Acetic acid recovery from a hybrid biological-hydrothermal treatment process of sewage sludge - a pilot plant study.

A two-stage process consisting of anaerobic fermentation followed by sub-critical wet oxidation was used to generate acetic acid from sewage sludge at pilot scale. Volatile fatty acids, dominated by propionic acid, were produced over 4-6 days in the 2,000 L fermentation reactor, which also achieved 31% solids reduction. Approximately 96% of the carbon was retained in solution over the fermentation stage. Using a 200 L wet oxidation reactor operating in batch mode, the second stage achieved 98% volatile suspended solids (VSS) destruction and 67% total chemical oxygen demand (tCOD) destruction. Acetic acid produced in this stage was recalcitrant to further degradation and was retained in solution. The gross yield from VSS was 16% for acetic acid and 21% for volatile fatty acids across the process, higher than reported yields for wet oxidation alone. The pilot plant results showed that 72% of the incoming phosphorus was retained in the solids, 94% of the nitrogen became concentrated in solution and 41% of the carbon was converted to a soluble state, in a more degradable form. Acetic acid produced from the process has the potential to be used to offset ethanol requirements in biological nutrient removal plants.

Influence of nitrogen limitation on performance of a microbial fuel cell.

We describe the operation of a microbial fuel cell (MFC) system operating on a synthetic wastewater (acetic acid), under conditions of increasing nitrogen limitation. Two MFCs were operated under feed conditions which spanned a range of TKN/COD values of 1.6-28 mg/g. Stable operation was observed in all cases, even when no ammoniacal nitrogen was added to the cell. Improved electrochemical performance (measured as power density, W/m2) was observed as nitrogen limitation was imposed on the cells. Even with no ammonium addition, continuous function of the cell was maintained, at levels consistent with operation at balanced nutrient supplementation. The work has implicated biological nitrogen fixation as a potential source of nitrogen within the MFC. Whilst this hypothesis has yet to be confirmed, the work highlights the opportunity for continuous operation of microbial fuel cells utilising wastewaters with extremely low nitrogen levels, present in pulp and paper, pharmaceutical and petrochemical industries. Further, the described increases in some of the electrochemical indices (e.g. power density) under application of nitrogen limitation may provide a new approach to increasing fuel cell performance. Finally, the lack of any need to add supplemental nitrogen to a MFC-based wastewater treatment technology holds potential for significant financial and environmental savings.

N-ViroTech--a novel process for the treatment of nutrient limited wastewaters.

As pulp and paper wastewaters are mostly deficient in nitrogen and phosphorus, historical practice has dictated that they cannot be effectively treated using microbiological processes without the addition of supplementary nutrients, such as urea and phosphoric acid. Supplementation is a difficult step to manage efficiently, requiring extensive post-treatment monitoring and some degree of overdosing to ensure sufficient nutrient availability under all conditions. As a result, treated wastewaters usually contain excess amounts of both nutrients, leading to potential impacts on the receiving waters such as eutrophication. N-ViroTech is a highly effective alternative treatment technology which overcomes this nutrient deficiency/excess paradox. The process relies on communities of nitrogen-fixing bacteria, which are able to directly fix nitrogen from the atmosphere, thus satisfying their cellular nitrogen requirements. The process relies on manipulation of growth conditions within the biological system to maintain a nitrogen-fixing population whilst achieving target wastewater treatment performance. The technology has significant advantages over conventional activated sludge operation, including: Improved environmental performance. Nutrient loadings in the final treated effluent for selected nitrogen and phosphorus species (particularly ammonium and orthophosphate) may be reduced by over 90% compared to conventional systems; Elimination of nitrogen supplementation, and minimisation of phosphorus supplementation, thus achieving significant chemical savings and resulting in between 25% and 35% savings in operational costs for a typical system; Self-regulation of nutrient requirements, as the bacteria only use as much nitrogen as they require, allowing for substantially less operator intervention and monitoring. This paper will summarise critical performance outcomes of the N-ViroTech process utilising results from laboratory-, pilot-scale and recent alpha-adopter, full-scale trials.

