A tanks-in-series bioreactor to simulate macromolecule-laden wastewater pretreatment under sewer conditions by Aspergillus niger

Sewers are typically a means of transporting wastewater to a treatment facility, with little biotransformation of the soluble polymeric organic matter by suspended biomass. In the interest of providing an effective pretreatment of wastewater in a sewer network, it is necessary to design an accurate tool simulating sewer conditions and introduce an appropriate biomass for macromolecular pollutant degradation. Such a model reactor was built using a tanks-in-series design and the degradation of a polysaccharide (starch) by Aspergillus niger MUCL 28817 was studied. Starch degradation and the accumulation of intermediates (hydrolysis fragments) in the individual reactors were quantified under transient conditions, at a mean hydraulic residence time of 17 h. Starch was degraded by 90% in this reactor system and an accumulation of oligosaccharides with molecular weight lower than 1,000 Da was observed. These results may be helpful in the development of wastewater treatment in sewers and in the alleviation of the burden on undersized wastewater treatment systems.     

Prevalence of blindness and visual impairment in the region of Ségou, Mali. A baseline survey for a primary eye care programme

A community-based cross-sectional study on the prevalence and causes of blindness and visual impairment was conducted between July and August 1990 in three rural districts in Ségou region, Mali. The study population consisted of 5871 villagers. In the study area, the overall prevalence of bilateral blindness was 1.7% (standardized rate for age 2.0% +/- 0.4%), of bilateral visual impairment 1.7% (2.1% +/- 0.4%), of unilateral blindness 1.7% (2.2% +/- 0.4%) and of unilateral visual impairment 1.0% (1.2 +/- 0.3%). No important differences were found between districts. Cataract was the most common cause of visual loss (54%) and was most prevalent among those over 50 years of age. In 43%, unilateral blindness was associated with trauma. Other major eye diseases accounting for high percentages of visual impairment were trachoma and glaucoma. Xerophthalmia appeared to be a major public health problem among children in the age group 0-5. It was concluded that blindness is a major public health problem in this region. Some recommendations are given for strengthening integrated primary eye care at the district level in Ségou region.