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D D Mara

Publications and source records attributed to D D Mara.

At least 19 recordsLinked to original sources
PubMed2002

Feasibility of waste stabilization pond technology for small municipalities in Colombia.

The selection of any wastewater treatment technology should take into consideration both "software" and "hardware" aspects. There are contrasting opinions regarding the feasibility of waste stabilisation ponds (WSP): some emphasise their advantages while others are concerned with their high land area requirements. As with any technology, WSP are feasible under specific circumstances related to the context where they are to be implemented. In this study data were collected from three regions in Colombia (Nariño, Tolima and Valle del Cauca) in order to assess the feasibility of WSP under real conditions in a tropical country. A feasibility matrix was developed in order to organise and synthesise the information gathered. The results obtained showed that WSP are highly feasible in Tolima and Valle del Cauca due to the fact that these regions have geographical, socio-economic and technical characteristics that enhance the advantages of WSP technology. Nariño has a very mountainous topography along with other local limitations that hinder the application of WSP technology. The cost of land was not found to be a real limitation for the technology, whereas the availability of land is. Finally, the feasibility matrix may be a good planning tool at regional or national levels in order to help decision-making regarding cost-effective wastewater treatment alternatives on the basis of local conditions.

Colombia↗
PubMed2002

Microbiological quality of a waste stabilization pond effluent used for restricted irrigation in Valle Del Cauca, Colombia.

This paper discusses the applicability of effluent reuse in agriculture after treatment in a series of anaerobic, facultative and maturation ponds. The WSP system is located in Ginebra municipality, a small town in southwest Colombia. The total HRT is 12 days. Several samples of the final effluent were taken over a 55 day period and were analysed for E. coli, Streptococcus spp. and helminth eggs. Some additional grab samples were taken to determine the presence of pathogenic bacteria such as Salmonella spp. and Shigella spp. The results showed that the system was able to remove 4 log units of E. coli, 1 log unit of Streptococcus spp. and 100% of helminth eggs. Meanwhile, Salmonella spp. were detected in the effluent of the facultative pond whilst Shigella spp. were not detected in any sample. The main species of helminth eggs encountered were Taenia spp., Ascaris spp., Trichuris spp., Hymenolepis nana, H. diminuta and Enterobius vermicularis. Removal efficiencies were satisfactory despite the relatively short HRT. Nevertheless, WHO guidelines were slightly surpassed in the case of E. coli for unrestricted irrigation. The helminth egg value was always below the maximum WHO limit. Hence, this effluent can be safely used for restricted irrigation provided that field workers are protected from direct contact with wastewater given the presence of Salmonella spp. in the facultative pond effluent.

Agriculture↗
PubMed2001

Marine-based waste stabilisation ponds: an evaluation of the hydraulic viability.

Marine-Based Waste Stabilisation Ponds, formed by floating boom/skirt curtain enclosures anchored in sheltered waters, have recently been proposed for provision of low-cost effluent treatment facilities where land availability is limited in rapidly expanding coastal cities in the Third World. This paper outlines findings from a viability assessment, which drew on a preliminary site evaluation and baseline environmental survey (for a site in sheltered waters in the Far East), laboratory studies involving scale model tests in wave/wind/current flumes, and a structural and design loading study. It focuses on hydraulic and hydrodynamic considerations and reports the study's conclusions.

Industrial Waste↗
PubMed2001

Wastewater management in Greece: experience and lessons for developing countries.

Technologies to treat wastewater are now well established and are capable of producing almost any degree of purification. The main issue surrounding the selection of a given process lies in deciding which is the most appropriate and applicable technology for the particular social, political and economic environment. This paper concentrates on the development of the municipal wastewater treatment sector in Greece. It examines the deficiencies and problems arising from the implementation of wastewater management policies and makes a number of suggestions and recommendations. The areas considered include, among others, historical development, economic development and pollution control, key issues for wastewater treatment policies and lessons applicable to developing countries. It is hoped that this study will be a valuable source of information for countries embarking on nationwide sanitation projects.

Developing Countries↗
PubMed2000

Guidelines for the microbiological quality of treated wastewater used in agriculture: recommendations for revising WHO guidelines.

