Reduction of alkali supplement in a pilot-scale thermophilic multi-staged UASB reactor treating alcohol distillery wastewater

One of the main disadvantages of anaerobic wastewater treatment at a low pH is the significant operational cost due to the addition of necessary alkali. To reduce alkali supplement and thus the cost, this study proposes a sequential multi-feed [SqMF] mode [distributed feeding] and effluent recycle [ER] mode. Experiments were conducted with a pilot-scale [2.5 m[3]] thermophilic [55°C] multi-staged up-flow anaerobic sludge blanket reactor. Alcohol distillery wastewater [shochu], a major source of industrial wastewater in Japan, was used for the study. The SqMF mode of operation [influent pH: 5.0; organic loading rate: 45 kgCOD/m[3]/day; HRT: 12 hours; influent COD concentration: 20,900 mgCOD/L] successfully reduced the alkali supplement [24% NaOH solution] requirement by 67.2% compared with the single-feed mode. For the ER mode operation [organic loading rate: 35 kgCOD/m[3]/day; HRT: 12 hours; influent COD concentration: 17,400 mgCOD/L], operation was possible without any alkali supplement since the system uses the alkalinity generated during microbial metabolism

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

Intermittent effluent recirculation for the efficient treatment of low strength wastewater by an EGSB reactor

In order to establish the appropriate methane fermentation technology for low strength wastewater, a 2.0 L EGSB reactor was operated at 20°C with 0.3 - 0.4 g COD/L of sucrose-based synthetic wastewater for 500 days. At the start up period, the reactor was operated in EGSB mode with a 5 m/h up flow velocity by continuous effluent recirculation. However, the EGSB reactor exhibited insufficient COD removal [50-60%] at COD loading of 7.2 - 9.6 kg COD/m3.day due to the low COD concentration in the sludge bed. Therefore, we proposed the new operation mode by switching to UASB mode [without recirculation, 0.7 m/h up flow velocity] for 30 minutes and EGSB mode for 10 minutes in 40 minutes cycle. Moreover we added sodium sulfide to make the low ORP condition. In this operation, COD removal increased dramatically, from 65% to 91%. Additionally, physical properties of the retained sludge were well maintained in this operation mode. Furthermore, the retained sludge possessed appropriate levels of methanogenic activity [0.2-0.4 g COD/g VSS/day] at 20°C