Kota SATO
Development of Next-Generation Rubber-Processing Wastewater Treatment Technology Consisting UASB and DHS
Takashi YAMAGUCHI
In Southeast Asia, the wastewater drained from manufacturing process of producing natural rubber is treated mainly by stabilization pond methods such as anaerobic lagoons and aerating-oxidation ponds. However, problems of wastewater treatment include that it uses vast aeration electric power and it produces excess sludge in large quantities in the aerating-oxidation pond. In addition, anaerobic lagoon causes methane emission, increasing the greenhouse gas (GHG) load in the atmosphere.
Therefore, in this study, a new treatment process was developed to solve these problems. The process focused on treatment for concentrated rubber latex wastewater, a kind of natural rubber wastewater, it contains high strength sulfate and organic matters.
The system is constituted that combined two-stage UASB (Up-flow anaerobic sludge blanket) reactor as pretreatment with DHS (Down-flow hanging sponge) reactor as post treatment. The first UASB (1st UASB) proceeded methane recovery with sulfate reduction. The second UASB (2nd UASB) produced methane. DHS reactor oxidized remaining organic matters and removed sulfide produced in UASB reactors. In this study, the operating characteristics of the process and an evaluation of the contribution of methanogenic archaea (MA) and sulfate-reducing bacteria (SRB) by activity test are reported. In addition, process performance of the 1s UASB and the aerating-oxidation pond (AP)/settling tank (ST) were compared and estimated the GHG emission and the running cost.As the results, the proposed process combined with two-stage UASB and DHS fed with a latex wastewater (10,200 mgCOD/L) achieved 97.6% of COD removal efficiency with 251 mgCOD/L of effluent treated water under operating conditions of 0.91 kgCOD/m3/d of OLR and 11.1 days of HRT. In the 1st UASB, the hydrogen sulfide concentration of treated water became as high as 151 mgS/L by sulfate reducing action, whereas it was able to maintain 50.1% of methane conversion rate under 1.57 kgCOD/m3/d of OLR. In the 1st UASB fed with latex wastewater with 2.6-9.6 of total COD/sulfate ratio, it was concluded that SRB contributes as hydrogen degrader and MA acts as acetate degrader mainly. Compared with the AP/ST process results, the 1st UASB can reduce GHG emission and running cost by 166% and 132%, respectively.
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