Bilvaskehaller

Summary

Background

Several Danish and foreign studies have indicated that car washing facilities contribute to environmental impacts by wastewater containing heavy metals, organic xenobiotics and mineral oil. At the same time, many municipalities are now facing a demand for elaborating wastewater permits to the car washing facilities.

Purpose

The purpose of this project has been to study the environmental impacts of and the use of technology by Danish car washing facilities and, based on this, to propose strategies for reducing the environmental impacts as well as strategies for a municipal wastewater regulation.

Car wash in Denmark

Today there are about 1,320 car washing facilities in Denmark. The project includes the approximately 1,050 car washing facilities which are situated at the service stations of the oil companies. A total of approximately 11.5 million cars are washed every year in Danish car washing facilities. About 95% of all washing in car washing facilities is brush washing. The rest is brushfree washing or tunnel washing.

Manual washing

Approximately the same number of car washes – about 11.5 million – are carried out outside the car washers based on the assumption that around 50% of the car washing in Denmark is manual washing. The wastewater resulting from approximately 2/3 of the manual washing will either percolate into the soil or be led directly to a water body without any treatment provided that 50% is carried out outside sewered areas and that 50% of the sewered areas are sewered separately. Manual washing – including private use of car wash chemicals – is not studied in details in this project but it is estimated that the discharge from private washing is at least as important as the discharge resulting from the car washing facilities.

Focus on the environmental impact of wastewater
The environmental impact of car washing facilities is dominated by the content of a number of substances in the wastewater. These substances will be concentrated in sand traps, oil traps as well as in internal wastewater treatment plants, if any. Due to this fact, the waste parameters are not studied separately in the project since the environmentally critical parameters will be the same as in the wastewater. The waste must be removed as harmful waste because of the content of mineral oil. It is estimated that the energy consumption, which corresponds to 0.65 – 1 kWh per wash, is of practically no importance compared to the total energy consumption of the society. Based on this, focus of the project has been put on the environmental impact of the wastewater.

Sources

The sources of the substances contained in the wastewater from the car washing facilities can be divided into the following main groups:

• Car wash chemicals (for car washing as well as for cleaning of the facility)
• Cars (smudging/corrosion from components and dirt originating from atmospheric fallout and road surface)
• Car washing facilities (smudging/corrosion from installations and buildings)

In order to study the importance of the environmental impact of the wastewater an environmental assessments of the applied car wash chemicals have been carried out during the project as well as a wastewater measuring programme at three selected car washing facilities.

Environmental assessment of car wash chemicals
The environmental assessment of car wash chemicals included about 95% of the total consumption by car washing facilities in Denmark. The substances of the car wash chemicals were grouped according to their environmental disruption in category A, B, C 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 incurable 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.-substances are substances which cannot be assessed due to lack of data. Out of prudence, n.a.-substances should be considered as potential A- or B-substances.

The environmental assessment showed that according to a conservative estimation a total of 28 tonnes of A-substances, 39 tonnes of B-substances, 220 tonnes of C-substances and 63 tonnes of n.a.-substances is being discharged every year from Danish car washing facilities. The conservative estimation is based on the maximum amounts of the substances in question according to the concentration intervals stated for the products by the chemical suppliers.

Types of products and substances

The main sources of discharge of A- and B-substances are wax products, foam products, insecticide and rim cleaners as well as cleaning products for car washing facilities. The types of substance are mainly cationic and nonionic surfactants and complexing binders.

Pilot monitoring programme

The monitoring programme of the project was carried out as a pilot monitoring programme at three car washing facilities. The pilot monitoring programme included a very broad spectrum of analytical parameters in order to ensure a detailed study of the critical pollution parameters of the wastewater and the waste from car washing facilities. The monitoring programme was carried out at the beginning of March 1999 where monitoring were accomplished during 8 days at each of the three car washing facilities. During the monitoring period two of the car washing facilities had their normal monthly cleaning of the facility. In order to document whether the results obtained from the pilot monitoring programme are general for car washing facilities in Denmark, it is necessary to carry out monitoring at a larger number of car washing facilities. A subsequent monitoring programme can be limited to the established critical analytical parameters.

Heavy metals and mineral oil

The pilot monitoring programme indicated periodic exceedings of the limit values stipulated by the Danish Environmental Protection Agency for the heavy metals lead, zinc and cadmium as well as for mineral oil. The average values for all heavy metals were below the limit values. One out of three car washing facilities did not exceed the limit value for mineral oil in average. The exceeding for lead, zinc and mineral oil were to a certain degree connected to the days where cleaning of the facility took place – however, this connection was not unambiguous.

DEHP

The average of DEHP, (di-(2ethylhexyl)phthalate) turned out to be above the provisional calculated limit value. The Danish Environmental Protection Agency has not yet established a limit value for DEHP. DEHP is estimated to primarily originate from washout from PVC-underselling of new cars. Washout of DEHP from PVC increases at high temperatures and based on this a larger washout of DEHP must be expected during the summer half-year.

COD/BOD

The average COD/BOD-scale was measured to above three. A COD/BOD-scale above three indicates that there are slowly degradable substances in the wastewater. This is estimated to primarily originate from slowly degradable components of the applied car wash chemicals.

