Exploring the Potential in LID Technologies for Remediating Heavy Metals in Carwash Wastewater

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.

Heavy metal contamination from fuel station run-off and carwash wastewater: An assessment of ecological risk and experimental treatment

“…Due to the potential for synergistic effects of heavy metals in the environment [ 49 ], relying solely on single element indices can be inadequate for assessing contamination and associated risks. Therefore, the environmental indicators used to evaluate the risk of pollution from CW wastewater and FS run-off to the environment included single-element risk indicators such as the contamination factors and multi-element indices such as the modified degree of contamination (mCD) and the potential ecological risk index (PERI) to quantify the overall synergistic ecological risk [ 50 ].…”

“…Fuel station run-off (FSR) may gather petroleum hydrocarbons and heavy metals such as lead and nickel from leaded fuels (gasoline) spills [ 15 ], zinc and cadmium from the vehicle tires and galvanized parts, other chemicals in lubricant oil and grease [ 16 ], as well as suspended particulates, and deposit them into water bodies in the environment [ 17 ]. Carwash wastewater (CWW) may also contain a variety of chemical substances emanating from washing chemicals and detergents, worn brake discs and pads, mud from untarred roads and dirt from transported passengers and cargo, which may contribute to the chemical oxygen demand, turbidity, total dissolved solids, and total suspended solids, surfactants, oils and greases, and heavy metals [ 18 ] in the wastewater.…”