Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 17, 2008
Publication Date: February 1, 2009
Citation: Coffelt, T.A., Williams, C.F. 2009. Characterization and recycling of waste water from guayule latex extraction. Industrial Crops and Products (29), pp. 648-653. Interpretive Summary: Commercialization of guayule as a source of circumallergenic latex for the manufacture of medical and other latex products is becoming a reality. Four potential problems have been identified with the liquid waste stream from latex extraction – 1) an unpleasant odor, 2) negative effects on soil properties due to the high sodium and ammonia concentration in the ammoniated antioxidant solution used in the extraction process, 3) loss of latex in the waste liquid, and 4) treatment and disposal costs. Results from this study showed that the unpleasant odor of the waste streams can be corrected by lowering the pH to <7, negative effects of high Na and ammonia concentration can be overcome by recycling two of the waste streams in the extraction process and pH adjustment followed by clarification of the third waste stream, recycling two of the waste streams will allow recapture of any latex in these waste streams without adversely effecting latex extraction, and recycling would reduce the amount of liquid waste by 50% and replace 80% of the initial extraction solution used during the first processing step. The results from this initial study indicate that the four potential problems associated with the waste streams generated during guayule latex production can be overcome relatively easy and can result in potential beneficial use of the waste streams.
Technical Abstract: Guayule commercialization for latex production to be used in medical products and other applications is now a reality. Currently, waste water following latex extraction is discharged into evaporation ponds. As commercialization reaches full scale, the liquid waste stream from latex extraction will become an environmental and cost issue. The objectives of this study were to 1) evaluate the properties of the liquid waste streams after latex extraction, 2) determine if the waste liquids could be reused, and 3) determine if any of the waste liquid could be recycled for latex extraction. Waste liquid was collected from three waste stream sources (W1 - W3) from the pilot latex extraction facility operated during 2006 then analyzed for nutrient content, sodium absorption ratio (SAR), and pH. The SAR for W1 indicated it was acceptable for irrigation use. Results showed SAR values for W2 and W3 were too high to be used for irrigation because they would adversely affect soil properties. The N content of the waste liquid averaged about 0.2%, and the K values were between 500 - 600 ppm. The solids in W1 and the unpleasant odor characteristic of the waste liquid were overcome by lowering the pH of the waste liquid from over 10 to less than 7. Based on the SAR analyses, six treatments were developed for evaluating recycling W2 and W3 in the latex extraction process. Results showed that using the treatments composed of the W2 and W3 waste streams recycled to the extraction process resulted in a lowered SAR of the waste liquid being discharged (26.95 to 10.5). Results indicated that it might be possible to recover latex from the waste liquid by recycling. More importantly, none of the treatments associated with recycling reduced latex recovery. Reuse and recycling the waste liquids would reduce the amount of waste liquid discharged and the initial amount of extraction solution. In conclusion, results from this study show that, (1) W1 can be used for irrigation with minimal treatment and (2) recycling W2 and W3 for latex extraction is possible.