Biosorptive recovery of platinum from platinum group metal refining wastewaters by immobilised Saccharomyces cerevisiae.

The process of platinum group metal (PGM) refining can be up to 99.99% efficient at best, and although it may seem small, the amount of valuable metal lost to waste streams is appreciable enough to warrant recovery. The method currently used to remove entrained metal ions from refinery wastewaters, chemical precipitation, is not effective for selective recovery of PGMs. The yeast Saccharomyces cerevisiae has been found capable of sorbing numerous precious and base metals, and is a cheap and abundant source of biomass. In this investigation, S. cerevisiae was immobilised using polyethyleneimine and glutaraldehyde to produce a suitable sorbent, capable of high platinum uptake (150-170 mg/g) at low pH (<2). The sorption mechanism was found to be a chemical reaction, which made effective desorption impossible. When applied to PGM refinery wastewater, two key wastewater characteristics limited the success of the sorption process; high inorganic ion content and complex speciation of the platinum ions. The results proved the concept principle of platinum recovery by immobilised yeast biosorption and indicated that a more detailed understanding of the platinum speciation within the wastewater is required before biosorption can be applied. Overall, the sorption of platinum by the S. cerevisiae sorbent was demonstrated to be highly effective in principle, but the complexity of the wastewater requires that pretreatment steps be taken before the successful application of this process to industrial wastewater.

Retrospective analysis of the ethnic origins of male British army soldiers with peripheral cold weather injury.

OBJECTIVES: To determine if African Americans, Pacific Islanders and Gurkhas have a different incidence and severity of peripheral cold injury when compared to Caucasians in the British Army. METHOD: The design was a retrospective analysis of those British male army personnel aged over 18 assessed at the Institute of Naval Medicine Cold Injury Clinic. The participants were 311 patients assessed on first attendance at the UK Institute of Naval Medicine. RESULTS: After excluding those classed as normal, African Americans had a relative incidence of 30.36 (95% CI 25.82 -35.70) when compared to Caucasians; Pacific Islanders a relative incidence of 2.58 (CI 1.24 - 5.38), again against Caucasians. Being of Gurkha ethnicity proved protective, with no abnormal cases found on assessment. The African Americans were more severely affected than Caucasians, with mean scores of 5.39 (SD 1.767) against 4.24 (SD 1.994) for Caucasians. The severity of Pacific Islanders were similar to Caucasians. The ages of African Americans, Pacific Islander and Caucasians had similar means of 26.05, 26.30 and 26.68 respectively, but with a broader age range for Caucasians; SDs 3.428, 2.958 and 7.735. CONCLUSION: Young male African Americans in the British Army are at 30 times greater chance of developing peripheral cold injury and are more severely affected than their Caucasian counterparts following similar climatic exposure, using similar clothing and equipment. Pacific Islanders are at a 2.6 times increased risk, while being a Gurkha is protective.

Bioremediation of a wine distillery wastewater using white rot fungi and the subsequent production of laccase.

The aim of this work was to ascertain whether a submerged culture of a white rot fungus could be used to treat distillery wastewater, and whether the compounds present in the wastewater would stimulate laccase production. Trametes pubescens MB 89, Ceriporiopsis subvermispora, Pycnoporus cinnabarinus and UD4 were screened for their ability for the bioremediation of a raw, untreated distillery wastewater as well as distillery wastewater that had been pretreated by polyvinylpolypyrrolidone. Suitability of each strain was measured as a function of decreasing the chemical oxygen demand (COD) and total phenolic compounds concentration and the colour of the wastewater, while simultaneously producing laccase in high titres. After screening, T. pubescens MB 89 was used further in flask cultures and attained 79 +/- 1.1% COD removal, 80 +/- 4.6% total phenols removal, 71 +/- 1.6% decrease in colour at an absorbance of 500 nm and increased the pH from 5.3 to near-neutral. Laccase activity in flask cultures peaked at 4,644 +/- 228 units/l, while the activity in a 50 l bubble lift reactor peaked at 12,966 +/- 71 units/l. Trametes pubescens MB 89 greatly improved the quality of a wastewater known for toxicity towards biological treatment systems, while simultaneously producing an industrially relevant enzyme.