A simple transfixion-ligation treatment of haemorrhoids.

The complications which may occur after existing haemorrhoidectomy procedures are enumerated. A new cost-effective operative procedure which requires minimal facilities and entails anal dilatation with simple transfixion-ligation of all primary and secondary haemorrhoids in one operating session is described. The preoperative and postoperative progress of 56 patients with 2nd to 4th degree haemorrhoids managed by transfixion-ligation of the individual haemorrhoids are presented and evaluated. Postoperative complications were few and mild. Pain and duration of hospitalization were considerably reduced and anal stenosis/fibrosis, faecal/permanent flatus incontinence and recurrence of haemorrhoids were absent. The procedure is recommended for the treatment of all degrees of haemorrhoids especially in developing countries where patients' average income is low, hospitals have few experienced surgical personnel, inadequately equipped operating theatres and an insufficient number of beds.

Cardiotoxic and bronchoconstrictor effects of industrial metal fumes containing barium.

For certain metal arc-welding and other metal processing operations, compounds of barium are used as flux components. Airborne fumes generated by welding with electrodes using barium fluoride or carbonate fluxes may contain 15-30% of barium in readily water-soluble form (Dare et al. 1984). Urine of welders inhaling such fumes was shown to contain elevated levels of barium ions (up to 234 micrograms/l). To assess the possible hazards of such exposure, the toxic potencies of fume samples, expressed in terms of their water-soluble barium ion contents, were compared with effects of solutions of barium salts in anaesthetised guinea-pigs. Dose-effect relationships were established and it was verified that acute toxic effects of inhaled aerosols or of intravenous bolus administration correlated with the barium contents of various forms of welding fumes. Bronchopulmonary reactivity to the barium was observed as marked increases in resistance to ventilatory air-flow, indicating bronchoconstriction. Simultaneously, marked pressor effects on blood pressure occurred. ECG abnormalities indicated myocardial hyperexcitability. Effects were modified by nifedipine and propranolol pretreatments.

A comparative study of the traditional long case with the objective structured clinical examination in Lagos, Nigeria.

An apparent difference in the results of the clinical examination of the final M.B., B.S. was observed following replacement of the traditional long case (TLC) with the Objective Structured Clinical Examination (OSCE) in 1979. This led to a study of the results of two consecutive years of each method, 1976 and 1978 (TLC), and 1979 and 1980 (OSCE). The OSCE pass rate of 61% was found to be significantly lower than TLC pass rate of 93% (P less than 0.05). Using the analysis of variance and the critical difference (CD) of the mean scores of the different types of examination, no significant difference was found to exist between the two TLC examinations or between the two OSCE examinations. However, significant difference exists between the TLC of 1978 and the OSCE of 1979, P less than 0.05. A comparison of the CD of MCQ to those of TLC and OSCE suggests that less differences exist between MCQ and OSCE scores compared to MCQ and TLC scores, and by 1980 no significant difference exists between MCQ and OSCE. OSCE, like MCQ, will therefore appear an acceptable method of examination and perhaps a more effective method of clinical examination than TLC.

Inhalation toxicity studies with 1,3-butadiene -- 1. Atmosphere generation and control.

1,3-butadiene, which is used extensively in the synthetic rubber industry, is a highly reactive, potentially explosive compound, presenting particular problems for the design and execution of inhalation toxicity studies. Before undertaking inhalation studies with butadiene, it was necessary to develop safe systems for the generation and control of stable exposure chamber atmospheres. Infrared and gas chromatographic analytical methods were adapted for monitoring the concentration and distribution of butadiene in exposure chambers, and for analysis of known impurities, particularly, t-butyl catechol and 4-vinyl-1-cyclohexene, in atmospheres generated for inhalation tests.