991 resultados para Ireland--History--1172-1603.
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v.4(1935)
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v.5(1940)
The appraisal of anaerobic digestion in Ireland to develop improved designs and operational practice
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Mesophilic Anaerobic Digestion treating sewage sludge was investigated at five full-scale sewage treatment plants in Ireland. The anaerobic digestion plants are compared and evaluated in terms of design, equipment, operation, monitoring and management. All digesters are cylindrical, gas mixed and heated Continuously Stirred Tank Reactors (CSTR), varying in size from 130m3 to 800m3. Heat exchanger systems heat all digesters. Three plants reported difficulties with the heating systems ranging from blockages to insufficient insulation and design. Exchangers were modified and replaced within one year of operation at two plants. All but one plant had Combined Heat and Power (CHP) systems installed. Parameter monitoring is a problem at all plants mainly due to a lack of staff and knowledge. The plant operators consider pH and temperature the most important parameters to be measured in terms of successful monitoring of an anaerobic digester. The short time taken and the ease at which pH and temperature can be measured may favour these parameters. Three laboratory scale pilot anaerobic digesters were operated using a variety of feeds over at 144-day period. Two of the pilots were unmixed and the third was mechanically mixed. As expected the unmixed reactors removed more COD by retention of solids in the digesters but also produced greater quantities of biogas than the mixed digester, especially when low solids feed such as whey was used. The mixed digester broke down more solids due to the superior contact between the substrate and the biomass. All three reactors showed good performance results for whey and sewage solids. Scum formation occurred giving operational problems for mixed and unmixed reactors when cattle slurry was used as the main feed source. The pilot test was also used to investigate which parameters were the best indicators of process instability. These trials clearly indicated that total Volatile Fatty Acid (VFA) concentrations was the best parameter to show signs of early process imbalance, while methane composition in the biogas was good to indicate possible nutrient deficiencies in the feed and oxygen shocks. pH was found to be a good process parameter only if the wastewater being treated produced low bicarbonate alkalinities during treatment.
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The age, growth, maturity and population dynamics of lemon sole (Microstomus kitt), captured off the west coast of Ireland (ICES division Vllb), were determined for the period November 2000 to February 2002. The maximum age recorded was 14 years. Males of the population were dominated by 4 year olds, while females were dominated by 5 year olds. Females dominated the sex ratio in the overall sample, each month sampled, at each age and from 22cm in total length onwards (when N > 20). Possible reasons for the dominance of females in the sex ratio are discussed. Three models were used to obtain the parameters of the von Bertalanfly growth equation. These were the Ford-Walford plot (Beverton and Holt 1957), the Gulland and Holt plot (1959) and the Rafail (1973) method. Results of the fitted von Bertalanffy growth curves showed that female lemon sole o f f the west coast of Ireland grew faster than males and attained a greater size. Male and female lemon sole mature from 2 years of age onwards. There is evidence in the population o f a smaller asymptotic length (L«, = 34.47cm), faster growth rate (K = 0.1955) and younger age at first maturity, all of which are indicative o f a decrease in population size, when present results are compared to data collected in the same area 22 years earlier. Results of the yield per recruit curve indicate that lemon sole are currently being over-fished o f f the west coast of Ireland. Problems of selectivity within the sampling method, particularly at the discarding stage, may have influenced the outcome of results of the models used in the assessment of this stock. Therefore, additional/future work on this species should include catch data which incorporates discards and not landings data alone.
