Characterisation of Olive Mill Effluents and Treatments Essays by Sand Filters Followed by Macrophytes Systems

Abstract

Industrial oil olives have a fundamental economic importance for many countries around the Mediterranean Sea. However, during oil olive production, large amount of polluted waters known as olive mill wastewaters (OMW) are generated. Many studies have been undertaken to find efficient treatment systems and several techniques have been tested, but there have been few studies investigating sand filter or macrophytic plants for this type of effluent. The objective of this work is to study of the suitability of macrophytic plants to treat olive mill wastewater (OMW) after their passage through sand filter. The experimental pilot consists of a sand filter followed by a planted system. The sand filter is filled with 50 cm of sand and 10 cm of gravel in the top and the bottom of the filter. The alimentation (4 cm/j) is done sequentially following one day wet /three days dry cycle. In order to activate the degradation processes in the sand filter, OMW are diluted at 50% by domestic wastewater. The second step of the treatment consists of a tank (1x1x1 m3) filled with 20 cm of gravel and 60 cm of soil planted with a mixture of aquatic plants (Phragmites australis, Typha latifolia and Arundo donax) at a density of 25 young plants/m2 and irrigated two times in the week by 20L of preliminary filtered OMW. The obtained results show that the sand filter ensures a neutralization of the OMW pH which passes from 4.79 to 7.68. The enrichment of sand by the micro-organisms makes it possible to have an important mineralization of the organic matter. After ten weeks of operation of this system without clogging sign, the rate of abatement of the TSS, total COD, dissolved COD and phenolic compounds is about 70%, 79%, 76% and 81% respectively. The preliminary outputs by the planted system show a good adaptation of the tested plants to the preliminary treated OMW. The pilot allows an elimination of 94% of TSS, 99.7% of total COD, 99.5% of dissolved COD and 95% of phenolic compounds. With regard to OMW treatment efficiency, the results obtained agree with important role of macrophytes for maintaining the aquatic plants treatment capability particularly for wastewater with high organic matter.