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C A Buckley

Publications and source records attributed to C A Buckley.

16 recordsLinked to original sources
PubMed2005

A graphical technique for wastewater minimisation in batch processes.

Presented in this paper is a graphical technique for freshwater and wastewater minimisation in completely batch operations. Water minimisation is achieved through the exploitation of inter- and intra-process water reuse and recycle opportunities. In the context of this paper, a completely batch operation is one in which water reuse or recycle can only be effected either at the start or the end of the process. During the course of the operation, water reuse and recycle opportunities are completely nullified. The intrinsic two-dimensionally constrained nature of batch processes is taken into consideration. In the first instance, time dimension is taken as a primary constraint and concentration a secondary constraint. Subsequently, the priority of constraints is reversed so as to demonstrate the effect of the targeting procedure on the final design. Attention is brought to the fact that first and cyclic-state targeting are essential in completely batch operations. Moreover, the exploration and use of inherent storage in batch processes is demonstrated using a real-life case study. Like most graphical techniques, the presented methodology is limited to single contaminants.

Conservation of Natural Resources↗
PubMed2005

Impact of membrane solid-liquid separation on design of biological nutrient removal activated sludge systems.

Installing membranes for solid-liquid separation into biological nutrient removal (BNR) activated sludge (AS) systems makes a profound difference not only in the design of the BNR system itself, but also in the design approach for the whole wastewater treatment plant (WWTP). In multizone BNR systems with membranes in the aerobic reactor and fixed volumes for the anaerobic, anoxic, and aerobic zones (i.e., fixed volume fractions), the mass fractions can be controlled (within a range) with the interreactor recycle ratios. This zone mass fraction flexibility is a significant advantage in membrane BNR systems over conventional BNR systems with SSTs, because it allows for changing of the mass fractions to optimize biological N and P removal in conformity with influent wastewater characteristics and the effluent N and P concentrations required. For PWWF/ADWF ratios in the upper range (f(q) approximately 2.0), aerobic mass fractions in the lower range (f(maer) < 0.60), and high (usually raw) wastewater strengths, the indicated mode of operation of MBR BNR systems is as extended aeration WWTPs. Although the volume reduction compared with equivalent conventional BNR systems with secondary settling tanks is not as large (40% to 60%), the cost of the membranes can be offset against sludge thickening and stabilization costs. Moving from a flow-unbalanced raw wastewater system to a flow-balanced (f(q) = 1), low (usually settled) wastewater strength system can double the ADWF capacity of the biological reactor, but the design approach of the WWTP changes from extended aeration to include primary sludge stabilization. The cost of primary sludge treatment then has to be paid from the savings from the increased WWTP capacity.

Aerobiosis↗
PubMed2002

Metabolic signals, hormones and neuropeptides involved in control of energy balance and reproductive success in hamsters.

In the 'postgenome era', most research on the neuroendocrine control of energy homeostasis has focused on hormonal and neuropeptide control of food intake (i.e. the amount of food eaten) in rats and mice. The amount of food consumed is influenced by both the motivation to procure food and the consummatory act of ingestion. In some species, the rate of food intake remains relatively constant, while survival is maintained via changes in food procurement, external storage and internal expenditure. For example, in hamsters, metabolic signals, peripheral hormones and central neuropeptides influence hunger motivation, food hoarding and changes in energy expenditure without necessarily influencing the amount of food ingested. A similar suite of metabolic signals, hormones and neuropeptides is involved in optimizing reproductive success under fluctuating energetic conditions. Reproductive processes are inhibited or delayed when energy expenditure outstrips energy intake and mobilization from storage. Estrous cyclicity in Syrian hamsters is sensitive to the availability of oxidizable glucose, but the presence of central glucose alone is not sufficient for normal estrous cycles. Food deprivation-induced anestrus does not depend upon food deprivation-induced increases in concentrations of adrenal hormones such as glucocorticoids. If hormones such as insulin and leptin play a role, they might do so by modulating the availability of glucose detected at extra-hypothalamic sites, instead of or in addition to direct effects on the mechanisms that control gonadotropin releasing hormone secretion. Despite our ability to measure and manipulate gene transcription, understanding of fuel homeostasis requires examination of indirect effects of hormones and neuropeptides on peripheral metabolism, attention to the motivational as well as consummatory aspects of ingestion, and the study of behaviour in a natural or seminatural context.

Animals↗
PubMed2002

The application of pinch analysis to water, reagent and effluent management in a chlor-alkali facility.

South African industry is coming under increasing pressure to reduce the amount of freshwater it uses and the amount of effluent it produces. Water pinch is a cleaner production technique aimed at reducing the freshwater consumption and effluent production within a chemical complex. The design of water-reuse or water pinch networks as applied to the case study of a chlor-alkali complex is considered. Insights are provided into the analysis and formulation of problems for large-scale industrial systems and the application of present techniques and tools to the formulated problem is illustrated. The features of the problem posed by the chlor-alkali facility are discussed and the limitations of the present theory in dealing with this problem highlighted. The concepts of utility-waterpinch analysis and process-water pinch analysis are introduced.

