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 cacl2 at ca2+/sds and ca2+/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 kgcod·m-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 kgcod·m-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.