Clean vehicles, polluted waters: empirical estimates of water consumption and pollution loads of the carwash industry
Clean vehicles, polluted waters: empirical estimates of water consumption and pollution loads of the carwash industry
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Date
2018
Authors
Monney, Isaac
Donko, Emmanuel Amponsah
Buamah, Richard
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Abstract
Carwash stations use large volumes of water and release harmful chemicals into the environment through their
operations. While a significant body of literature has focused on exploring water use in the carwash industry, none
has provided comprehensive information on both the pollution loads of the wastewater emanating from this
industry and water consumption. Understanding how much water is used and the pollution loads of wastewater
from this industry is useful to ensure adoption of water conservation measures and design wastewater recycling
systems given the dwindling freshwater resources globally. This study estimated the freshwater quantities used to
wash different vehicle types and the pollution loads of the resulting wastewater in the Kumasi Metropolis. Seven
proxy carwash stations were purposively selected and monitored to estimate the water used to wash six different
categories of vehicles. Composite wastewater samples from three carwash stations were analysed for concen trations of different contaminants which were used to compute pollution loads. Using R software, one-way
ANOVA with Tukey's (HSD) post-hoc testing and 2-sample t-test at 95% confidence interval were employed to
test statistical differences. After an 8-week monitoring campaign involving 3,667 vehicles, the study showed that
average water used for each vehicle type were in the order: Motorbike - 97L (95% CI: 90–103L); Salon car - 158L
(95% CI: 154–161L); SUV - 197L (95% CI:191–203L); Buses/Coaches - 370L (95%CI:351–381L); Articulated truck
1,139L (95% CI:916–1,363L); Graders/Loaders - 1405L (95% CI:327–2,483L). Overall, the carwash industry in
the Metropolis uses about 1000m3
of freshwater daily and discharges the resulting wastewater into waterways
untreated. The wastewater has a low Biodegradability Index (0.3–0.4) and is characterized by a mildly alkali pH
(7.6–8.6) with high levels of Sulphates (40.8–69.8 mg/L), COD (990–1413 mg/L), TSS (1260–3417 mg/L) and E.
coli (2.3–4.7 103 CFU/100mL). Pollution loads of BOD and COD were up to 2tons/year and 6tons/year
respectively. Stipulated effluent discharge guideline values were mostly exceeded – in some cases by up to 68
times. To avert the unbridled wastage of freshwater, the study recommends enforcement of wastewater recycling
for all carwash stations and promulgation of a tax system that rewards stations that recycle wastewater and
surchages those wasting freshwater.
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Monney, I., Donkor, E. A., & Buamah, R. (2020). Clean vehicles, polluted waters: Empirical estimates of water consumption and pollution loads of the carwash industry. Heliyon, 6(5).