Chemical Industry↗
PubMed2002

Life cycle assessment of an industrial water recycling plant.

An industrial water recycling plant was recently commissioned in Durban, South Africa. As with any industrial activity there are environmental burdens associated with water recycling. To assess these burdens a relatively new environmental tool--the life cycle assessment (LCA)--was used. LCA is a systematic way to evaluate the environmental impact of a product or process. This study presents the environmental burdens associated with industrial water and identifies the areas for improvement for the processes involved for recycling water. It was shown that the majority of the environmental burdens for producing industrial water could be traced back to the consumption of electricity for the operation of the plant.

Conservation of Natural Resources↗
PubMed2002

Promoting sustainable industry through waste minimisation clubs.

The concept of waste minimisation clubs was developed in the early 1990s to promote the exchange of experiences between geographically close manufacturers in the implementation of waste minimisation measures. It is a successful approach, resulting not only in a reduction in environmental impact, but also significant financial savings for the companies involved. Two pilot waste minimisation clubs were established in the province of kwaZulu Natal in South Africa in 1998 and 1999, to determine if this approach was a feasible method of promoting sustainable industrial development in South Africa. On conclusion of this project in December 2000, the 20 companies that participated in these clubs had saved a total of US$ 1.7 million, and reduced their water use and effluent discharge by over 2,400 Ml/y.

Conservation of Natural Resources↗
PubMed2002

Toxicity and biodegradability of high strength/toxic organic liquid industrial effluents and hazardous landfill leachates.

Industrial effluents and leachates from hazardous landfill sites were tested for toxicity using the anaerobic toxicity assay. This test was done on several industrial effluents (brewery spent grain effluent, a chemical industry effluent, size effluent), and several hazardous landfill leachates giving vastly different toxicity results. The brewery effluent, spent grain effluent and size effluent were found to be less toxic than the chemical effluent and hazardous landfill leachate samples. The chemical industry effluent was found to be most toxic. Leachate samples from the H:h classified hazardous landfill site were found to be less toxic at high concentrations (40% (v/v)) while the H:H hazardous landfill leachate samples were found to be more toxic even at low concentrations of 4% (v/v). The 30 d biochemical methane potential tests revealed that the brewery effluent, organic spent grain effluent and size effluent were 89%, 63%, and 68% biodegradable, respectively. The leachate from Holfontein hazardous landfill site was least biodegradable (19%) while the chemical effluent and Aloes leachate were 29% and 32% biodegradable under anaerobic conditions.

Bacteria, Anaerobic↗
PubMed2002

Pilot-scale study of an anaerobic baffled reactor for the treatment of domestic wastewater.

Large proportions of South Africans live in areas with inadequate sanitation and a poor infrastructure for waterborne sanitation. Service providers are looking for alternative wastewater treatment options. The anaerobic baffled reactor is being considered as a decentralised sanitation option in these areas. A 3,200 L reactor was built and is currently being evaluated at a wastewater treatment works. The reactor was built based on experiences gained from working with a laboratory reactor (10 L) and predicted flow patterns observed on a computational fluid dynamics model. The design and construction of the reactor will be discussed in this paper. The feed to the reactor consists of screen degritted sewage and the flow to the reactor is maintained by means of a programmable logic controller. The pilot-plant layout is discussed in this paper. Samples are analysed for chemical oxygen demand, pH, alkalinity, ammonia, phosphorus, solids and ash content. Reductions of between 70 and 80% are obtained for COD and the pH values for the effluent samples are within the discharge limits.

Bioreactors↗
PubMed1997

Extended wear disposable soft contact lenses as an alternative to photorefractive keratectomy: report of 4 years experience.

PURPOSE: To establish whether, in a well-informed population, the use of extended wear disposable soft contact lenses (EWDSCL) poses an unacceptable risk to vision and corneal health due to complications associated with their use. METHODS: A 4 year retrospective review of EWDSCL, involving 371 patients in Melbourne from a single general ophthalmology practice. The important aspects of this group were that all patients were given written instructions about the methods of ensuring initial and ongoing cleanliness of lenses, no lenses were cleaned and reinserted, and no solutions other than the saline in the original packaging, and comfort crops, were used. Two types of EWDSCL were used in powers from -9.0 to +6.0 D, and with an initial aim of 4 weeks uninterrupted extended wear. Follow-up was from 2 to 52 months, with an average of 24 months. RESULTS: Of the 354 patients followed up, 236 (66%) regularly wore them on an extended overnight basis, and of these 180 (76%) wore them for the suggested 4 week period before renewal of lenses. In the 471 eyes of 236 patients, adverse reactions occurred at the following rates, marginal infiltrates (12 cases, 2.5%); corneal oedema (10 cases, 2%) peripheral corneal vascularization (2 cases, 0.4%); and presumed infective keratitis (1 case, 0.2%). No eyes lost one or more lines of Snellen acuity. CONCLUSIONS: When disposable soft contact lenses do not come into contact with cleaning solutions, saline from bottles or aerosol cans, or storage cases, their use on an extended wear basis (up to 4 weeks continuous) appears to be associated with a low risk of minor or major complications. The results of this review indicate that controlled usage of EWDSCL is safer than previous reports have indicated.