Bioremediation of trace organic compounds found in precious metals refineries' wastewaters: a review of potential options.

Platinum group metal (PGM) refining processes produce large quantities of wastewater, which is contaminated with the compounds that make up the solvents/extractants mixtures used in the process. These compounds often include solvesso, beta-hydroxyxime, amines, amides and methyl isobutyl ketone. A process to clean up PGM refinery wastewaters so that they could be re-used in the refining process would greatly contribute to continual water storage problems and to cost reduction for the industry. Based on the concept that organic compounds that are produced biologically can be destroyed biologically, the use of biological processes for the treatment of organic compounds in other types of waste stream has been favoured in recent years, owing to their low cost and environmental acceptability. This review examines the available biotechnologies and their effectiveness for treating compounds likely to be contained in precious metal extraction process wastewaters. The processes examined include: biofilters, fluidized bed reactors, trickle-bed bioreactors, bioscrubbers, two-phase partitioning bioreactors, membrane bioreactors and activated sludge. Although all processes examined showed adequate to excellent removal of organic compounds from various gaseous and fewer liquid waste streams, there was a variation in their effectiveness. Variations in performance of laboratory-scale biological processes are probably due to the inherent change in the microbial population composition due to selection pressure, environmental conditions and the time allowed for adaptation to the organic compounds. However, if these factors are disregarded, it can be established that activated sludge and membrane bioreactors are the most promising processes for use in the treatment of PGM refinery wastewaters.

Biosorption of precious metals.

Biosorption has emerged as a low-cost and often low-tech option for removal or recovery of base metals from aqueous wastes. The conditions under which precious metals such as gold, platinum and palladium are sorbed by biomass are often very different to those under which base metals are sorbed. This, coupled with the increasingly high demand for precious metals, drives the increase in research into efficient recovery of precious metal ions from all waste material, especially refining wastewaters. Common biosorbents for precious metal ions include various derivatives of chitosan, as well as other compounds with relatively high surface amine functional group content. This is generally due to the ability of the positively charged amine groups to attract anionic precious metal ions at low pH. Recent research regarding the biosorption of some precious metals is reviewed here, with emphasis on the effects of the biosorption environment and the biosorption mechanisms identified.

Characterization of Thiobacillus thioparus isolated from an activated sludge bioreactor used for hydrogen sulfide treatment.

AIMS: To compare Thiobacillus thioparus population dynamics in a control and a test activated sludge (AS) bioreactor, used for hydrogen sulfide (H(2)S) degradation. METHODS AND RESULTS: Denaturing gradient gel electrophoresis (DGGE) was used to confirm the presence of T. thioparus, and real-time PCR was used to quantify the level of this bacterium in the AS samples. The DGGE analysis showed a band for T. thioparus in all samples, with the band being more prominent in the test sample with H(2)S diffusion. It also showed that although a change occurred in the diversity of the microbial population in the test sludge after 6 weeks of H(2)S diffusion, the microbial community structure of the test and control was still similar. Thiobacillus thioparus-specific PCR primers confirmed that 50% of the isolates from both the test and control bioreactors were T. thioparus. The thiobacilli population became more efficient at degrading the diffused H(2)S. This increase in efficiency was confirmed by a significant increase in the number of isolates from the test sludge compared with those from the control sludge, when they were grown in a thiosulfate-rich liquid medium. CONCLUSIONS: It was concluded that the use of AS process for H(2)S removal encourages the population of T. thioparus to increase even at times when the total biomass concentration shows a decrease. SIGNIFICANCE AND IMPACT OF THE STUDY: The research results give an insight into the dynamics of the microbial population in an AS pilot plant used in a dual role, to treat the wastewater and H(2)S.

Performance of dead Azolla filiculoides biomass in Biosorption of Au from wastewater.

