Assessment of the water self-purification capacity on a river affected by organic pollution: application of chemometrics in spatial and temporal variations

Water pollution caused by organic matter is a major global problem which requires continuous evaluation. Multivariate statistical analysis was applied to assess spatial and temporal changes caused by natural and anthropogenic phenomena along Potrero de los Funes River. Cluster analysis (CA), principal component analysis (PCA) and analysis of variance (ANOVA) were applied to a data set collected throughout a period of 3 years (2010–2012), which monitored 22 physical, chemical and biological parameters. Content of dissolved oxygen in water and biochemical oxygen demand in a watercourse are indicators of pollution caused by organic matter. For this reason, the Streeter-Phelps model was used to evaluate the water self-purification capacity. Hierarchical cluster analysis grouped the sampling sites based on the similarity of water quality characteristics. PCA resulted in two latent factors explaining 75.2 and 17.6 % of the total variance in water quality data sets. Multidimensional ANOVA suggested that organic pollution is mainly due to domestic wastewater run-offs and anthropogenic influence as a consequence of increasing urbanization and tourist influx over the last years. Besides, Streeter-Phelps parameters showed a low reaeration capacity before dam with low concentration of dissolved oxygen. Furthermore, self-purification capacity loss was correlated with the decrease of the Benthic Index. This measurement suggested that biological samplings complement the physical-chemical analysis of water quality.     

Factors affecting degradation of dimethyl sulfoxide (DMSO) by fluidized-bed Fenton process

In this study, the target compound is dimethyl sulfoxide (DMSO), which is used as a photoresist stripping solvent in the semiconductor and thin-film transistor liquid crystal display (TFT-LCD) manufacturing processes. The effects of the operating parameters (pH, Fe²⁺ and H₂O₂ concentrations) on the degradation of DMSO in the fluidized-bed Fenton process were examined. This study used the Box-Behnken design (BBD) to investigate the optimum conditions of DMSO degradation. The highest DMSO removal was 98 % for pH 3, when the H₂O₂ to Fe²⁺ molar ratio was 12. At pH 2 and 4, the highest DMSO removal was 82 %, when the H₂O₂ to Fe²⁺ molar ratio was 6.5. The correlation of DMSO removal showed that the effect of the parameters on DMSO removal followed the order Fe²⁺?>?H₂O₂?>?pH. From the BBD prediction, the optimum conditions were pH 3, 5 mM of Fe²⁺, and 60 mM of H₂O₂. The difference between the experimental value (98 %) and the predicted value (96 %) was not significant. The removal efficiencies of DMSO, chemical oxygen demand (COD), total organic carbon (TOC), and iron in the fluidized-bed Fenton process were higher than those in the traditional Fenton process.     

Spectrofluorimetric study of the ageing of mixtions used in the gildings of mediaeval wall paintings

Introduction  

In the Middle Ages, we could find gildings on mural paintings. Gold, silver or tin leaves were applied according to distemper or mixtion technique. For the first one, a binder as glue is necessary, and for the second, a lipidic binder is used to stick the metallic leaf. Studies of gildings materials characterization show that the mixtion technique, with a mordant, is the most common. Linseed oil seems to be the binder used. It is always mixed with a siccative agent as lead. Because of bad conditions of conservation, the gildings do not resist anymore, only remain traces of metal or the adhesive under-layer. Thanks to the binder fluorescence, we can nowadays detect ancient gildings.     

Distribution,possible sources,and health risk assessment of SVOC pollution in small streams in Pearl River Delta,China

The pollution levels of typical semivolatile organic compounds (SVOCs) consisting of 15 polycyclic aromatic hydrocarbons (PAHs), 20 organic chlorinated pesticides (OCPs), and 15 phthalate esters (PAEs) were investigated in small rivers running through the flourishing cities in Pearl River Delta region, China. The concentrations of ∑15PAHs were 2.0–48 ng/L and 29–1.2?×?10³ ng/g in the water and sediment samples, respectively. The ∑20OCPs were 6.6–57 ng/L and 9.3–6.0?×?10² ng/g in the water and sediment samples, respectively. The concentrations of ∑15PAEs were much higher both in the water and sediments. The partition process of the detected SVOCs between the water and sediment did not reach the equilibrium state at most of the sites when sampling. The combustion of petroleum products and coal was the major source of the detected PAHs. The OCPs were mainly historical residue, whereas the new inputs of dichlorodiphenyltrichloroethane (DDT), chlordane, and endosulfan were possible at several sites. The industrial and domestic sewage were the major source for the PAEs; storm water runoff accelerated the input of PAEs. No chronic risk of the SVOCs was identified by a health risk assessment through daily water consumption, except for the ∑20OCPs that might cause cancer at several sites. Nevertheless, the integrated health risk of the SVOCs should not be neglected and need intensive investigations.     

