Environmental Impacts of Car Washing SummaryCar wash chemicals – substitution of A- and B-substancesTest of wastewater treatment plants for car wash facilities. Wastewater Study of Manual Washing In 1999-2000 the project partners prepared the project: ”Car Washing –Status and Strategies”2 (below called: Phase I-project). The project describes the environmental impact from car wash facilities and proposes strategies for municipal wastewater regulation and strategies for reducing the environmental impacts of wastewater through cleaner technology. This project was launched to follow up the above project in a developmentoriented Phase II, focusing on the specific strategies for reduction of the environmental impacts of wastewater from car wash facilities. The project was divided into three main activities:
Car wash chemicals – substitution of A- and B-substancesThe environmental assessment of car wash chemicals in Phase I included products which covered about 95% of the consumption in car wash facilities in Denmark. In Phase II the number of participating chemical suppliers is increased from two to four suppliers. The project does not include a new study of the quantities of car wash chemicals sold in Denmark. But on the basis of the studies from the Phase I project it is estimated that the products examined represent more than 95% of the quantities sold. The substances of the car wash chemicals were grouped according to their environmental impact in categories A, B, and n.a. (not assessed substances). A-substances are undesirable in wastewater since the substances are not easily degradable, are very toxic for aquatic organisms and/or may cause irreversible health effects on human beings. The B-substances should be limited in order not to exceed the environmental quality requirements, as B-substances are not easily degradable and are toxic for aquatic organisms. C-substances are normally unproblematic substances while n.a. are substances that cannot be assessed due to lack of data. For precautionary reasons n.a.-substances should be considered as potential A- or B-substances. The environmental assessment of the Phase I project showed that the main sources of the discharge of the environmentally critical A- or B-substances are wax products, foam products, insecticides and rim cleaners as well as cleaning products for car wash facilities. Especially wax products display critical environmental profiles as it was not possible to choose wax products without A- or B-substances at the present time. On this basis the aim of the Phase II project was to:
During one year a substitution process was carried out in which the supplied products – and proposals for new substances – were assessed. During this substitution process a total of 17 A- and B-substances were removed from the products. The types of substances were cationic surfactants, oil distillate, alkyl sulphonate, siloxanes and EDTA. A total of 21 new products were developed, of which 19 were commercially available. All A-substances in the wax products had been removed. By the end of the project 10 new wax products without A-, B- and n.a.-substances had been developed. Two suppliers have launched entire series of products for car wash without environmentally critical substances (A- and B-substances) which will now be marketed in Denmark. One of the series was tested in four car wash facilities during the project process. None of the service stations recorded any complaints from customers of bad washing during the tests. The second series was tested by the end of the project. The Danish Environmental Protection Agency plans to present the future substitution of A- and B-substances in new products on a homepage on: www.mst.dk . This site will show current ABC-assessments of the car wash chemicals. Test of wastewater treatment plants for car wash facilities.The Phase I project included a number of proposals for reducing the content of environmentally critical substances in wastewater from car wash facilities. One proposal for strategies was the use of wastewater treatment plants using recycled wash water in each individual car wash facility. So far only few wastewater treatment plants have been installed in car wash facilities. This is due to the fact, first, that customers have limited faith in the reliability of the plants and, second, that the lack of documentation for the ability of the wastewater plants to limit the discharge of the environmentally critical substances. On this basis the purpose was to:
This assessment is meant to supply customers and authorities with means of assessing the various types of wastewater treatment plants for car wash facilities. The studies comprised four wastewater treatment plants which were implemented in four car wash facilities in service stations: three biological wastewater treatment plants and one chemicalphysical plant. The plants were selected by the task group of the project among commercially available wastewater treatment plants for car wash facilities known in the oil trade. Before the start of the Phase II project it was possible for car wash facilities to obtain “the Nordic Swan”, an environmental label. The label can only be awarded to facilities that have established a wastewater treatment plant at the car wash facility. The study of the Phase II project was carried out in such a way that it can be used as part of the documentation which must accompany the application for the environmental label. The basis of the study is an existing car wash facility, as shown in figure 1. Figure 2 outlines a typical car wash facility with a wastewater treatment plant. Average values for the amounts of water from the test of treatment plants are stated. Figure 1 Water streams for a traditional car wash facility, with brush washing and use of recycled water for undercarriage washing. Average values according to monitoring in wash facilities without wastewater treatment plant are stated. Figure 2 Water streams for car wash facility with wastewater treatment plant. Average values from project test of wastewater treatment plant are stated. Figure 2 shows that after establishment of a wastewater treatment plant of the type tested in the project, recycled water is used for both carriage and undercarriage washing, whereas only freshwater is added for the last rinsing. The aim of a treatment plant in the car washer is usually a reduction of the environmentally critical wastewater parameters in the wastewater that is discharged to a sewer. Furthermore, water reductions can be obtained by using the treated recycled water. After establishment of treatment plants the discharge of wastewater will typically be reduced by about 94% or more. The above example shows a wastewater reduction from 136 l/car to 8 l/car. The water used for ion exchange and desalination of the freshwater for the last rinsing (about 13 l/car) is not included. Ion exchanger and reverse osmosis plants have been established in about 50% of the Danish car wash facilities. Water consumption, reliability and result Three of the wastewater treatment plants were tested during the period from March to December 2002, and the fourth plant was tested from August 2002 to January 2003. During the test period detailed supervision took place, and in April, August and December the treated water was monitored prior to being discharged to the sewer. The supervision showed that within the test period it was possible to meet the requirement of the ecolabel “Nordic