Dried milled biomass of Azolla filiculoides removed up to 98.2% of gold from wastewater from a gold plating factory containing 5 mg gold/l in solution in batch biosorption. The gold uptake capacity of the biomass was 98 mg/g. Whole dried biomass used in a continuous flow column removed up to 100% of gold from diluted wastewater. A similar column was linked to a sulphide precipitation process to provide a two-step system which was able to remove 98% of gold from undiluted wastewater containing 41 mg Au/l. The lifetime of the column was five days.

Withstanding shock loads in activated sludge treatment by pre-exposure to low H2S concentrations.

An activated sludge pilot plant was used to acclimatise sludge to a low dose of H2S gas. Sludge samples from different types of treatment works were compared with acclimatised and unaclimatised sludges using batch absorption tests. The effects of sludge source and acclimatisation on the ability of the sludge to withstand shock loads of 50 ml l(-1) H2S were evaluated. Sludge that had been acclimatised to 5 ml l(-1) H2S in the air supply removed 70% of a 50 ml l(-1) load in a batch reactor after three sludge ages of acclimatisation. Pre-exposure to low H2S concentrations enabled the bacterial community to maintain a sufficient sulphide-degrading population to retain acclimatisation and degrade subsequent high loads which are toxic to unacclimatised sludge. Acclimatisation to H2S is therefore mainly an effect of selection pressure on the mixed bacterial population, which suggests that the H2S removal capacity of different types of activated sludge will converge after acclimatisation, irrespective of their initial degradative abilities.

The enzymology of sludge solubilisation utilising sulphate-reducing systems: the properties of lipases.

The first stage in the degradation and recycling of particulate organic matter is the solubilisation and enhanced hydrolysis of complex polymeric organic carbon structures associated with the sulphidogenic environment. An investigation into the enzymology of these processes has shown that lipase enzyme activities were found predominantly associated with the organic particulate matter of the sewage sludge. Sonication of the sludge gave an increase in enzyme activity as the enzymes were released into the supernatant. pH and temperature optimisation studies showed optima between 6.5 and 8 and 50-60 degrees C, respectively. All the lipase enzymes from the methanogenic bioreactors indicated extensive stability for at least an hour at their respective optimum temperatures and pH; sulphidogenic lipases reflected limited stability at these temperatures and pH during this time period. Though sulphate showed inhibitory properties towards lipases both sulphide and sulphite appeared to enhance the activity of the enzymes. It is argued that these sulphur species, liberated at different times during the sulphate reduction process, disrupt the integrity of the organic particulate floc by neutralising acidic components on the surface. The release of further entrapped enzymes from the organic particulate matter result in a subsequent enhancement of hydrolysis of polymeric material.

Dinitrogen oxide production by a mixed culture of nitrifying bacteria during ammonia shock loading and aeration failure.

A number of experiments was conducted in order to establish if N(2)O in the exhaust gas from an aerobic consortium of nitrifiers could be used as an indicator for monitoring the nitrification process. Laboratory-scale experiments with an activated sludge system showed a strong correlation between ammonia shock loads and both the concentration of N(2)O and the rate of increase of N(2)O in the exhaust gas for shock loads less than 1.60 mg ammonical nitrogen (NH(3)-N) per g total suspended solids (TSS). For greater ammonia shock loads, correlation was found between build-up of nitrite in the aeration tank and the concentration of N(2)O in the exhaust gas from the tank. When subjecting the system to aeration failure, a similar pattern was seen, with a correlation between nitrite build-up in the aeration tank and increases in the concentration of N(2)O in the exhaust gas. The results from this work suggest that the changes in N(2)O concentration in the exhaust gas from a nitrifying process may be a useful parameter for monitoring such processes.

Dinitrogen oxide detection for process failure early warning systems.

A number of experiments were conducted in order to establish whether the concentration of N2O in the off-gas from an activated sludge pilot plant could be used as a indicator for monitoring the nitrification process and as an early indication of ammonia appearing in the plant effluent. A strong correlation was found between ammonia shock loads and the concentration of N20 in the off-gas from the aeration tank for ammonia shock loads and dissolved oxygen depletion. When subjecting the experimental setup to doses of a nitrification inhibitor (allylthiourea) a similar pattern was seen with a correlation between nitrite build up in the aeration tank and concentration increase of N2O in the off-gas from the aeration tank. The results from this work suggest the concentration and the changes in the concentration of N2O in the exhaust gas from a nitrifying process may be a useful parameter for monitoring nitrifying activated sludge processes.

