Biodegradation of olive mill wastewater by two bacterial strains

Abstract

Wastewater from olive mill is a by-product of olive oil production, that is a serious environmental problem in many Mediterranean countries. The production of large quantities of waste in a short period of time together with the high organic load and high toxicity of the waste make it difficult to deal with the problem. Phenolic compounds are one of the main factors responsible for the toxicity of olive mill wastewater (OMW). In the present work, two selectively anaerobic bacteria, Sporolactobacillus spp. and Rhodopseudomonas spp. isolated from compost tea were used. These two strains were tested for their ability to reduce the BOD5 and COD levels and to degrade polyphenols responsible for the toxicity of OMW. The two strains were able to grow on a dilution of a natural OMW and largely degrade the polyphenols. The dilution depended on the initial COD value of the waste. After 90 days of treatment reduction over 70% was observed in all three parameters which were measured while in an additional sampling that carried out in the 150th day, the reduction of BOD5, COD and total phenols concentration, reached to 96.1%, 81.8% and 75.1% respectively. Additionally, an increase in the pH was observed, moving from acidic to slightly alkaline. All these features make the two strains attractive candidates for the development of a biotechnological process for the biodegradation of OMW.