Microbial population dynamics in indigenous olive wastewater biofilms

Abstract

The olive industry in South Africa, although small compared to the rest of the world, is rapidly expanding and producing increased volumes of wastewater on an annual basis that could in future develop into a major environmental problem. Olive mill wastewater (OMWW) and table olive wastewater (TOWW) are characterised by high chemical oxygen demand (COD), biological oxygen demand (BOD) and phenolic content that are toxic to the environment. Due to the nature of olive wastewater (OWW), its irresponsible and unregulated environmental release will result in oxygen depletion, nutrient enrichment and accumulation of toxic compounds in receiving water bodies that ultimately disrupts aquatic and terrestrial ecosystems. An estimated 3500 - 4500 tons of olives are processed on an annual basis by 51 farmers .in the Western Cape. Economic forecasts predict a steady growth, i.e. increased production and processing of olives in the South African olive industry, in the future due to consumer demand. These production increases will consequently lead to increased volumes of wastewater production, which would, in tum, require an expansion of treatment capacity of the wastewater prior to release. Two South African olive factories were chosen for this study: Buffet Olives, situated in Dal Josefat (Paarl), that produces table olives and Vesuvio Estate on Sorento farm (Wellington) that produce extra-virgin olive oil.

Preliminary COD determinations showed that indigenous OWW biofilms within a rotating biological contactor set-up reduced the COD from TOWW and OMWW by 47% and 32%, respectively, over a l0-day period. These preliminary results strongly suggested that biofilms indigenous to OWW have the potential to remediate the pollution problems of OWW. However, the overall aim of this study was to determine how sustainable the application of indigenous biofilms in the OWW are over two production seasons and whether it would be feasible to apply and develop these naturally occurring biofilms as an effective bioremediation tool to reduce the COD and polyphenol content of OWW.