Nutrient addition to enhance biological treatment of greywater.

This study compares the chemical oxygen demand (COD) removal and respiration rates of a microbial population treating real and synthetic greywaters dosed with nutrient supplements. The nutrient composition of the real and synthetic greywaters was analysed and the dosing regime for nitrogen, phosphorus and a range of trace metals planned accordingly. The doses consisted of eight single additives (macronutrients and trace metals) to the control greywater and six trace metal additions to C: N : P balanced greywater. The COD removal for the control real and synthetic greywater in lab-scale activated sludge systems (0.038 and 0.286 kg COD kg MLSS(-1) d(-1), respectively) confirmed nutrient limitation and the poor degree of greywater treatment. Nutrient dosing increased the COD removal rate and oxygen uptake rate in many cases. The greatest stimulation of microbial activity was observed with zinc additions to C: N: P balanced real greywater (1.291 kg COD kg MLSS(-1) d(-1) over 30 times the control). Inhibitory effects to various extents were rare and limited mainly to the additions of metals to synthetic greywater. The dominance of chemicals effects was observed on addition of some micronutrients; notably iron and aluminium, metals on which many coagulants for use in biotreatment of other wastewaters are based. The data indicate that the impact of understanding microbial processes and the nutrients required for wastewater treatment can only serve to optimise process efficiency for the proposed treatment of greywater.

Simultaneous activated sludge wastewater treatment and odour control.

Lab-scale tests were used to determine the amount of H2S that can be treated using a range of different activated sludges. Static vessels were used to study the effects of different H2S concentrations (5, 25, 50 and 75 ppm). The data indicated that odour control may be carried out using certain types of sludge, but sludge type, e.g. carbonaceous, nitrifying, with or without coagulant, affects removal efficiency. The presence of the biomass resulted in greater H2S removal than the use of wet scrubbing and the adverse effects on mixed liquor were negligible. A pilot plant was used to study the removal efficiencies of activated sludge diffusion using a typical wastewater treatment plant H2S concentration and investigated the effects that the diffusion of H2S had on the process performance. Results indicated that the levels of H2S produced by other unit processes on a wastewater treatment site (approximately 5 ppm) can be treated using activated sludge diffusion without compromising the performance of the wastewater treatment process. The only effects on the activated sludge plant observed were: (1) nitrification was interrupted briefly as H2S diffusion commenced and (2) the species' diversity in the sludge decreased.

Developments in odour control and waste gas treatment biotechnology: a review.

Waste and wastewater treatment processes produce odours, which can cause a nuisance to adjacent populations and contribute significantly to atmospheric pollution. Sulphurous compounds are responsible for acid rain and mist; many organic compounds of industrial origin contribute to airborne public health concerns, as well as environmental problems. Waste gases from industry have traditionally been treated using physicochemical processes, such as scrubbing, adsorption, condensation, and oxidation, however, biological treatment of waste gases has gained support as an effective and economical option in the past few decades. One emergent technique for biological waste gas treatment is the use of existing activated sludge plants as bioscrubbers, thus treating the foul air generated by other process units of the wastewater treatment system on site, with no requirement for additional units or for interruption of wastewater treatment. Limited data are available regarding the performance of activated sludge diffusion of odorous air in spite of numerous positive reports from full-scale applications in North America. This review argues that the information available is insufficient for precise process design and optimization, and simultaneous activated sludge treatment of wastewater and airborne odours could be adopted worldwide.

Health screening for Gurkha families in UK by chest X-ray, Heaf and blood testing: is it worthwhile?

This paper reports the chest X-rays, Heaf tests and haematology findings on a population of Gurkha wives and their children who arrived in the UK to accompany their husbands on an army base in 1997-8. The conclusions from this study are that there is no benefit from performing chest X-rays, but that screening for rubella and iron deficiency anaemia should continue.

