RESUMEN
Accumulation rates and pathogen concentrations in primary stabilization pond sludges in developing countries are important parameters for adequate sludge management and the safeguarding of public health with sludge reuse in agriculture. An anaerobic pond has been investigated for sludge accumulation rates and helminth egg viability after four years of operation in Burkina Faso. The rate of sludge accumulation was measured at 0.037 m(3)/capita-year or 2.26 kg dry weight/capita-year. An equation describing vertical distribution of total solids in the accumulated sludge was found to be adequately represented by a regression equation. Influent helminth egg concentrations were reduced on average by 90% in the anaerobic pond effluent. Ascaris lumbricoides and Ancylostoma sp. were the most common eggs present in the sludge after four years of operation. The average concentration of helminth eggs in pond sludge was 536 eggs/g TS, and the percentages of viability ranged from 10.8% (47 viable eggs/g TS) to 57.2 (1,772 viable eggs/g TS, with an average rate of 36% (336 viable eggs/g TS). From a sludge depth and section study, egg viability was found to be randomly distributed in the sludge layer.
Asunto(s)
Ancylostoma/metabolismo , Ascaris/fisiología , Aguas del Alcantarillado , Anaerobiosis , Animales , Burkina Faso , Diseño de Equipo , Concentración de Iones de Hidrógeno , Análisis de Regresión , Medición de Riesgo , Temperatura , Factores de Tiempo , Contaminantes del Agua/aislamiento & purificación , Purificación del Agua/métodosRESUMEN
The performance in the removal of estrogenicity from wastewater was studied in three wastewater treatment plants (WWTPs). Different treatment processes were evaluated: stabilization ponds and trickling filter. Sampling was performed from the input to the output of the treatment systems. The total estrogenic activity was determined with MCF-7-derived cell lines which express the endogenous estrogen receptor alpha. The two wastewater stabilization ponds with long retention time had high removal of estrogenicity (90% to 95%). Trickling filters despite being effective at removing organic load were less effective in removing estrogenicity (42%), and post tertiary ponds enhanced estrogenicity removal.
Asunto(s)
Disruptores Endocrinos/análisis , Eliminación de Residuos Líquidos , Purificación del Agua , Línea Celular Tumoral , Disruptores Endocrinos/metabolismo , Receptor alfa de Estrógeno/metabolismo , Cromatografía de Gases y Espectrometría de Masas , HumanosRESUMEN
The Mèze stabilisation pond system has been monitored over more than 20 years. Despite the enlargement of the plant, the organic load doubled between the early 1980s and recent years, the removal of organic matter and nutrients has been maintained at the same level for COD and increased for BOD5, N and P. Combining anaerobic, step-fed aerated and maturation ponds and multiplying the number of cells resulted in a significant improvement in the performances of the plant. Respectively 34, 24 and 23% of the applied COD was eliminated in the anaerobic, the step-fed and the first three maturation ponds, while the figures for BOD5 were 47, 26, and 19% respectively. 38% of the applied nitrogen was eliminated in the first three maturation ponds. Nitrification and denitrification seem to be a major process of nitrogen removal in warm periods. Most of the phosphorus removal was observed to take place in the two polishing ponds.
Asunto(s)
Reactores Biológicos , Nitrógeno/análisis , Compuestos Orgánicos/análisis , Fósforo/análisis , Aguas del Alcantarillado/microbiología , Biodegradación Ambiental , Escherichia coli/aislamiento & purificación , Escherichia coli/metabolismo , Fermentación , Residuos Industriales , Cinética , Nitratos/química , Nitratos/metabolismo , Nitritos/química , Nitritos/metabolismo , Oxígeno/química , Oxígeno/metabolismo , Aguas del Alcantarillado/química , Eliminación de Residuos Líquidos/métodos , Purificación del Agua/métodosRESUMEN
The WSP system serving Mèze and Poussan (French Mediterranean coast) was constructed in 1980 and enlarged and upgraded from 1994 to 1998. Water quality along the waste stabilisation pond to (WSP) system has been monitored over the years, thus allowing us to assess the influence of enlargement and upgrading works. A significant enhancement of the average microbiological quality of the effluent was observed, with respective E. coli and streptococci average abatements of 4.1 and 3.4 log. units. Former seasonal variations of microbiological removal have vanished. The contribution of the different ponds to the disinfection performance of the WSP system was analysed. A microbiological quality model was proposed to evaluate the die-off kinetics related to the different ponds and as a tool for the design and management of WSP systems. Though the relationships between die-off coefficients and environmental factors appeared somewhat frail, this modelling is considered a promising approach for the prediction of WSP microbiological performance.
Asunto(s)
Bacterias/aislamiento & purificación , Heces/microbiología , Aguas del Alcantarillado/microbiología , Microbiología del Agua , Abastecimiento de Agua , Reactores Biológicos , Desinfección , Cinética , Oxígeno/química , Oxígeno/metabolismo , Aguas del Alcantarillado/química , Eliminación de Residuos Líquidos/métodos , Purificación del Agua/métodosRESUMEN
Waste stabilisation pond treatment was widely developed during the 1980s in France, where there are now over 3,000 plants. Desludging the ponds has now become essential. In 19 primary facultative ponds, in operation for 12-24 years, the net average sludge accumulation rate was 19 mm/yr. The average per capita accumulation rates ranged from 0.04-0.148 m3/person.year (mean of 0.08 m3/person.year). In primary facultative ponds the volume of sludge represented 15-39% of the total volume of the basin. A filling rate above 30% necessitates desludging. In France, a desludging interval of 15 years is recommended for primary facultative ponds. The cost evaluation of desludging and landspreading showed differences according to the desludging technique used. Desludging after emptying the water had an average cost of 38 Euro/m3 of sludge with 10% dry solid (range from 20 to 83 Euro/m3). Under-water desludging was 50% more expensive. Although desludging is carried out only after several years of operation, its cost must be allowed for in the annual operation and maintenance costs of the process. It can be estimated to be 3 l/person.year. Even with this additional cost, waste stabilisation pond treatment remains less expensive than other treatment processes.
