Development of the floating sulphur biofilm reactor for sulphide oxidation in biological water treatment systems

The formation of floating sulphur biofilm was observed in the microbial ecology studies of tannery ponds undertaken by the Environmental Biotechnology Group at Rhodes University. This was related to the steep Redox gradients established at the air/ water interface of anaerobic, organically loaded and actively sulphate reducing systems. This study investigated the potential for applying these observations in developing a floating sulphur biofilm reactor for the removal of sulphide from sulphide-rich effluents produced in wastewater treatment systems. This was carried out in five sequential experimental phases. Where original studies had been undertaken using sulphide-rich water derived from sewage sludge as the carbon source, the successful establishment of a floating sulphur biofilm from effluent of lignocellulose-derived wastewaters had been shown. The effect of influent sulphide concentrations, flow rate and reactor dimensions on the sulphur biofilm formation were investigated for the optimisation of elemental sulphur recovery and sulphide removal efficiency. Polysulphide formation was enhanced by inserting a silicone tube rack and resulted in increased elemental sulphur recovery. Sulphide removal efficiency of 65% and a sulphur recovery of 85% were obtained at the end of the investigation while inter-harvest recovery period of the biofilm was reduced from an initial 4-5 days to 6-12 hours. Water SA Vol. 30 (5) 2005: pp.655-65

Lead mobilisation in the hyporheic zone and river bank sediments of a contaminated stream : contribution to diffuse pollution

Purpose Past metal mining has left a legacy of highly contaminated sediments representing a significant diffuse source of contamination to water bodies in the UK and worldwide. This paper presents the results of an integrated approach used to define the role of sediments in contributing to the dissolved lead (Pb) loading to surface water in a mining-impacted catchment. Materials and methods The Rookhope Burn catchment, northern England, UK, is affected by historical mining and processing of lead ore. Quantitative geochemical loading determinations, measurements of interstitial water chemistry from the stream hyporheic zone, and inundation tests of bank sediments were carried out. Results and discussion High concentrations of Pb in the sediments from the catchment, identified from the British Geological Survey (BGS) Geochemical Baseline Survey of the Environment (GBASE) data, demonstrate both the impact of mineralisation and widespread historical mining. The results from stream water show that the stream Pb load increased in the lower part of the catchment, without any apparent or significant contribution of point sources of Pb to the stream. Relative to surface water, the interstitial water of the hyporheic zone contained high concentrations of dissolved Pb in the lower reaches of the Rookhope Burn catchment, downstream of a former mine washing plant. Concentrations of 56 μg l-1 of dissolved Pb in the interstitial water of the hyporheic zone may be a major cause of the deterioration of fish habitats in the stream and be regarded as a serious risk to the target of good ecological status as defined in the European Water Framework Directive. Inundation tests provide an indication that bank sediments have the potential to contribute dissolved Pb to surface water. Conclusions The determination of Pb in the interstitial water and in the inundation water, taken with water Pb mass balance and sediment Pb distribution maps at the catchment scale, implicate the contaminated sediments as a large Pb supply to surface water. Assessment of these diffuse contaminant sources is critical for the successful management of mining-impacted catchments

Identification of <em>Bacillus subtilis </em>SipW as a Bifunctional Signal Peptidase That Controls Surface-Adhered Biofilm Formation

D ow nloaded from 2 ABSTRACT 21 Biofilms of microbial cells encased in an exopolymeric matrix can form on solid-surfaces, but 22 how bacteria sense a solid surface and up-regulate biofilm genes is largely unknown. We 23 investigated the role of the Bacillus subtilis signal peptidase, SipW, which has a unique role in 24 forming biofilms on a solid surface and that is not required at an air-liquid interface. Surprisingly, 25 we found that the signal peptidase activity of SipW was not required for solid-surface biofilms. 26 Furthermore, a SipW mutant protein was constructed that lacks the ability to form a solid-surface 27 biofilm, but still retains signal peptidase activity. Through genetic and gene expression tests, the 28 non-signal peptidase role of SipW was found to activate biofilm matrix genes specifically when 29 cells were on a solid surface. These data provide the first evidence that a signal peptidase is 30 bifunctional and that SipW has a regulatory role in addition to its role as a signal peptidase. 3