Adolescent↗
PubMed1994

Intergranular corrosion-fatigue failure of cobalt-alloy femoral stems. A failure analysis of two implants.

Two modular hip implants with a cobalt-alloy head and a cobalt-alloy stem were retrieved after a fracture had occurred in the neck region of the femoral component, eighty-five and seventy months after implantation. Both implants failed less than one millimeter distal to the taper junction between the head and the stem (outside of the taper). The fracture surfaces of the implant were investigated with the use of scanning electron microscopy, to determine the nature of the failure process. The fractures occurred at the grain boundaries of the microstructure and appeared to be the result of three factors: porosity at the grain boundaries; intergranular corrosive attack, initiated both at the head-neck taper and at the free surface; and cyclic fatigue-loading of the stem. The corrosive attack of the free surface was initiated, in part, by the egression of surface grains and by the ingression of fluid into the intergranular regions. Sectioned surfaces showed extensive intergranular corrosive attack in the prosthetic neck localized in the region of the head-neck taper junction and penetrating deeply into the microstructure.

Aged↗
PubMed1993

In vivo corrosion of modular hip prosthesis components in mixed and similar metal combinations. The effect of crevice, stress, motion, and alloy coupling.

One hundred forty-eight retrieved modular hip prostheses of both mixed (Ti-6Al-4V/Co-Cr) and similar (Co-Cr/Co-Cr) metal combinations were examined and positive evidence of corrosive attack was found in the conical taper region between head and stem. Significant corrosion was observed in both mixed and similar metal combinations with 16% of necks and 35% of heads (for mixed-metal cases), and 14% of necks and 23% of heads (for similar-metal cases) showing moderate to severe corrosive attack. There was a significant correlation between the percentage of prostheses with moderate to severe corrosion and the duration of implantation for both mixed and similar metal cases, indicating that this corrosion process is progressive in time. Moderate to severe corrosion was seen as early as 2.5 and 11 months (mixed and similar metals, respectively). Scanning electron microscopy and x-ray analysis identified several forms of corrosive attack in the cobalt-based component of the taper. These included, for both mixed and same metal combinations: preferential dissolution of cobalt, fretting, and pitting; mixed metals only: the formation of a Ti-Cr-Mo interfacial phase and interdendritic corrosion; and for similar metals: intergranular attack adjacent to grain boundaries enriched in molybdenum and silicon. It is hypothesized that the restricted crevice environment, coupled with high cyclic stresses which cause repeated fracture of the passive oxide films in the taper, result in an unstable electrochemical environment within the crevice for both the cobalt alloy and Ti-alloy passive films. The passivity of these alloys is subsequently lost and active attack of the taper results. Also, the repeated fracturing of the passive films will result in large amounts of corrosion products being formed. This corrosion and particulate accumulation could result in loss of mechanical integrity of the implants in vivo, create particles for third body wear, and release particles into the surrounding tissues.

Alloys↗
PubMed1981

The ocular and periocular features of multicentric reticulohistiocytosis with paraproteinaemia. A report of two cases.

Two patients with atypical multicentric reticulohistiocytosis are reported. Skin rigidity with mobile rubbery nodules, and telangiectases, are typical of this disease and occurred around the eyes and elsewhere. One patient also had subconjunctival nodules and corneal crystal formation probably due to her paraproteinaemia. Some literature on this disease and on the occurrence of corneal crystal deposition in dysproteinaemia is reviewed.

Aged↗
PubMed1981

Intraocular melanoma, diabetes, and Turner's syndrome: presentation with proptosis.

A patient with Turner's syndrome and untreated diabetes mellitus presented with a blind, painful, glaucomatous eye and progressive unilateral proptosis. Although a computerised tomographic scan failed to show evidence of a retroocular extension of the presumed choroidal melanoma, the clinical features were so suggestive of extraocular extension that an orbital exenteration was considered. Examination of the enucleated eye for histological conformation of the presence of malignant melanoma showed no extraocular extension, and histology of the retroocular connective tissue revealed only haemorrhage and fibroblastic activity. There are 3 other reported cases of malignant melanoma presenting as proptosis without extraocular extension, so that extreme caution is required when exenteration is deemed necessary on clinical grounds but where computerised scanning fails to reveal direct tumour spread.

Adult↗
PubMed1980

West Indian punctate keratopathy in a Caucasian.

We present a patient with the picture of corneal white spots, very similar in morphology to those described in native West Indians, occurring here in a Caucasian. Their aetiology remains obscure.

Adult↗