Microwave Process for Volatile Organic Compound Abatement

ABSTRACT

The CHA Corporation has completed the U.S. Air Force Phase II Small Business Innovation Research program to investigate the feasibility of using a novel microwave-based process for the removal and destruction of volatile organic compounds (VOCs) in effluents from noncombustion sources, such as paint booth ventilation streams. Removal of solvents by adsorption, followed by the regeneration of saturated granular activated carbon (GAC) by microwave energy, was achieved in a single fixed-bed reactor. Microwave regeneration of the fixed-bed-saturated carbon restored the original GAC adsorption capacity. After 20 adsorption/regeneration cycles, the adsorption capacity dropped from 13.5 g methyl ethyl ketone (MEK)/100 g GAC to 12.5 g MEK/100 g GAC. During microwave regeneration of the GAC fixed bed, the concentrated desorbed paint solvent was oxidized by passing the solvent mixture through a fixed bed of an oxidation catalyst mixed with silicon carbide in a microwave reactor. A 98% oxidation efficiency was consistently achieved from the oxidation of VOCs in the microwave catalytic reactor.     

Degradation of polycyclic aromatic hydrocarbons in a coking wastewater treatment plant residual by an O3/ultraviolet fluidized bed reactor

Coking wastewater treatment plant (CWWTP) represents a typical point source of polycyclic aromatic hydrocarbons (PAHs) to the water environment and threatens the safety of drinking water in downstream regions. To enhance the removal of residual PAHs from bio-treated coking wastewater, a pilot-scale O₃/ultraviolet (UV) fluidized bed reactor (O₃/UV FBR) was designed and different operating factors including UV irradiation intensity, pH, initial concentration, contact time, and hydraulic retention time (HRT) were investigated at an ozone level of 240 g h^?1 and 25?±?3 °C. A health risk evaluation and cost analysis were also carried out under the continuous-flow mode. As far as we know, this is the first time an O₃/UV FBR has been explored for PAHs treatment. The results indicated that between 41 and 75 % of 18 target PAHs were removed in O₃/UV FBR due to synergistic effects of UV irradiation. Both increased reaction time and increased pH were beneficial for the removal of PAHs. The degradation of the target PAHs within 8 h can be well fitted by the pseudo-first-order kinetics (R ²?>?0.920). The reaction rate was also positively correlated with the initial concentrations of PAHs. The health risk assessment showed that the total amount of carcinogenic substance exposure to surface water was reduced by 0.432 g day^?1. The economic analysis showed that the O₃/UV FBR was able to remove 18 target PAHs at a cost of US$0.34 m^?3. These results suggest that O₃/UV FBR is efficient in removing residuals from CWWTP, thus reducing the accumulation of persistent pollutant released to surface water.     

Phylogenetic analysis of the microbial community in hypersaline petroleum produced water from the Campos Basin

In this work the archaea and eubacteria community of a hypersaline produced water from the Campos Basin that had been transported and discharged to an onshore storage facility was evaluated by 16S recombinant RNA (rRNA) gene sequence analysis. The produced water had a hypersaline salt content of 10 (w/v), had a carbon oxygen demand (COD) of 4,300 mg/l and contains phenol and other aromatic compounds. The high salt and COD content and the presence of toxic phenolic compounds present a problem for conventional discharge to open seawater. In previous studies, we demonstrated that the COD and phenolic content could be largely removed under aerobic conditions, without dilution, by either addition of phenol degrading Haloarchaea or the addition of nutrients alone. In this study our goal was to characterize the microbial community to gain further insight into the persistence of reservoir community members in the produced water and the potential for bioremediation of COD and toxic contaminants. Members of the archaea community were consistent with previously identified communities from mesothermic reservoirs. All identified archaea were located within the phylum Euryarchaeota, with 98 % being identified as methanogens while 2 % could not be affiliated with any known genus. Of the identified archaea, 37 % were identified as members of the strictly carbon-dioxide-reducing genus Methanoplanus and 59 % as members of the acetoclastic genus Methanosaeta. No Haloarchaea were detected, consistent with the need to add these organisms for COD and aromatic removal. Marinobacter and Halomonas dominated the eubacterial community. The presence of these genera is consistent with the ability to stimulate COD and aromatic removal with nutrient addition. In addition, anaerobic members of the phyla Thermotogae, Firmicutes, and unclassified eubacteria were identified and may represent reservoir organisms associated with the conversion hydrocarbons to methane.     

