ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Electrochemical coagulation of car service station wastewater: multi-parameter removal, sludge aspects and operating costs

Mahesh Sahana, Benamanahalli Motaiah Krishna, Shivaswamy Mahesh, and Suresh Lad Chidanand

Department of Environmental Engineering, Sri Jayachamarajendra College of Engineering, Constituent College of JSS Science and Technology University (Formerly SJCE), Mysuru, India

E-mail: sahanam@sjce.ac.in

Received: 4 May 2025  Accepted: 9 March 2026

Abstract:

Electrochemical coagulation (ECC) of Car Service Station Raw Wastewater (CSSRWW) was investigated in a batch reactor using Stainless Steel (SS-304) metal electrodes. Current densities (CD) of 2.5–12.5A/m² were applied in discrete ECC experiments, of which 7.5A/m² CD with four plate bipolar arrangement, was found optimal achieving maximum multi-parameter(s) removal in ≤ 60 min electrolysis time (ET). For 7.5A/m² CD, COD, BOD₅, Color, O&G, chloride, turbidity and TDS removals were 87.5%, 73.3%, 88.6%, 94.1%, 67.1%, 93% and 80% respectively in the post ECC supernatant. ‘Mass balance’ was established between solids, electrode dissolution and dry ECC sludge (DES). For an optimal CD of 7.5A/m², ED and DES were 617 mg/L and 370.4 mg/L. The post ECC slurry obtained showed excellent settling characteristics for 7.5A/m² CD. Gravity filtration of ECC slurry showed clear supernatant in filtrate for 5 and 7.5A/m² CD, with less moisture in settled sludge. Sludge Volume Index (SVI) for optimal 7.5A/m² CD was 140 mL/g achieved in ≤ 60 min ET. Elemental composition of DES showed 43% O, 20% Fe and 16% C. The XRD of DES showed amorphous nature. For 7.5A/m² CD, power consumption was 2.8 kWh/m³ of CSSRWW treated. Operating costs for 7.5A/m² CD was 53.25 INR/cum of treated CSSRWW. Clear water reclamation by 80% was achieved, along with recovery of iron ingots, and sludge for use as adsorbent. ECC kinetics showed evidence of simultaneous removal of multiple pollutants from CSSRWW obeying Pseudo-first-order reactions giving high k and R² values. The ECC process proved its efficacy and robustness in remediating CSSRWW.

Graphical abstract

Keywords: Car service station raw wastewater; Electrochemical coagulation (ECC); Sludge aspects; Solids mass balance; Operating cost

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-04804-7

Chemical Papers 80 (6) 6863–6887 (2026)