Swan” of a maximum freshwater consumption of 70 l/wash. Figure 2 shows an average water consumption of 35 or 22 l/car during the test period (before and after ion exchanger and reversed osmosis). During the test period no stoppages were recorded in the four car wash facilities which can be attributed to the running of the wastewater treatment plants. No complaints from customers were received. No obnoxious smells or complaints of problems with drying or with stains were observed. The staff was interviewed by DHI/IPU after the test period. Before the start of the project one of the barriers to the use of wastewater treatment plants was dosing of precipitation chemicals used in treatment plants earlier on. None of the plants tested in the project use chemical s in the treatment processes. Another expected barrier was whether the wastewater treatment plants would be able to handle wax polish, which today is included in the series of chemicals used in many car wash facilities. Two of the participating wastewater treatment plants were tested in car wash facilities with wax polish, and it turned out that it was no barrier to the running. Removal of environmentally critical substances The monitoring in Phase I of the project in traditional car wash facilities shows periodic exceeding of the limit values stipulated by the Danish Environmental Protection Agency for cadmium, lead, zinc, DEHP and mineral oil. Monitoring of the wastewater from the car wash facilities with treatment plants showed that it is possible to comply with the target values of Phase I of the project. The target values are based on the limit values of the Danish Environmental Protection Agency and express the impact per car and correspond to compliance with the limit values at a wastewater discharge of 150 l/car (equivalent to the typical water consumption in brush washing). The target values are the result of the following multiplication of the limit values of the Danish Environmental Protection Agency by 150 l/car (e.g. cadmium: 3 µg/l x 150 l/car = 0.45 mg/car). Likewise, it was possible to comply with the limit values of the Nordic Swan. The discharge of heavy metals, DEHP and mineral oil substances per car was reduced by a factor 10 to 1000 in comparison to wastewater from traditional car wash facilities without wastewater treatment plants. Heavy metals and organic compounds, which are not degradable during the biological processes of the plants are accumulated in the sludge of the plants. The sludge is being removed – as sludge from ordinary sand traps in car wash facilities – as hazardous waste. Moreover, the studies on hygiene showed that it is possible to comply with the E. coli requirements of the Nordic Swan. A single incident where the E. coli requirement had been exceeded was observed in the car washer in Frederikssund. It was possible to explain this incident; a sludge exhauster had polluted the water with E. coli during sludge removal and refilling in the plant. In future, water from emptying the sand trap should not be returned from the sludge exhauster to the sand trap when wastewater treatment plants with recycled washing water have been established. There is every possibility that sludge exhauster will be polluted with E. coli from previously visited plants. Only one monitoring operation showed Legionella, namely the plant in Lyngby where a low level was observed (below the limit of reaction for hot-water systems. This observation will probably stem from the hot-water added to the water system of the car washer. The plant in Lyngby was the only plant with a periodic supply of hot-water to the system. The supply of hot-water was stopped. Financial assessment Examinations of the financial situation of the wastewater treatment plants show that it will be possible to run a treatment plant in a car wash facility with 10,000 to 15,000 car washes every year. The plant will reach a balance around this number, and larger numbers will give savings. However, zero point will to a large extent depend on the price of water and on the consumption of water in the car wash facility. It is therefore always necessary to carry out a specific financial estimation taking the actual car wash facility into consideration when establishing a car washer. As mentioned above the Danish Environmental Protection Agency plans to set up a homepage as a follow-up of this project (via www.mst.dk ). This site will show a spreadsheet to help future buyers of car washers get a good overview of the financial aspects regarding their specific purchase. Wastewater Study of Manual WashingMoreover, the aim of the project was to study the environmental impacts of manual washing of private cars. This study was made to follow up the estimates of the impact from manual washing which were proposed in the Phase I project. The study should be considered a preliminary statement of the impact from simple and well-described manual washing. Manual washing can take place in many ways, and different methods use much water and many chemicals, or only little water and few chemicals. The monitoring of wastewater carried out in the study covers only one single washing process. The purpose of the project was:
The total amount of automatic car washes is estimated at 13.4 million washing operations a year, equal to 65% of all washes. Thus, 35% of all car washes are manual, equal to 7.2 million a year. Accordingly, the average number of car washes can be estimated at 11 per car (automatic + manual car wash). The consumption of water in the examined manual car wash amounts to approximately 100 l at normal water pressure and approximately 75 l at high pressure washing. In total the water consumption in manual washing is estimated at 790,000 to 1,500,000 m3/year. These figures include an amount of untreated wastewater discharged to the water body estimated at 590,000 to 880,000 m3/year. Manual washing was carried out by means of ordinary water pressure and high pressure. In addition to this, the wastewater was characterised both in a summer situation and in a winter situation. A comparison between washing at ordinary water pressure (summer) and washing at high pressure (summer) showed increased concentrations for all parameters in the wastewater from the washing at high pressure. A comparison of the amounts per car showed less obvious differences, and for the parameters Total-N, Total-P and LAS no differences were seen. In winter the wastewater impact apparently depended more on how dirty the car was than on how the car was washed (ordinary pressure or high pressure). The study showed that washing at high pressure in winter did not result in a heavier pollution load per car than washing at ordinary water pressure. When the concentration of wastewater components in the wastewater from manual washing was compared with the limit values of the Danish Environmental Protection Agency for discharges to the sewerage system, increased concentrations of DEHP, LAS, suspended matter, lead, cadmium, chrome, copper and zinc were observed. On this basis it cannot be recommended to discharge wastewater from manual washing directly to the soil, to water bodies or rainwater systems in separate sewers. Instead the wastewater should be discharged to sewerage systems connected to a wastewater treatment plant. 2 Car washing facilities – Status and strategies. Environmental project from the Danish Environmental Protection Agency No. 537, 2000.
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