Role of micronutrients in activated sludge-based biotreatment of industrial effluents.

Industrial processes often produce wastewaters that resist biological treatment owing to the unfamiliarity of some components to biological systems. Availability of nutrients determines the community structure of the activated sludge and hence the efficiency of the degradation process. Micronutrients influence the bacteria involved in waste degradation and also the species diversity within the sludge. The requirements for and toxicity of different micronutrients vary according to the nature of the waste and the ecology of the sludge. Adding micronutrients to biological treatment processes is one possible approach to upgrading an existing facility in order to deal with increasing volumes and strengths of industrial wastewaters and the tightening discharge legislation.

Analysis of Y listings and medical discharges of officer Cadets at RMAS from January 1994 to May 1997, with actions to prevent injuries.

During 1995 the incidence of training related injuries to cadets at RMAS increased markedly. This paper quantifies the numbers placed on the Y List and removed from training, and those medically discharged. The main identified causes were drill, weight carriage, endurance training and lack of sleep. The training programme was modified including alterations in footwear, length and timing of physical periods and a reduction in weight carriage. Following these changes there was a highly significant fall in Y Listing from January 1996 and subsequent medical discharge.

Recording compound action potentials from the optic nerve in man and monkeys.

Compound action potentials were recorded from the optic nerve in patients undergoing neurosurgical operations and in rhesus monkeys. The stimuli were short light flashes delivered by light-emitting diodes that were bonded to plastic contact lenses positioned on one or both eyes, and potentials were recorded simultaneously from electrodes placed on the scalp. Potentials recorded from the optic nerve in man have an initial small positive deflection, with a latency of about 45 msec, followed by a negativity with a latency of 60-70 msec. The wave form depends on the recording site on the optic nerve and, occasionally, oscillations with a frequency around 100 Hz were seen in the responses from the optic nerve. There was considerable individual variation in the shape and size of the recorded potentials, but most potentials recorded simultaneously from an electrode placed on Oz with a reference electrode on the forehead appeared as positive deflections with latencies of about 80 msec and, occasionally, with a small positivity with a latency of about 45 msec. Compound action potentials recorded from the optic nerve near the ocular globe in the rhesus monkey in response to similar light flashes appeared as negative deflections with latencies of about 17 msec. The potentials recorded at the chiasm appeared as initial positive deflections, with the latency of the earliest peak being about 35 msec, on which oscillations with frequencies of about 100-150 Hz occasionally could be seen. The recordings from electrodes placed on the scalp (Cz-Oz and Cz-shoulder) in the monkey showed a positive peak with a latency of about 65 msec.(ABSTRACT TRUNCATED AT 250 WORDS)

Neural generators of the somatosensory evoked potentials: recording from the cuneate nucleus in man and monkeys.

The neural generators of the somatosensory evoked potentials (SEPs) elicited by electrical stimulation of the median nerve were studied in man and in rhesus monkeys. Recordings from the cuneate nucleus were compared to the far-field potentials recorded from electrodes placed on the scalp. It was found that the shape of the response from the surface of the human cuneate nucleus to stimulation of the median nerve is similar to that of the response recorded more caudally in the dorsal column, i.e., an initially small positivity followed by a negative wave that is in turn followed by a slow positive wave. The beginning of the negative wave coincides in time with the N14 peak in the SEP recorded from the scalp, and its latency is 13 msec. The response from the cuneate nucleus in the rhesus monkey has a similar shape and its negative peak appears with the same latency as the positive peak in the vertex response that has a latency of 4.5 msec; the peak negativity has a latency of about 6 msec and thus coincides with P6.2 in the vertex recording. Depth recordings from the cuneate nucleus and antidromic stimulation of the dorsal column fibers in the monkey provide evidence that the early components of the response from the surface of the cuneate nucleus are generated by the dorsal column fibers that terminate in the nucleus. The results support the hypothesis that the P14 peak in the human SEP is generated by the termination of the dorsal column fibers and that the cuneate nucleus itself contributes little to the far-field potentials.