Application of the triolein-embedded cellulose acetate membrane passive sampler for monitoring of polycyclic aromatic hydrocarbons in water

Triolein-embedded cellulose acetate membrane (TECAM) can be used as a passive sampler to measure hydrophobic organic contaminants in water. Uptake constant rates (k _u ) for polycyclic aromatic hydrocarbons (PAHs) by TECAM sampling were measured under different hydrodynamic conditions. The measured k _u values were modeled to enable the quantification of time weighed average (TWA) concentrations of PAHs in the field. An empirical relationship that enables the calculation of in situ k _u values of chemicals using performance reference compounds (PRCs) was derived and its application was demonstrated in a field study. The results showed that freely dissolved concentrations of hydrophobic organic compounds (HOCs) can be accurately measured in the field using TECAM method based on empirical uptake models calibrated with PRCs.     

Oxidation of polycyclic aromatic hydrocarbons by horseradish peroxidase in water containing an organic cosolvent

Polycyclic aromatic hydrocarbons (PAHs) are environmental contaminants that are toxic, mutagenic, and carcinogenic. We investigated the horseradish peroxidase (HRP)-catalyzed oxidation of PAHs in water containing N,N-dimethylformamide. Four PAHs (anthracene, phenanthrene, pyrene, and fluoranthene) were investigated using single-PAH and mixed-PAH systems. The results provide useful information regarding the preferential oxidation of anthracene over other PAHs regardless of the reaction time, enzyme dosage, and hydrogen peroxide concentration. The removal of PAHs was found to be very strongly correlated with the ionization potential (IP), and much greater PAH oxidation was observed at a lower IP. The oxidation of anthracene was specifically pH- and temperature-dependent, with the optimal pH and temperature being 8.0 and 40 °C, respectively. The redox mediators 1-hydroxybenzotriazole and veratryl alcohol promoted the transformation of anthracene by HRP; 9,10-anthraquinone was the main product detected from the anthracene oxidation system. The results of this study not only provide a better understanding of the oxidation of PAHs by utilizing a plant biocatalyst, but also provide a theoretical basis for establishing the HRP-catalyzed treatment of PAH-contaminated wastewater.     

Microwave process for volatile organic compound abatement

The CHA Corporation has completed the U.S. Air Force Phase II Small Business Innovation Research program to investigate the feasibility of using a novel microwave-based process for the removal and destruction of volatile organic compounds (VOCs) in effluents from noncombustion sources, such as paint booth ventilation streams. Removal of solvents by adsorption, followed by the regeneration of saturated granular activated carbon (GAC) by microwave energy, was achieved in a single fixed-bed reactor. Microwave regeneration of the fixed-bed-saturated carbon restored the original GAC adsorption capacity. After 20 adsorption/regeneration cycles, the adsorption capacity dropped from 13.5 g methyl ethyl ketone (MEK)/100 g GAC to 12.5 g MEK/100 g GAC. During microwave regeneration of the GAC fixed bed, the concentrated desorbed paint solvent was oxidized by passing the solvent mixture through a fixed bed of an oxidation catalyst mixed with silicon carbide in a microwave reactor. A 98% oxidation efficiency was consistently achieved from the oxidation of VOCs in the microwave catalytic reactor.     

Combined effects of DOM and biosurfactant enhanced biodegradation of polycylic armotic hydrocarbons (PAHs) in soil–water systems

This study systematically investigated the interactive effects of dissolved organic matter (DOM) and biosurfactant (rhamnolipid) on the biodegradation of phenanthrene (PHE) and pyrene (PYR) in soil–water systems. The degradations of two polycyclic aromatic hydrocarbons (PAHs) were fitted well with first order kinetic model and the degradation rates were in proportion to the concentration of biosurfactant. In addition, the degradation enhancement of PHE was higher than that of PYR. The addition of soil DOM itself at an environmental level would inhibit the biodegradation of PAHs. However, in the system with co-existence of DOM and biosurfactant, the degradation of PAHs was higher than that in only biosurfactant addition system, which may be attributed to the formation of DOM–biosurfactant complex micelles. Furthermore, under the combined conditions, the degradation of PAH increased with the biosurfactant concentration, and the soil DOM added system showed slightly higher degradation than the compost DOM added system, indicating that the chemical structure and composition of DOM would also affect the bioavailability of PAHs. The study result may broaden knowledge of biosurfactant enhanced bioremediation of PAHs contaminated soil and groundwater.     

