Effluent quality of a conventional activated sludge and a membrane bioreactor system treating hospital wastewater.

Two lab scale wastewater treatment plants treating hospital wastewater in parallel were compared in terms of performance characteristics. One plant consisted of a conventional activated sludge system (CAS) and comprised an anoxic and aerobic compartment followed by a settling tank with recycle loop. The second pilot plant was a plate membrane bioreactor (MBR). The wastewater as obtained from the hospital had a variable COD (Chemical Oxygen Demand) ranging from 250 to 2300 mg l(-1). Both systems were operated at a similar hydraulic residence time of 12 hours. The reference conventional activated sludge system did not meet the regulatory standard for effluent COD of 125 mg l(-1) most of the time. Its COD removal efficiency was 88%. The plate MBR delivered an effluent with a COD value of 50 m g l(-1) or less, and attained an efficiency of 93%. The effluent contained no suspended particles. In addition, the MBR resulted in consistent operational parameters with a flux remaining around 8-10 l m(-2) h(-1) and a trans membrane pressure < 0.1 bar without the need for backwash or chemical cleaning. The CAS and the MBR system performed equally well in terms of TAN removal and EE2 removal. The CAS system typically decreased bacterial groups for about 1 log unit, whereas the MBR decreased these groups for about 3 log units. Enterococci were decreased below the detection limit in the MBR and indicator organisms such as fecal coliforms were decreased for 1.4 log units in the CAS system compared to a 3.6 log removal in the MBR.

Incidence and management of oral conditions in general practice.

Despite a high community prevalence, little is known about the occurrence of oral conditions in general practice. In an observational study, 354 new cases of oral complaints were recorded in 35 participating practices during a period of six months (cumulative incidence = 6.7 per 1000 per year). The incidence was highest in children under five years of age (21% of all cases). The conditions diagnosed most frequently were aphthous ulceration, oral candidiasis, and herpes simplex infection. Most oral conditions were minor ailments, and could be dealt with by the general practitioner alone.