Pretreatment of deproteinised natural rubber wastewater and evaluation of its anaerobic treatment performance

Abstract

Deproteinised natural rubber (DPNR) wastewater has a high pH and contains high concentrations of organic compounds, particularly biodegradation-resistant compounds such as sodium dodecyl sulfate (SDS), acetone, and suspended residual rubber particles. These compounds hinder the biological treatment of DPNR wastewater using conventional methods. Therefore, this study proposes a pre-treatment method for DPNR wastewater using coagulants such as CaCl₂ and Poly Aluminium Chloride (PAC), prior to biological treatment. The results indicate that using CaCl₂ or PAC at concentrations of 4 and 10 g/l, respectively, effectively removes suspended solids and SDS from the DPNR wastewater. Among these, CaCl₂ at a concentration of 4 g/l achieved the best residual rubber
recovery. The removal efficiencies for COD, SDS, total suspended solids (TS), total nitrogen (TN), and N-NH₄ ⁺ were 92.0, 98.8, 90.1, 58.8, and 64.1%, respectively. After pre-treatment, the wastewater was diluted approximately 15 times and evaluated for its anaerobic biodegradation potential, showing a COD removal efficiency of 48.4% after 7 days at an initial COD of 994±4 mg/l, with a methane production of 125.4 ml/l.