Three different approaches for establishing guidelines for the microbiological quality of treated wastewater that is reused for agriculture are reviewed. These approaches have different objectives as their outcomes: the absence of faecal indicator organisms in the wastewater, the absence of a measurable excess of cases of enteric disease in the exposed population and a model-generated estimated risk below a defined acceptable risk. If the second approach (using empirical epidemiological studies supplemented by microbiological studies of the transmission of pathogens) is used in conjunction with the third approach (using a model-based quantitative risk assessment for selected pathogens) a powerful tool is produced that aids the development of regulations. This combined approach is more cost-effective than the first approach and adequately protects public health. The guideline limit for faecal coliform bacteria in unrestricted irrigation (< or = 1000 faecal coliform bacteria/ 100 ml) is valid, but for restricted irrigation < or = 10(5) faecal coliform bacteria/100 ml is recommended when adult farmworkers are exposed to spray irrigation. A limit of < or = 10(3) faecal coliform bacteria/100 ml is recommended if flood irrigation is used or children are exposed. The guideline limit for nematode eggs for both types of irrigation is adequate except when conditions favour the survival of nematode eggs and where children are exposed; in these cases it should be reduced from < or = 1 egg/l to < or = 0.1 egg/l.

Adult↗
PubMed1995

Faecal contamination on children's hands and environmental surfaces in primary schools in Leeds.

Gastro-intestinal diseases continue to be a major health problem in primary schools in the UK. This study, which took place in 20 primary schools in the Leeds area, investigated the presence of faecal indicator bacteria on children's hands and environmental surfaces. Faecal streptococci were used as an indicator of faecal contamination. A handwashing knowledge score was developed for each child. Those children with good hygiene knowledge had less faecal contamination on their hands (relative risk: 1.4, 95% CI = 1.09-1.81, P = 0.005). Those schools with higher hand counts were more likely to have had a reported outbreak of gastroenteritis in the past. Values of the Townsend Deprivation Index, an indicator of deprivation, were compared with the hand results and those schools in high deprivation areas had higher hand counts. Of the swabs taken from surfaces in the toilet areas and classrooms, the carpets in the classrooms were the most frequently contaminated surfaces.

Child, Preschool↗
PubMed1995

An environmental classification of housing-related diseases in developing countries.

A preliminary environmental classification of housing-related diseases in developing countries is presented. This groups these diseases into six categories: those related to defects in (1) buildings and the peridomestic environment, (2) water supply, (3) sanitation, (4) refuse storage and collection and (5) food storage and preparation; and (6) industry-related diseases resulting from housing location (close to polluting industries or on contaminated land) and from the use of the home as a workplace. Each category has three subcategories: communicable diseases (including zoonoses), non-communicable diseases, and mental illnesses and psychosocial disorders.

Developing Countries↗
PubMed1991

Seasonal effects on the reported incidence of acute diarrhoeal disease in northeast Thailand.

This paper examines the seasonal variation in the reported incidence of acute diarrhoea for selected areas in the northeast of Thailand. Charts are presented which show rainfall, temperature and reported incidence of acute diarrhoea for the period 1982 to 1987. Incidence of diarrhoea appears to be inversely related to a sharp decrease in temperature around January each year. Although rainfall does not appear to have a direct effect on the relative incidence of acute diarrhoea, there is always a consistent reduction during July or August, after the rains have begun. Seasonal changes in climate may be indirectly related to other factors which have an important bearing on diarrhoeal disease. Rainwater collection is an important water source in this region and the affect this has on water use is discussed in relation to faeco-oral disease transmission.

Acute Disease↗
PubMed1989

Simple method for the detoxification of wastewater ultrafiltration concentrates for rotavirus assay by indirect immunofluorescence.

A simple method for the detoxification of ultrafiltration concentrates of wastewaters for rotavirus assay by the indirect immunofluorescence technique has been developed. Polyacrylamide (Bio-Gel) or dextran (Sephadex G50) beads were mixed with concentrates (0.5 g/10 ml, wt/vol) of wastewaters seeded with simian rotavirus SA11 and allowed to stand for 2 h. The supernatant was decontaminated with antibiotics and then assayed for rotaviruses. Concentrates from raw sewage and treated effluents seeded with SA11 were used to infect MA104 or LLC MK2 cell lines. The concentrates, particularly those from raw sewage and anaerobic waste stabilization ponds, were very toxic to the tissue culture cells. These toxic effects were determined by the detachment and subsequent loss of cells after incubation with concentrates and assay medium for 24 h. They were either completely eliminated or were reduced by greater than 80% after treatment with beads.

Animals↗
PubMed1988

The faecal coliform fingertip count: a potential method for evaluating the effectiveness of low cost water supply and sanitation initiatives.

A rapid and simple procedure for the enumeration of faecal coliform bacteria present on the fingertips is described. The distribution of individual faecal coliform fingertip counts within households has been compared with a number of variables related to the availability of water supply and sanitation facilities. This showed a strong association between the fingertip count and the possession of in-house water connections. It is proposed that this test might provide a reliable indication of the effectiveness of certain public health interventions.

Bacteriological Techniques↗
PubMed1986

Removal of intestinal nematode eggs in tropical waste stabilization ponds.

