Hydrocarbon-based cleaning solvents in a car wash
Cars quickly become dirty in the Nordic climate, so effective washing processes and cleaning agents are needed to clean them. Most car washing is performed mechanically in a car wash facility, but also various methods of manual washing are common.
Hydrocarbon-based cleaning solvents are used a lot in car wash facilities because they dissolve dirt well. Hydrocarbon solvents are particularly well suited for removing the greasy dirt formed by accumulations of bitumen, traces of fuel, oil and de-icing salt on the surface of the car.
Hydrocarbon solvents are classified as substances that are hazardous to health, and often also as substances causing chronic health effects. Furthermore, as flammable substances, they can pose fire and explosion risks while also presenting a serious threat of contaminating soil and groundwater.
Composition of most commonly used hydrocarbon solvents in a car wash
Cleaning solvents typically comprise aliphatic, naphthenic and aromatic hydrocarbons. Of these, aromatic hydrocarbons are particularly effective solvents, but they also pose greater risks to health.
Washing processes and routes of exposure
Cleaning solvent is typically spread onto the surface of the car to be washed as a roughly 5…30% microemulsion. The microemulsion is spread as a fine spray that is allowed to act on the surface for some tens of seconds. After this, brushing and rinsing remove the solvent and dissolved dirt along with the water, which takes it into the ground or into a wastewater collection system.
During the spreading phase, high local concentrations of solvent spray and aerosols can occur. For this reason, particular attention must be given to the ventilation in the washing area when using hydrocarbon solvents. If working without personal protective equipment, an employee might inhale any solvent vapours and aerosols in the air, and these can cause serious damage to the health.
Health hazards and environmental hazards
Hydrocarbon solvents are chemicals that pose risks to health and to the environment. Diseases known to be linked to solvents include various types of damage to the central nervous system. These diseases exhibit symptoms such as unusual fatigue, memory and concentration disorders, headache, psychological aberrations, symptoms deriving from the peripheral nervous system, and dizziness. Also, some hydrocarbons are known to be carcinogenic. Particularly benzene, which occurs in hydrocarbon solvents in at least small quantities, is known to cause cancer. Consequently, respirators should always be used when working with hydrocarbons, and also migration of vapours to other work spaces (eg, via ventilation ducts) should be prevented. For these reasons, efforts are being made to replace hydrocarbons with safer, renewable solvents.
Car washing activities account for most of the wastewater produced by carwash and fuel distribution facilities. The chemicals used in car washing, if released into the environment, are detrimental to the soil and groundwater. Furthermore, in high concentrations they can also cause harm in the sewer network and in wastewater cleaning processes.
Typically, some 2000-2500 litres of water per hour are used in a car wash. Water containing detrimental concentrations of oils and greases is prevented from being conducted into the public wastewater network by a correctly dimensioned Class II oil separator. Proper operation of the separator should be checked and the separated mixture of waste oil and solvent removed often and delivered in the correct manner for treatment as hazardous waste. There should also be a sampling and shut-off trap at the wash site, situated upstream from where wastewater is conducted into the public wastewater network. A facility must always agree with the sewage utility operator about the arrangements for industrial wastewater.
Work safety and the storage and handling of hazardous chemicals
An operator of a facility is always responsible for the safety of his/her employees. Hydrocarbon solvents are classified as substances that are hazardous to health, and often also as substances causing chronic health effects. For this reason, employees should be given adequate induction training and instructions on the use of the wash chemicals being used, health inspections should be arranged, Safety Data Sheets should be on display and readily available, employees should be provided with the necessary personal protective equipment, and the use of such equipment supervised.
Hydrocarbon solvents are generally flammable materials and they can present a risk of fire and explosion. Consequently, the requirement of all legislation relating to chemical safety and explosion proof premises should be addressed. For example, a facility operator using hydrocarbon solvents should assess the explosion risks attached to his/her operations and classify areas exposed to explosion risk (such as solvent dispensing and storage locations, as well as the oil separator and its immediate environs). The operator of a facility must also keep an explosion protection document. The pertinent regulations for the transport of hazardous substances must be addressed when transporting hydrocarbon solvents.
Summary
When using hydrocarbon solvents, particular attention should be given to all aspects relating to the safety of employees and customers. Employees should wear personal protective equipment and washing spaces should be adequately ventilated. The migration of vapour to other work spaces must be prevented.
The use of solvents can pose a risk of fire and explosion, so work procedures and the equipment selected should address this fact.
The use of hydrocarbon solvents requires appropriate technical solutions for the pre-treatment of the wastewater produced in washing, as well as the correct use and supervision of these solutions.
Sources:
Ajoneuvojen pesutoiminta huoltoasemilla ja muissa vastaavissa kohteissa (in Finnish), [Vehicle washing in service stations and other similar facilities], Finnish Petroleum and Biofuels Association, 2015.