Occurrence, removal and accumulation in sludge of protozoan cysts and helminth eggs in a full-scale anaerobic pond in Burkina Faso.

The present paper investigates the occurrence, removal, and accumulation of protozoan cysts and helminth eggs in a large anaerobic pond treating municipal wastewater of Ouagadougou (Burkina Faso). With a hydraulic retention time of 6.5 days, the anaerobic pond achieved 100% removal of helminth eggs and protozoan cysts most of the time, except during the hot period. The average residual concentrations of helminth eggs and protozoan cysts in the effluent were respectively 0.45 eggs/L (minimum 0 and maximum 3), and 5.4 cysts/L (minimum 0 and maximum 26). Protozoan cysts accumulation in sludge averaged 1,613 cysts/g total solids. Ancylostoma duodenale, Ascaris lumbricoides and Hymenolepis nana were the main helminth species found in the sludge. After 7 years of operation, the sludge in the pond still contained a high level of viable helminth eggs evaluated at 42%.

Electrocoagulation for the treatment of textile wastewaters with Al or Fe electrodes: compared variations of COD levels, turbidity and absorbance.

Electrocoagulation technique has been used for the treatment of two wastewaters issued by textile industry. Treatment was carried out in a discontinuous system provided with aluminium or iron electrodes, and with recirculation of the liquid. The efficiency of the technique was followed depending on the electrode material in terms of water treatment, current efficiency of the dissolution, cell voltage, energy consumption to reach the same COD or turbidity abatement: regardless of the quality of the phase separation in the flocculation section downstream of the electrocoagulation cell, the two metals were found to be of comparable efficiency. Besides COD and absorbance were shown to follow similar, regular variations along the treatment; experimental data could be interpreted by a simple model involving the overall equilibrium between the metal dissolved--in the form of hydroxides--and the polluting substance. Abatement of the waste turbidity was observed to obey another law, with a sharp reduction of turbidity after a preliminary phase, where accumulation of metal hydroxide has no effect on this variable.