Kotaro HORISAWA
Treatment of Natural Rubber Latex Wastewater from Deproteinization Process
Takashi YAMAGUCHI
Natural rubber is natural resources, which has better solid-state properties than synthetic rubber. But it has a demerit that allergy-producing proteins remain in finished natural rubber products. Therefore it has investigated that the deproteinization method of natural rubber latex, and then the low-cost and highly-efficient method was developed. But high-rate organic wastewater that contained high-rate surfactant (sodium dodecyl sulfate: SDS) are discharged from this method. 1st wastewater and 2nd wastewater that composition is different each are discharged from centrifugal process. A total amount of the discharge is double of provided deproteinized natural rubber latex (DPNR latex). The wastewater has been disposed as industrial waste. Therefore, a treatment system is required to treat this wastewater directly in the deproteinization factory. The objective of this study was to develop the treatment system using anaerobic treatment method. We investigated applicability of anaerobic treatment and the effect of SDS to treat natural rubber wastewater.
By batch test with vial, biodegradability of 1st wastewater is indicated from the result of methane conversion rate of 1st wastewater is achieved to about 25% in 12 days. However, by sequential treatment used lab-scale UASB reactor, it is revealed that the rubber particles that are contained in wastewater coagulated in the treatment system. Therefore, it is indicated that the necessary to remove remained rubber from wastewater. And recovering remained rubber in the wastewater may prove to be an effective use of resources.
But the natural rubber latex containing high concentration of SDS didnÉÕ coagulate at pH 4.8 (an isoelectric point of the rubber particle). For this reason, it was shown that high concentration SDS stabilizes the dispersibility of the rubber particles and interferes with rubber recovery. And to coagulate the rubber particles by reducing pH, we need to reduce the SDS concentration to 100 mg/L or fewer.
The result of the effect of SDS to methane activity, it was observed that methane activity rate was reduced relative to increase of SDS loading per sludge concentration (SDS/M, g-SDS/g-VS) regardless of sludge concentration. And we need to reduce SDS/M to 0.01 or less to keep the methane activity rate above 90%
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