The removal of intestinal nematode eggs in waste stabilization ponds treating domestic waste-water was studied in northeast Brazil. Anaerobic and primary facultative ponds achieved Ascaris spp. removals of 88-98% and 99-100%, and hookworm removals of 91-97% and 98-100%, respectively. Egg-free effluents were produced by a single primary facultative pond with a retention time of 18.9 days, and by an anaerobic and a secondary facultative pond in series with retention times of 6.8 and 5.5 days. It is concluded that effluents with less than or equal to 1 egg per litre can be produced by a 1 day anaerobic pond followed by a 5 day secondary facultative and a 5 day maturation pond.

Ascaris↗
PubMed1985

Bacteriological methods for distinguishing between human and animal faecal pollution of water: results of fieldwork in Nigeria and Zimbabwe.

Bacteriological techniques have traditionally been used to detect faecal pollution of drinking water supplies. Recently, methods have been developed to distinguish between human and animal faecal pollution in temperate climates. The present study assessed the applicability and practicality of these methods in tropical countries. Fieldwork in Nigeria and Zimbabwe has shown that animal faecal pollution can reliably be identified by the detection and enumeration of Rhodococcus coprophilus using modified M3 agar, whereas human faecal contamination can be identified by the detection of sorbitol-fermenting bifidobacteria. Each of these organisms was detected only in the faeces of the type (human or animal) that it was meant to indicate. Although Streptococcus bovis has been used in the past in mainly temperate countries to distinguish animal from human faecal contamination, the present study has shown that this organism is not a reliable indicator of animal pollution in the tropics because it was excreted by a proportion of the human population in both Nigeria and Zimbabwe. Water sources known to be contaminated by human or animal excreta were examined for these indicator organisms. The results correlated with the results obtained from examining human and animal faecal specimens for these organisms. The role of these bacteriological methods in water pollution control programmes is discussed.

Animals↗
PubMed1983

Sorbitol-fermenting bifidobacteria as specific indicators of human faecal pollution.

Bifidobacteria were consistently present in the faeces of both man and pigs but only occasionally in the faeces of cattle and sheep, and they were not isolated from faecal samples from other animals; total counts of bifidobacteria were obtained by membrane filtration with YN-17 medium, a modification of Resnick and Levin's YN-6 medium. Mannitol-fermenting strains of bifidobacteria were isolated from both human and animal faeces, but sorbitol-fermenting strains were obtained only from human samples. These sorbitol-fermenting strains were identified as either Bifidobacterium adolescentis or B. breve and their numbers were obtained by membrane filtration of Human Bifid Sorbitol agar (HBSA). Sorbitol-fermenting bifidobacteria are specific indicators of human faecal pollution of waters and wastewaters.

Animals↗
PubMed1983

Investigation of the survival characteristics of Rhodococcus coprophilus and certain fecal indicator bacteria.

Rhodococcus coprophilus and Clostridium perfringens survived in fresh water samples held at 5, 20, and 30 degrees C for over 17 weeks, whereas Escherichia coli and fecal streptococci disappeared after 5 weeks at all three temperatures. R. coprophilus survived for more than 8 months in sterilized sewage and deionized water at all three temperatures, whereas in normal sewage held at 20 degrees C, the survival time was 12 to 26 weeks. In samples held at 30 degrees C, survival times were shorter, probably because of interbacterial competition or protozoal predation. The results indicate that R. coprophilus may be a useful indicator of the presence of remote fecal pollution of farm animal origin, but not of recent pollution, when enumerated alone in polluted waters or wastewaters.

Actinomycetales↗
PubMed1981

Occurrence of Rhodococcus coprophilus and associated actinomycetes in feces, sewage, and freshwater.

Freshwater, sewage, and fecal samples from various sources were examined for Rhodococcus coprophilus, associated actinomycetes, Escherichia coli, and fecal streptococci. Rhodococcus coprophilus was isolated consistently from feces of farm animals, poultry reared in proximity to farm animals, freshwater, and wastewater polluted with animal fecal wastes. It was not isolated from samples of human feces. The ratio of R. coprophilus total actinomycetes was higher in feces from cattle, sheep, ducks, and geese than in specimens from pigs, horses, and fowl. In samples from two freshwater streams polluted by fecal material from farm animals, the ratios of R. copropilus to total actinomycetes were similar to those found in fecal specimens from cattle and sheep. Ratios of fecal coliform to fecal streptococci could not distinguish between fresh human and animal fecal samples and, furthermore, were not reflected in the stream waters polluted by animal fecal material. R. coprophilus has potential in water and dairy bacteriology as a specific indicator organism of fecal pollution due to farm animal wastes.

Actinomycetaceae↗