Presence of parasitic protozoa and helminth in sewage and efficiency of sewage treatment in Tunisia.

Helminth eggs and protozoan cysts were enumerated in raw and treated wastewater in Tunisia in order to determine their removal by wastewater treatment and to provide quantitative data for developing regulations for wastewater quality that are currently lacking. Raw and treated wastewater samples were collected from 17 plants in Tunisia during 2006-2007 and analyzed for parasites using the modified Bailenger method. Two groups of parasites, namely, Ascaris sp., Entamoeba coli, Enterobius vermicularis, and Taenia sp. (group 1) and Entamoeba histolytica/dispar, Giardia sp., and Taenia sp. (group 2) could statistically be distinguished according to their removal by wastewater treatment. Group 1 parasites were removed by 1.1 log(10) (92.4%) and group 2 parasites by 0.61 log(10) (76%). The ubiquitous presence of parasitic protozoa in Tunisian wastewater and ineffective wastewater treatment lead to their proliferation in surface waters with a high probability of exposure of human and animals to these parasites and consequent adverse health effects, as is apparent from epidemiologic data as well. This study provides a quantitative basis for risk assessment studies and development of mitigation strategies, such as improving wastewater treatment efficiency.

Use of Geotrichum candidum for olive mill wastewater treatment in submerged and static culture.

The production of lignin peroxidase (LiP), manganese peroxidase (MnP) and lipases by Geotrichum candidum were performed in order to control the decolourisation and biodegradation of olive mill wastewater (OMW). Optimisation of different factors showed that dilution, carbon and ammonium concentrations significantly affected decolourisation and activities of ligniolytic peroxidases (LiP and MnP) on OMW. Moreover, addition of olive oil and agitation improved the lipase production. Batch and continuous OMW treatments in settler or bubble column bioreactors showed high COD and colour removal efficiencies of 60% and 50%, respectively. Lipolytic activity was greater in the batch bubble column whereas, LiP and MnP productions were improved in the settler. The performance of the continuous processes decreased with the decrease of hydraulic retention time (HRT). It has been shown that decolourisation and biodegradation decreased with an average of 40% and 45%, respectively, by decreasing the HRT from 4d to 1.7d.

Ecological removal of recalcitrant phenolic compounds of treated olive mill wastewater by Pediococcus pentosaceus.

Treatment of olive mill wastewater by different biological process led to an important decrease of organic compounds but the black coloration due to the recalcitrant phenolic compounds persists. Experimental design using fractional factorial plan showed that, among the seven studied factors, yeast extract, dilution and glucose exhibited a positive effect on Pediococcus pentosaceus growth and treated olive mill wastewater (TOMW) decolourisation. Optimization of influent factors showed that 2.5 and 1g/l are the suitable concentrations of glucose and yeast extract, respectively. Optimum TOMW decolourisation was reached when TOMW was diluted to 2.5 initial OD390 value. The growth of P. pentosaceus on TOMW led to high molecular weight phenolic compounds removal as shown by the sephadex G-50 chromatogram. Simple phenolic compound removal was also observed. Bacterial growth on TOMW induced an ecological removal of recalcitrant phenolic compounds without chemical sludge production.

Involvement of lignin peroxidase in the decolourization of black olive mill wastewaters by Geotrichum candidum.

AIM: Decolourization of black olive mill wastewaters (OMW) by depolymerization of phenolic compounds by Geotrichum candidum. METHODS AND RESULTS: Our results show that G. candidum is able to grow on black OMW supplemented with carbon source and nitrogen. The Geotrichum growth decreased the pH and induced a 49% of colour removal when the black OMW was supplemented with glycerol and diammonium tartrate (20 mm ammonium). An improvement of 10% of colour removal was observed when the culture was supplemented with veratryl alcohol. The decolourization was inhibited with glutamate as nitrogen source. CONCLUSION: Our results suggest the potential use of G. candidum in black OMW decolourization and support the concept that lignin peroxidase (LiP) of G. candidum is involved in the depolymerization of phenolic compounds. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report of LiP production by G. candidum on OMW.