Feasibility of a multi-component additive for efficient control of activated sludge filamentous bulking.

Instantaneous improvement of the settling of bulking filamentous activated sludge can be achieved by the addition of a polymer or a large amount (up to 100% of the MLSS concentration) of talc powder to the sludge. Long-term improvement relies on repeated additions, as these additives have no adverse effects on the causative filaments. A multi-component additive was compared to the traditional additives in lab-scale activated sludge units using three highly filamentous sludges from different industrial treatment plants. The study demonstrated that the multi-component additive was superior to the traditional remedies. It was shown that, in the case of severe filamentous bulking, a single addition of the new additive immediately improved sludge settling and exerted a destructive effect on the causative filamentous bacteria. Thus, the latter additive also ensured a long-term sludge sedimentation improvement. The traditional additives exhibited an immediate and short-term effect. The novel additive also retarded sludge rising due to denitrification and it improved sludge dewaterability. The study revealed Nostocoido limicola II, with slightly hydrophobic cell wall, to be somewhat resistant to the quaternary ammonium salt present as biocide in the additive.

Enhancing the start-up of a UASB reactor treating domestic wastewater by adding a water extract of Moringa oleifera seeds.

Water extract of Moringa oleifera seeds (WEMOS) was used to enhance the start-up of a self-inoculated upflow anaerobic sludge blanket (UASB) reactor treating raw domestic wastewater. Two reactors labelled control (RC) and WEMOS addition (RM) were started without special inoculum. Both reactors were fed continuously for 22 weeks with domestic wastewater containing an average total chemical oxygen demand (COD) of 320 mg O2/l and suspended solid (SS) of 165 mg/l. The reactors operated during the entire experimental period at 29 degrees C and at a hydraulic retention time (HRT) of 4 h. The RM reactor received 2 ml WEMOS per litre of influent. WEMOS solution was prepared on the basis of 2.5% (w/v) ground M. oleifera seeds in water. The results of 22 weeks' operation showed an improvement in the performance of the RM compared to that of the RC. The dosage of WEMOS in the feed (1) shortened the biological start-up period by 20%, (2) increased acidogenic and methanogenic activity by a factor of 2.4 and 2.2 respectively, (3) increased the specific biogas production by a factor of 1.6, (4) favoured fast growth of the sludge bed, and (5) allowed the aggregation of coccoid bacteria and growth of microbial nuclei, which are precursors of anaerobic granulation.

Smear positive pulmonary tuberculosis in a prison setting: experience in the penal camp of Bouaké, Ivory Coast.

SETTING: Bouaké prison camp, Ivory Coast. OBJECTIVE: To determine the clinical, radiographic and therapeutic characteristics of smear-positive pulmonary tuberculosis in the prison camp of Bouaké. METHODS: The study included 108 cases of smear positive pulmonary tuberculosis who had never been treated previously. Triple chemotherapy of 6 months' duration was recommended for all of the patients. RESULTS: The incidence of smear positive tuberculosis in the prison population under study was very high (5.8%). In the majority of cases tuberculosis infection is associated with other conditions: here they were malnutrition (75%), anaemia (70%) and dermatoses (64%). Human immunodeficiency virus (HIV) infection was observed in 30% of the cases, and alcohol and tobacco dependence in 50%. Radiographic lesions were extensive in 70% of the cases. The 6-month treatment regimen is still effective: 80 of the 108 (74.1%) were cured, i.e. 97.6% of those who completed their treatment. The death rate, however, was alarming at 24% (one patient in four). The main reason for incarceration was theft (73%). CONCLUSION: Other epidemiological studies are needed urgently in order to pin-point those factors that favour the progression from tuberculous infection to disease in this very specific setting, and to improve socio-sanitary conditions for prison inmates.

[Prevalence of asthma and respiratory diseases in schools in Bouake (Ivory Coast): preliminary results]. / Prévalence de l'asthme et des maladies respiratoires en milieu scolaire à Bouake (Côte d'Ivoire): résultats préliminaires.

Using an auto-administered questionnaire, a cluster sample survey was carried out in January 1990 among 2433 secondary schoolchildren in Bouake (Cote d'Ivoire). The prevalence rate of asthma was fairly high (10.8%), as well as that of wheezing (19.8%), dyspnea (42.8%), broncho-pulmonary diseases (25.8%) and smoking habit (14.5%). The results are discussed with regard to the published data.