Applying the three R’s: Reduce,reuse, and recycle in the chemical industry

Pollution prevention (P2) assessment was conducted by applying the three R’s, reduce, reuse, and recycle, in a chemical industry for the purpose of reducing the amount of wastewater generated, reusing paint wastewater in the manufacture of cement bricks, recycling cooling water, and improving water usage efficiency. The results of this study showed that the annual wastewater flow generated from the paint manufacturing can be reduced from 1,100 m³ to 488.4 m³ (44.4% reduction) when a high-pressure hose is used. Two mixtures were prepared. The first mixture (A) contains cement, coarse aggregate, fine aggregate, Addicrete BVF, and clean water. The second mixture (B) contains the same components used in the first mixture, except that paint wastewater was used instead of the clean water. The prepared samples were tested for water absorption, toxicity, reactivity, compressive strength, ignitability, and corrosion. The tests results indicated that using paint wastewater in the manufacture of the cement bricks improved the mechanical properties of the bricks. The toxicity test results showed that the metals concentration in the bricks did not exceed the U.S. EPA limits. This company achieved the goal of zero liquid discharge (ZLD), especially after recycling 2,800 m³ of cooling water. The total annual saving could reach $42,570 with a payback period of 41 days.

Implications: This research focused on improving the water usage efficiency, reducing the quantity of wastewater generated, and potentially reusing wastewater in the manufacture of cement bricks. Reusing paint wastewater in the manufacture of the bricks prevents the hazardous pollutants in the wastewater (calcium carbonate, styrene acrylic resins, colored pigments, and titanium dioxide) from entering and polluting the surface water and the environment. We think that this paper will help to find the most efficient and cost-effective way to manage paint wastewater and conserve fresh water resources. We also believe that this paper provides a rich agenda for future research in water conservation and industrial wastewater reuse subjects.     

Evaluating exposure of pedestrians to airborne contaminants associated with non-potable water use for pavement cleaning

Climate change and increasing demography press local authorities to look after affordable water resources and replacement of drinking water for city necessities like street and pavement cleaning by more available raw water. Though, the substitution of drinking by non-drinking resources demands the evaluation of sanitary hazards. This article aims therefore to evaluate the contribution of cleaning water to the overall exposure of city dwellers in case of wet pavement cleaning using crossed physical, chemical and biological approaches. The result of tracer experiments with fluorescein show that liquid water content of the cleaning aerosol produced is about 0.24 g m^?3, rending possible a fast estimation of exposure levels. In situ analysis of the aerosol particles indicates a significant increase in particle number concentration and particle diameter, though without change in particle composition. The conventional bacterial analysis using total coliforms as tracer suggests that an important part of the contamination is issued from the pavement. The qPCR results show a more than 20-fold increase of background genome concentration for Escherichia coli and 10-fold increase for Enterococcus but a negligible contribution of the cleaning water. The fluorescence analysis of the cleaning aerosol confirms the above findings identifying pavement surface as the major contributor to aerosol organic load. The physical, chemical and microbiological approaches used make it possible to describe accurately the cleaning bioaerosol and to identify the existence of significantly higher levels of all parameters studied during the wet pavement cleaning. Though, the low level of contamination and the very short time of passage of pedestrian in the zone do not suggest a significant risk for the city dwellers. As the cleaning workers remain much longer in the impacted area, more attention should be paid to their chronic exposure.     

