Development of appropriate technology for treatment of molasses-based wastewater

Abstract

In this study, the performance of a proposed treatment system consisting of an anaerobic process (acidification, methane fermentation) and an aerobic process (trickling filter) was evaluated for treating high concentrations of molasses-based wastewater (43–120 gCOD/L) by a continuous flow experiment. An anaerobic up-flow staged sludge bed (USSB) reactor, equipped with multiple gas solid separators, was used as the main treatment/methane recovery process. The USSB showed good efficiency of both COD removal (80–87%) and methane recovery (70–80%) at an organic loading rate of 11–43 kgCOD/m³ day. As the influent COD concentration was increased, the organic loading rate for stable operation of the USSB was reduced due to cation inhibition. However, the COD removal efficiency of the whole treatment system (including the aerobic post-treatment process) was 96% even at an influent COD concentration of 120 gCOD/L. Use of the treated wastewater as a fertilizer and/or irrigation-water for sugarcane was evaluated by a field cultivation test. Both growth of sugarcane and emission of greenhouse gases from the field soil were measured. A relatively high methane flux (352 μgCH₄/m² h) was observed when the treated wastewater from day 0 was used. By day 3, however, this value was reduced to the same level as the control. In addition, growth of sugarcane was satisfactory when the treated wastewater was used. The treated wastewater was found to be useful for cultivation of sugarcane in terms of both a low risk of greenhouse gas emission from the field soil and effectiveness for growth of sugarcane.

Keywords:

• Methane fermentation
• molasses-based wastewater
• greenhouse gas
• sugarcane
• irrigation

Acknowledgment

This study was supported by a NIES special research program.