Abstract
Carwash wastewater (CWW) can be a significant source of environmental pollution due to the diversity and high concentrations of contaminants it contains. This toxic wastewater can contain several different heavy metals that if left untreated, can enter surface and sub-surface waters. Innovative, nature-based solutions such as low-impact development (LID) technologies may provide an eco-friendly CWW treatment process that is both effective and affordable. This research reviews the available literature to provide definitive values of flowrate and contaminant concentrations found in CWW around the globe. Dividing LID technologies into two groups, vegetated and unvegetated systems, the authors explored the literature for the general performance of these technologies to sustainably treat heavy metals in CWW. Depending on the car wash’s size and intended purpose, whether cleaning vehicles in agriculture-based rural communities, mining, or in high-density urban environments, volumetric flowrates requiring treatment found in six different countries ranged from 35–400 L/car. CWW also contains a wide range of contaminants at various levels, including COD, turbidity, TDS and TSS, surfactants, oils and greases, and heavy metals such as lead, cadmium, zinc, copper, chromium, and iron. Heavy metal removal by both vegetated and unvegetated LIDs shows mixed results in the literature, but given the different processes involved in both types, the authors propose a system that combines these types in order to provide all the necessary removal processes, including mechanical filtration, adsorption, sedimentation, chemical and biological treatment processes.
Highlights
Vehicles are not generally given consideration when addressing a region’s wastewater generation
Wastewater from vehicle-washing facilities offer a wide range of contaminants including heavy metals; sand and dust; detergents; surfactants; phosphates; grease; waxes; hydrofluoric acid; petroleum hydrocarbon wastes such as motor oil, diesel and petrol [4,5,6,7]; and unacceptable levels of acidity and turbidity [9]
This paper reviewed the literature pertaining to carwash wastewater characteristics and assessed the potential for low-impact development technologies to remediate heavy metal contamination in carwash wastewater, with the intention of making the practice more sustainable and potentially providing a water resource
Summary
Vehicles are not generally given consideration when addressing a region’s wastewater generation. LIDs are technologies that provide effective solutions for sustainable stormwater management and treatment because they treat the contaminated water at the source, use native materials, work by gravity drainage with no energy input, uses nature-based solutions for remediation, and recreate the landscape’s original permeability prior to urbanization [20]. This paper has two objectives: (1) to assess the literature for definitive quantities of possible CWW daily flowrate generation volumes, contaminants present, and concentrations observed in carwash facilities around the world in both urban and rural communities, and (2) to assess the potential for LID technologies to provide sustainable treatment of heavy metals in CWW in rural, remote, and impoverished regions. Very little work has been done in this area, and many of the sources were difficult to access, the synopsis that follows is a synthesized summary of what is accessible to the public in the technical and non-technical literature
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