A fingerprint analysis method for characterization of dissolved organic matter in secondary effluents of municipal wastewater treatment plant

Dissolved organic matter (DOM) in wastewater and reclaimed water is related to water quality, safety, and treatability. In this study, DOM was characterized through a fingerprint analysis method for DOM characterization using resin fractionation followed by size exclusion chromatography (SEC). Resin fractionation was used in the first step to divide the DOM in water samples into six resin fractions, namely, hydrophobic acids (HOA), hydrophobic bases (HOB), hydrophobic neutrals (HON), hydrophilic acids (HIA), hydrophilic bases (HIB), and hydrophilic neutrals (HIN). SEC analysis was then performed to separate each resin fraction into several (n) subfractions with different molecular weights (MW). Thus, the total DOM in the water sample was fractionated into 6n subfractions. After quantification of each subfraction by dissolved organic carbon (DOC), a fingerprint graph was constructed to express the distribution of DOM in the subfractions. The fingerprint analysis method was applied to a secondary effluent sample during ozonation. Ozonation (dose of 10 mg L^?1) removed the DOC only by 8 % and reduced UV₂₅₄ of the sample by 36 %. Fingerprint graphs also revealed that the resin fractions changed quite limitedly but transformation of subfractions occurred notably.     

Assessment of heavy metal and organic contaminants levels along the Libyan coast using transplanted mussels (Mytilus galloprovincialis)

Within the framework of the MYTIOR project in 2009, heavy metals and organic compounds contaminations were assessed in transplanted mussels in 16 different stations along the coasts of Libya. These stations were located at miles offshore industrial/urban sources but in open sea providing original results related to the background contamination rather than linked to a specific coastal source of pollutants. Results indicated mercury (Hg, 0.045–0.066 mg/kg dry weight (dw)), lead (Pb, 0.44–0, 71 mg/kg dw) and copper (Cu, 3.56–4.21 mg/kg dw) were in the same range or at lower value than control for all stations. Chromium (Cr) in Meleta (3.08 mg/kg dw) and Bomba (3.80 mg/kg dw) and Cadmium values in all stations (1.21–2.41 mg/kg dw) were above control. Meleta, stations from the gulf of Syrt and the three eastern stations were the most affected stations by nickel (max at 5.83 mg/kg dw in Syrt) when zinc was in the same range (141–197 mg/kg dw) and above the control (92 mg/kg dw) at all stations. Polycyclic aromatic hydrocarbon (PAH) levels were found in the range of 16.8–42.8 mg/kg (dry weight) indicating low levels along the Libyan coast with acenaphthene and benzo (a, b, k) pyrenes detected mainly in western Libya. The study of PAH ratios indicated a mixed petrogenic/pyrolytic origin. The only polychlorinated biphenyls (PCBs) found in Libya were PCB 101 in one location and PCB 153 in Tripoli, Garrapoli, Syrt, Ras Lanuf and Benghazi (1.2–1.9 μg/kg dw). Insecticides were lower than control in all stations except DDT, only detected in Misratah (3.5 μg/kg dw). Overall, the results indicated a low background contamination and a low pollution extent according to the environmental pressure occurring offshore the Libyan coast.     

Non-steady state partitioning of dry cleaning surfactants between tetrachloroethylene (PCE) and water in porous media

Trapped organic solvents, in both the vadose zone and below the water table, are frequent sources of environmental contamination. A common source of organic solvent contamination is spills, leaks, and improper solvent disposal associated with dry cleaning processes. Dry cleaning solvents, such as tetrachloroethylene (PCE), are typically enhanced with the addition of surfactants to improve cleaning performance. The objective of this work was to examine the partitioning behavior of surfactants from PCE in contact with water. The relative rates of surfactants partitioning and PCE dissolution are important for modeling the behavior of waste PCE in the subsurface, in that they influence the interfacial tension of the PCE, and how (or if) interfacial tension changes over time in the subsurface. The work described here uses a flow-through system to examine simultaneous partitioning and PCE dissolution in a porous medium. Results indicate that both nonylphenol ethoxylate nonionic surfactants and a sulfosuccinate anionic surfactant partition out of residual PCE much more rapidly than the PCE dissolves, suggesting that in many cases interfacial tension changes caused by partitioning may influence infiltration and distribution of PCE in the subsurface. Non-steady-state partitioning is found to be well-described by a linear driving force model incorporating measured surfactant partition coefficients.     

