Hybrid-process including electrocoagulation for the real carwash wastewater treatment using a new continuous undivided tubular reactor

A coagulation-based continuous tubular electrochemical reactor has been designed to treat real carwash wastewater in a flow rate of 100 mL/min. This reactor made of an ordinary iron tube cathode with a commercial aluminum rod anode at the center. Equipment and chemicals needed for this method can be easily and cheaply obtained through non-scientific commercial sources. The one-factor at a time approach was used to investigate the effects of operating variables. Current density, flow rate, electrolysis time and electrode material were selected as independent variables while COD removal was considered as the response function. The experimental results showed that the proposed method can remove 89% of COD from 10 liters of carwash wastewater in a "single-pass" and more than 99% in a "double-pass" through the flow reactor. This reactor has short treatment time, low energy consumption, favorable mass transfer and low ohmic drop and does not need to adjust the pH or add electrolyte additionally to save costs. Also, this approach is resistant to undesirable phenomena such as passivation of the electrode surface, cell polarization, electrode surface fouling and reduction of electrical conductivity that may occur during electrolysis. The treated wastewater can be reused in the carwash industry as well as for irrigated agriculture.