Characterization and recycling of waste water from guayule latex extraction

Abstract

Guayule commercialization for latex production to be used in medical products and other high value applications is now a reality. Currently, wastewater following latex extraction is discharged into evaporation ponds. As commercialization reaches an increased 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 and analyzed for nutrient content, sodium absorption ratio (SAR), and pH. The SAR for W1 indicated it was acceptable for irrigation use. The high SAR values for W2 and W3 indicated they could not be used for irrigation because the high Na content would adversely affect soil properties. The N content of the waste liquid averaged about 0.2%, and the K values were between 500 and 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 the potential for recycling W2 and W3 in the latex extraction process. Results showed that using the treatments comprised of the W2 and W3 waste streams recycled to the extraction process resulted in a lowered SAR of the waste liquid being discharged (26.95–10.5). Based on our results 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 by 50% and the initial amount of extraction solution by 80%. In conclusion, results from this study show that (1) W1 can be used for irrigation after treatment and (2) recycling W2 and W3 for latex extraction is possible.