Share of inlet to Danish WWTPs

If the results of the pilot measuring programmes are supposed to be representative for Danish car washing facilities and if the loads are supposed to be situated between the measured minimum and maximum values, the total load originating from Danish car washing facilities can be compared to the total yearly inlet to WWTPs in Denmark.

If only the amount of wastewater is considered, the car washing facilities account for between 0.2 and 0.4% of the inlet to Danish WWTPs. As for heavy metals and DEHP the share of the car washing facilities represents as follows (days of cleaning are not included):

Strategies for wastewater regulation and cleaner technology

Based on the environmental impact assessment of car wash chemicals and the results of the pilot measuring programme the project, makes proposals for a strategy concerning the municipal wastewater regulation and possible reduction strategies in form of cleaner technology in the car washing facilities.

Objectives for wastewater regulation

The main objective of the proposal for wastewater regulation is a stable compliance with the guideline requirements of the Danish Environmental Protection Agency. The objective specifies concrete targets for emission parameters and car wash chemicals respectively.

Target values for emission parameters

The wastewater regulation is proposed to be accomplished by means of emission parameters expressed as target values. The target values are fixed on the assumption that 150 l wastewater are discharged for each conventional car wash without recirculation multiplied by the guideline concentration limit values of the Danish Environmental Protection Agency. The acceptable amount of discharged pollution is consequently defined from the assumption that the typical/conventional amount of discharged pollution originating from this trade should be able to comply with the guideline concentration limit values – expressed by the unit mg per washed car. By using the amount of pollution per washed car the amount of wastewater can be reduced without exceeding the permissible amount of pollution per washed car.

Target for car wash chemicals

The target for car wash chemicals is first of all that all A-substances should be replaced and – from a principle of precautionary action – that no products should contain n.a.-substances. Secondly, it is proposed that the B-substances should be substituted from the washing chemicals or that it –is proved through concrete documentation that they are not exceeding the environmental quality requirements.

Technology and product development is necessary to reach targets

Technology and product development is necessary to reach the fixed target values for emission parameters in wastewater as well as the targets laid down for car wash chemicals. The achievement of target values for emissions parameters will need reductions of 15-90% for the individual parameters compared to the actual discharged. In order to achieve such reductions it will be necessary to change the washing and/or the water treatment processes.

Achievement of the targets for car wash chemicals will need product development. A few number of products within the range of car shampoo, foam products and products for cleaning of car washing facilities are already now free of A-, B- and n.a. substances, see chapter 2. But as for the other types of products there is a need for product development in order to make products which do not contain the environmentally problematic substances.

Temporary requirements in waste water permits

Based on this, the deadline for achievement of the targets should be compared to the development of technologies and products. It is therefore proposed that the municipalities start by fixing temporary requirements in their wastewater permit and then – after a period where the possibilities for development of technologies and products are documented – tighten up the requirement values for the established targets.

Proposals for reduction strategies

The project makes proposals for reduction strategies in relation to each individual pollution parameter. The principle is that the reduction should take place directly at the source wherever it is possible. This means that possible reduction potentials through changes in the use of washing chemicals, changes of the washing process and changes in the construction of car washing facilities should be examined together with possible recirculation technologies.

Recirculation technologies

There is a large number of commercially available recirculation systems at the market but only few types have been installed at relatively few car washing facilities. The installations are primarily based on chemical precipitation and flotation. However, there is a general misthrust in the trade of the operational steadiness of the existing recirculation systems. Whether the available systems are actually able to reduce the outlet of the environmentally problematic groups of substances has not been examined during this project.

Technologies such as adsorption on active coal or biofiltration and membrane filtration or evaporation all have the potential of separating the environmentally problematic groups of substances. Several of the available systems have a treatment level which includes active coal. Recirculation systems based on biofilters are developing fast. It would be advantageous for the trade to involve these two technologies together with the membrane filtration and the evaporation in the current developing work within recirculation systems for car washing facilities.

Due to the present prices of water the recirculation systems have generally too long pay back periods (7-10 years) and based on this they represent a limited financial potential. But since it is hardly realistic to reduce all pollution parameters at their sources, wastewater treatment might turn out to be indispensable.

Reduction strategies

According to chapter 6, proposals for reduction strategies may be summarised as follows:

• Substitution of A-substances and collection of data for n.a.-substances followed by substitution of or documentation for B-substances and examination of the influence of such substitutions on the COD/BOD relationship
• Environmental assessment of the most common car wash chemicals for private use
• Examination of the impact of different types of undercarriage washing on the content of DEHP in wastewater
• Examination of the possibilities for carwash programmes without the final use of dry helping chemicals and airdrying as well as a minor market surveys
• Examination of the impact of the choice of materials and construction of the car washing facilities on the content of heavy metals in wastewater
• Examination of the capability of selected recirculation technologies to remove the environmentally critical parameters from the wastewater

It is proposed to examine the reduction strategies in a subsequent project in order to study the impact of each individual proposal for strategies on the wastewater quality.

Final evaluation

It is proposed that the reduction strategies are followed by a final evaluation, which is supposed to result in recommendations for reducing the environmentally critical wastewater parameters in the most advantageous way seen from a technical, a financial as well as an environmental point of view.