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1
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The overall purpose of this study was to develop a thorough inspection regime for onsite wastewater treatment systems, which is practical and could be implemented on all site conditions across the country. With approximately 450,000 onsite wastewater treatment systems in Ireland a risk based methodology is required for site selection. This type of approach will identify the areas with the highest potential risk to human health and the environment and these sites should be inspected first. In order to gain the required knowledge to develop an inspection regime in-depth and extensive research was earned out. The following areas of pertinent interest were examined and reviewed, history of domestic wastewater treatment, relevant wastewater legislation and guidance documents and potential detrimental impacts. Analysis of a questionnaire from a prior study, which assessed the resources available and the types of inspections currently undertaken by Local authorities was carried out. In addition to the analysis of the questionnaire results, interviews were carried out with several experts involved in the area of domestic wastewater treatment. The interview focussed on twelve key questions which were directed towards the expert’s opinions on the vital aspects of developing an inspection regime. The background research, combined with the questionnaire analysis and information from the interviews provided a solid foundation for the development of an inspection regime. Chapter 8 outlines the inspection regime which has been developed for this study. The inspection regime includes a desktop study, consultation with the homeowners, visual site inspection, non-invasive site tests, and inspection of the treatment systems. The general opinion from the interviews carried out, was that a standardised approach for the inspections was necessary. For this reason an inspection form was produced which provides a standard systematic approach for inspectors to follow. This form is displayed in Appendix 3. The development of a risk based methodology for site selection was discussed and a procedure similar in approach to the Geological Survey of Irelands Groundwater Protection Schemes was proposed. The EPA is currently developing a risk based methodology, but it is not available to the general public yet. However, the EPA provided a copy of a paper outlining the key aspects of their methodology. The methodology will use risk maps which take account of the following parameters: housing density, areas with inadequate soil conditions, risk of water pollution through surface and subsurface pathways. Sites identified with having the highest potential risk to human health and the environment shall be inspected first. Based on the research carried out a number of recommendations were made which are outlined in Chapter 10. The principle conclusion was that, if these systems fail to operate satisfactorily, home owners need to understand that these systems dispose of the effluent to the 'ground' and the effluent becomes part of the hydrological cycle; therefore, they are a potential hazard to the environment and human health. It is the owners, their families and their neighbours who will be at most immediate risk.
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The current study presents data on age and growth for plaice (Pleuronectes platessa L.) sampled between November 2003 and February 2005 in ICES areas Via (northwest coast of Ireland), Vila (Irish Sea), Vllg (Celtic Sea), VDj (southwest coast of Ireland) and VHb (west coast of Ireland), and data on the reproductive biology and maturity of plaice in ICES area Vllb (west coast of Ireland). This is the first detailed account of the biology of plaice for some of these areas. It is intended that this study will improve understanding of the life cycle of plaice and help fisheries scientists to better predict the effect of fishing effort on Irish plaice stocks. The overall length range found for plaice was 9-51.99cm TL, with a length range of 9-5 lcm TL for females and 9-40cm for males. In all ICES areas the length range for female fish was larger than for male fish. The age range of plaice sampled during this study was 1 to 16 years. In all ICES areas females had a greater range in ages and fish in the larger age groups. From analysis of length and age data it was concluded that there was a significant difference (P=0.000) in growth rate of males and females between ICES areas sampled in March 2004. The highest rate of fishing mortality was determined for ICES area Via (F=1.06) and the lowest for ICES area Vila (F=0.56). In each ICES area male and female plaice have fully recruited to the population by age 4, with the exception of females in ICES area Via, for which a tr value of 5 years was determined. Length at first maturity (L50%) was determined to be 23cm and 21cm for males and females respectively. Age at first maturity (A50%) was determined to be 3 years for both males and females. It was found that males and females in ICES areas Vllb, Vila and Via are well above the length and age at first maturity when they are recruited to the fishery. In ICES area Vllb female plaice spawn from November to March, with peak spawning occurring in February, and male plaice spawn from November to April, with peak spawning occurring in November. Spawning females had an age range of 2 to 10 years and spawning males had an age range of 2 to 7 years. From the oocyte length frequency distributions, it was determined that the plaice is a determinate batch spawner. During this investigation a total of 177 ovaries and 127 testes were staged using both macroscopic and histological criteria. The overall percentage of maturity stages which compared favorably between the two assessment methods was 22.03% for female plaice and 37.80% for male plaice. In general, the findings of this study indicate that there was a very poor match between the macroscopic and histological assessment methods. Given that the histological determination of these stages is based on the observation of a distinct set of developmental features, it is expected that it would be more accurate to use histologically assessed gonads to calculate the annual percentage maturity assessment. The biology of plaice in the areas studied is compared with previous studies of plaice in Irish and European waters.
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vol.A
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5