Rubber and methane recovery from deproteinized natural rubber wastewater by coagulation pre-treatment and anaerobic treatment

A newly developed natural rubber deproteinization process produces deproteinized natural rubber [DPNR] wastewater as an intermediate product containing a high concentration of sodium dodecyl sulfate [SDS] and rubber. In this study, a novel process to recover the residual rubber and energy as methane from DPNR wastewater was developed. As a pretreatment, SDS and residual rubber in DPNR wastewater were coagulated and recovered by addition of CaCl[2] at Ca[2+]/SDS and Ca[2+]/rubber mass ratios of 0.070 and 0.055, respectively. The remaining organic matter in the pre-treated DPNR wastewater was converted to methane by using a mesophilic up-flow anaerobic sludge bed [UASB] reactor. The UASB reactor with the diluted pre-treated DPNR wastewater showed a total chemical oxygen demand [COD] removal efficiency of 92 +/- 2% at a maximum loading rate of 6.8 +/- 1.8 kgCODm[-3]d[-1] at a hydraulic retention time [HRT] of 12 h. Under the condition of effluent recirculation with raw pre-treated DPNR wastewater, the UASB reactor showed a total COD removal efficiency of 84 +/- 8% at the maximum loading rate of 6.4 +/- 1.7 kgCODm[-3]d[-1] at HRT of 39 h. The results suggest that the newly developed resource recovery process for DPNR wastewater could be a promising treatment system

Evaluation of treatment characteristics and sludge properties in a UASB, reactor treating municipal sewage at ambient temperature

The evaluation of treatment characteristics and sludge properties of an upflow anaerobic sludge blanket [UASB] process was investigated using a pilot-scale 1.15 m[3]reactor. The UASB, inoculated with digester sludge, was operated at a hydraulic retention time of 8 h at sewage temperatures ranging from 10.6 to 27.7 °C for more than 1100 days. The stable removal efficiencies for total COD[Cr] and SS were 63 +/- 13% and 66 +/- 20%, respectively. The average concentration of the retained sludge increased to more than 24.5 gSS/L of the column volume after two years of operation. In summer, the water temperature increased above 20 °C, and biodegradation of solid organic matter was enhanced. The solid retention time was evaluated to be as long as 293 +/- 114 days; this is sufficient for mineralisation of solid organic matter, as indicted by a low sludge conversion of 0.029 gVSS/gCOD[removed] and a growth yield of 0.132 gVSS/gCOD, determined by seasonal sludge profiling. The bacterial communities, based on bacterial 16S rRNA genes in the retained sludge, were significantly diverse. Bacteroidetes and Firmicutes were the dominant phyla of the decomposers of solid organic matter in the library. A Ruminocoecus-related clone detected in the Firmicutes phylum acted as a cellulose decomposer