duration and depth, and flow duration curves for 25 different storms. The effects of some important design parameters and elements are tested, including media type, surrounding soils, initial water content, ratio of drainage area to bioretention surface area, and ratio of cell length to width. Model results indicate that the outflow volume via underdrain is less than the inflow; the flow peak is significantly reduced and delayed. Underdrain outflow volume from loamy sand media (with larger Ks) is larger than that from sandy clay loam media. The saturated hydraulic conductivity, storage capacity, and exfiltration into surrounding soils contribute to the hydrologic performance of a bioretention cell. Initial media storage capacity is affected by the hydraulic properties of media soils, initial water content, and bioretention surface area. The exfiltration volume is determined by the surrounding soil type and exfiltration area, dominated by flow through the bottom of the media.     

Trace Metal Pollutant Load in Urban Runoff from a Southern California Watershed

In order to implement efficient and effective management strategies for coastal water quality in Southern California, it is important to consider the relative pollutant contributions from urban dry-weather flow (DWF) and wet-weather flow (WWF). This study uses both historical flow coupled with water quality monitoring data and computer modeling to characterize the annual DWF and WWF discharges from an urban catchment in Los Angeles, Calif. The DWF and WWF pollutant loading of the trace metals copper, lead, nickel, and chromium for 6 water years dating from 1991 to 1996 is predicted. The results indicate that DWF contributes a considerable amount of flow and pollutants. Approximately, 9–25% of the total annual Ballona Creek flow volume is DWF. The simulations indicate DWF accounts for 54, 19, 33, and 44% of the average annual load of total chromium, copper, lead, and nickel, respectively. In the dry season, the simulations indicate DWF accounts for 89, 59, 58, and 90% of the load of total chromium, copper, lead, and nickel, respectively. This research suggests DWF controls may be an important part of pollution mitigation plans for urban stormwater drainage systems in Southern California.     

Predictive Modeling of Storm-Water Runoff Quantity and Quality for a Large Urban Watershed

A predictive model for storm-water runoff was implemented on a GIS platform based on the unit area loading method and Browne’s empirical relation for soil characteristics for the Upper Ballona Creek Watershed in Los Angeles. The heterogeneity of the watershed was quantified by dividing it into many small subareas and applying lumped parameters for each. Characterization of total pollutant load by land-use types to total loads was achieved through zeroth-order regularization and limited memory Broyden–Fletcher–Goldfarb–Shanno bound constrained optimization techniques. Relative form was used in the objective function to compensate for strong contributions of high magnitude variables. Model predictions showed reasonable agreement with pollutant loadings, using Zn as an example, measured at the mass emission site at watershed mouth. The predicted runoff volumes using the developed quantity model were in good agreement with the data and had R2 of 0.86. The RMS error of the quality model was 9?kg, which is low compared to the mean discharge of 77?kg/event.     

Water Quality Improvement through Reductions of Pollutant Loads Using Bioretention

As an increasingly adopted storm-water best management practice (BMP) to remedy hydrology and water quality impairment from urban development, bioretention facilities need rigorous investigation to quantify performance benefits and to allow design improvements. This study examines water quality improvements [total arsenic, total cadmium, chloride, total chromium, total and dissolved copper, E. coli, fecal coliform, lead, mercury, nitrogen species, oil and grease, phosphorus, total organic carbon (TOC), total suspended solids, and total zinc] via monitoring for a 15-month period at two bioretention cells in Maryland. Both bioretention cells effectively removed suspended solids, lead, and zinc from runoff through concentration reduction. Runoff volume reduction promotes pollutant mass removal and links BMP water quality benefits with hydrologic performance. From a load perspective (kg/ha?year), all but TOC at one cell showed pollutant reduction. Bioretention effluents exhibited good water quality for all significant pollutants except for nitrate, copper, and phosphorus in one cell, the latter two of which may be attributed to media organic matter dissolution. Copper dissolved/particulate analyses showed that significant changes in copper speciation behavior result from transport through the bioretention media.     

Sampling Issues in Urban Runoff Monitoring Programs: Composite versus Grab

Storm-water monitoring generally uses flow-weighted automatic composite samplers to collect a representative sample of an entire storm event. Automatic samplers are convenient but unfortunately they can be expensive, especially for temporary sampling needs or for short-term research projects. An alternative method is to use a series of grab samples. This paper examines the accuracy of event mean concentrations (EMCs) and mass first flush ratios calculated from a finite number of grab samples, and compares them to results from flow-weighted automatic samples. Both sampling techniques were evaluated using data collected from a three-year investigation of three highway sites. A large number of grab samples is needed to approach the accuracy and precision of flow weighted composite samples, and 30 grab samples per storm event generally estimated the EMCs within 20% average error. To detect a first flush, it is necessary to take even more grab samples or to adjust the timing of the sample collection toward the beginning of the storm. The superiority of automatic sampling for estimating EMCs for constituents compatible with automatic sampling is demonstrated.     

Pollutant Mass Flushing Characterization of Highway Stormwater Runoff from an Ultra-Urban Area

Water quality of highway stormwater runoff from an ultra-urban area was characterized by determining the event mean concentration (EMC) for several pollutants and by evaluating pollutant flushing. Thirty-two storm events were monitored between June 2002 and October 2003. Mean EMCs in mg/L were 0.035, 0.11, 0.22, 1.18, 420, 3.4, 0.14, 1.0, and 0.56 for Cd, Cu, Pb, Zn, total suspended solids (TSS), total Kjeldahl nitrogen (TKN), NO2–N, NO3–N, and TP. First flush as defined by flushing of 50% of the total pollutant mass load in the first 25% of the event runoff volume occurred in 33% of the storm events for NO2?, 27% for TP, 22% for NO3? and TKN, 21% for Cu, 17% for TSS, 14% for Zn, and 13% for Pb. Median values for the mass flushed in the first 25% of runoff volume were greater than the mass flushed in any 25% portion beyond the first for all pollutants. The mass in later 25% volume portions were greater than in the first 25% volume in at least 17% of the events for all pollutants, indicating that a significant amount of the pollutant load can be contained in later portions of the runoff volume. Nonetheless, management of the first 1.3?mm (1/2?in.) of runoff was able to capture 81–86% of the total pollutant mass.