Occurrence of 1,1′-dimethyl-4,4′-bipyridinium (Paraquat) in irrigated soil of the Lake Chad Basin,Niger

Increased use of agrochemical products to improve yields for irrigated crops in sub-Saharan Africa has been accompanied by a significant increase in the risk of environmental contamination. Detailed examples of the fate of pesticides after initial spreading on crop fields are scarce in tropical regions, where safe practices and related health risks are poorly understood by smallholder farmers. In the semi-arid environment of the Lake Chad Basin, SE Niger, both intrinsic properties of pesticides and extrinsic factors such as soil and climate helped to characterize processes leading to an accumulation of pesticides in soils. Analysis by HPLC-UV of a 6 m deep soil profile showed the presence of Paraquat at concentrations from 953?±?102 μg kg^?1 to 3083?±?175 μg kg^?1 at depths between 0.80 and 2.75 m below the land surface. Soil analysis revealed that up to approximately 15 % of the total soil matrix consists of smectites, a clay mineral capable of retaining cationic pesticides such as Paraquat, and a very low content of organic matter (<0.15 wt.% TOC). Paraquat could be stored and not bioavailable in a clayey barrier at approximately 2-m depth and therefore does not represent an immediate risk for populations or environment in this form. However, if the Paraquat application rate remains constant, the clayey barrier could reach a saturation limit within 150–200 years and 180–220 years if we consider a DT50 in soil of ~1,000 days (FAO). Consequently, it could lead to a deeper infiltration and so a pollution of groundwater. Such a scenario can represent a health risk for drinking water and for the Lake Chad, which is a major resource for this densely populated region of semi-arid Africa. Further analyses should focus on deeper layers and groundwater Paraquat contents to validate or invalidate the hypothesis of storage in this clay-rich layer.     

Fluoride removal from aqueous solution by direct contact membrane distillation: theoretical and experimental studies

Direct contact membrane distillation (DCMD) process using polyvinylidene fluoride (PVDF) membrane was used for fluoride removal from aqueous solution. This study has been carried out on heat and mass transfer analyses in DCMD. The dusty-gas model was used to analyze the mass transfer mechanism and to calculate the permeate flux. The heat transfer is analyzed based on energy balance, and the different layers are considered as a series of thermal resistances. Mass transfer analysis showed that the transition Knudsen-molecular diffusion is the dominant mechanism to describe the transport of water vapor through the pores of the PVDF membrane. The most significant operating parameter is the feed temperature. The permeate increases sensitively with feed temperature and velocity, and it shows insignificant change with feed salts concentration. Heat transfer analysis showed the conduction through the matrix of the membrane presents the major part of available energy. The increasing feed temperature leads to increase thermal efficiency (TE) and decrease temperature polarization coefficient (TPC). The experimental results are in good agreement with theoretical values. Therefore, it is suggested to work at high feed temperature, which will benefit both the thermal efficiency and permeate flux. The experimental results proved that DCMD process is able to produce almost fluoride-free water suitable for many beneficial uses.     

A History of Dry Cleaners and Sources of Solvent Releases from Dry Cleaning Equipment

Approximately 25, 000–35, 000 dry cleaning facilities currently operate in the U.S. The release of perchloroethylene and other solvents from these establishments represents a major source of soil and groundwater contamination. The manner in which dry cleaning solvents escape from dry cleaning plants is, for all practical purposes, identical for chlorinated and petroleum hydrocarbon solvents and is related to one of the following events: the catastrophic failure of a component of the dry cleaning system, the improper installation, operation or maintenance of the dry cleaning equipment or a combination of all of these causes. Acceptable customs, codes and regulations can also dictate what is authorized for operation of a dry cleaning facility in a particular community, geographic area during a particular time frame. Environmental litigation dealing with the origin of a solvent release from dry cleaners tends to focus on the design and manufacture of dry cleaning industry machines such as washers, washer extractors, tumblers, solvent filters, water separators, stills and spotting boards. A thorough analysis of the daily operations of dry cleaners often reveals that poor maintenance, failure to follow the manufacturer's instructions and the actions of the operator are the most likely causes of soil and groundwater pollution. In order to forensically evaluate the most probable origins of a solvent release and to examine issues regarding liability, a thorough understanding of the history of dry cleaning and a detailed analysis of the operation and maintenance of the dry cleaning equipment are necessary. The discovery of solvent plumes in the vicinity of dry cleaning plants may suggest that the solvent source is the dry cleaning plant; however, the presence of these plumes does not necessarily indicate that the dry cleaning equipment was defectively designed or manufactured. A thorough review of the type of equipment used over the life of the dry cleaning plant and verifiable solvent mileage records frequently indicates that operators of the plant have disposed of solvent and contaminated solids into the municipal sewer or on ground surfaces.