Asunto(s)
Aguas del Alcantarillado/microbiología , Eliminación de Residuos Líquidos/métodos , Purificación del Agua/métodos , Francia , Aguas del Alcantarillado/química , Factores de Tiempo , Eliminación de Residuos Líquidos/economía , Administración de Residuos , Purificación del Agua/economíaRESUMEN
Anaerobic ponds are highly efficient at removing BOD from wastewater with a reduced land area requirement. However, their use is often limited because of the problem of odor release, primarily due to the emission of hydrogen sulfide (H2S). The experiments were conducted on full scale anaerobic ponds used for the primary treatment of urban wastewater under Mediterranean climatic conditions (south of France). A model was developed to estimate the emission of H2S from water characteristics (temperature, pH and sulfides concentration). The emission rate from anaerobic ponds varied between 20 and 576 mg-S/m2.d, leading to concentrations of H2S in the surrounding atmosphere between 0.2 and 5.2 ppm. These concentrations risked creating odor nuisances for nearby inhabitants. The whole of the results and the analysis of sulfur species in sludge permitted the production of a complete mass balance for sulfur. Methods of reducing the emission of odorous compounds were tested on a large scale. The recirculation of secondary effluent and the use of impermeable or permeable covers appeared to be the most interesting solutions.
Asunto(s)
Contaminantes Atmosféricos/análisis , Bacterias Anaerobias/fisiología , Sulfuro de Hidrógeno/análisis , Modelos Teóricos , Odorantes , Eliminación de Residuos Líquidos/métodos , Reactores Biológicos , Monitoreo del Ambiente , Predicción , Movimientos del AguaRESUMEN
This work concerned the application of anaerobic ponds for the primary treatment of urban wastewater in a Mediterranean climate. It was carried out on anaerobic ponds at large scale in Mèze (France). The anaerobic ponds constitute a good primary treatment with the removal of 55% of SS and 30% of BOD5, with a small surface area. The accumulation rate of sludge was only 0.017 m3/capita.year, due to their intensive anaerobic degradation. The anaerobic digestion reached equilibrium after one year of operation. The accumulation of sludge then showed seasonal variations with a substantial accumulation in winter and the digestion of the stock in summer. This change can be related to the influence of the temperature on methanogenesis. The production of biogas (83% CH4) was measured by gas collectors especially developed for this study and was also strongly dependent on temperature. The mass balance of carbon showed that 74% of the removed organic carbon was converted into CH4, 13% into dissolved inorganic carbon and 15% was stored in sludge. However, the anaerobic ponds presented a risk of creating odor nuisances with the emission of H2S.
Asunto(s)
Contaminantes Atmosféricos/análisis , Bacterias Anaerobias/fisiología , Sulfuro de Hidrógeno/análisis , Metano/análisis , Eliminación de Residuos Líquidos/métodos , Reactores Biológicos , Carbono/metabolismo , Clima , Gases , Región Mediterránea , Aguas del Alcantarillado/químicaRESUMEN
High Rate Algal Ponds (HRAP) were operated at pilot scale to investigate the performance of HRAP under the temperate climate conditions of Shanghai, China. The results indicated that the HRAP gave good efficiency for nutrient removal, especially during summer. With a retention time of 4 or 8d according to the season, the annual average removal efficiencies for COD, NH4-N and PO4-P were 50%, 87% and 40%, respectively. The multi-factor linear models showed the relationships between nutrient removal efficiency and influencing factors. Using a macrophyte pond to separate algae from HRAP can achieve concentrations of COD, TP and TKN in the effluent at around 50 mg/L, 1.5 mg/L and 5 mg/L respectively.
Asunto(s)
Eucariontes , Plantas , Eliminación de Residuos Líquidos/métodos , Purificación del Agua/métodos , Biodegradación Ambiental , China , Filtración , Contaminación del Agua/prevención & controlRESUMEN
This study presents the results of research on a wastewater treatment system with four identical facultative ponds in series with step-feeding and recirculation (SFFPR). Four modes of distribution of the influent were studied, which were (in percentages of the inflow per pond): C1 = 25/25/25/25; C2 = 50/20/20/10; C3 = 50/50/0/0; C4 = 100/0/0/0. The organic loading applied to the four ponds overall was around 200 kg BOD5/ha.d. The distribution C4 = 100/0/0/0 was selected for studying the recycle rate. Three recycling rates were studied: 0.5Q, 1Q and 2Q. COD and BOD5 removal efficiencies were high whatever the step-feed distribution. For the distribution C1 and C2, the four ponds were homogeneous. The equal distribution of organic loading rate in C2 distribution was most beneficial for algal growth. For piston pattern distributions (C3 and C4), the ponds receiving the highest loading showed a bacterial biomass higher than that of the primary production. Increasing the recirculation rate seemed to lead towards homogenisation of the ponds, while a decrease appeared to lead to their individualisation and increased their productivity. The SFFPR constitutes a stage of the treatment process which can replace the facultative stage; it produces a high effluent quality and decreases land area requirements.
Asunto(s)
Eliminación de Residuos Líquidos/métodos , Bacterias , Biodegradación Ambiental , Biomasa , Compuestos Orgánicos/metabolismo , Oxígeno/metabolismo , Dinámica Poblacional , Movimientos del AguaRESUMEN
The preservation of water bodies from eutrophication implies accurate estimation of phosphorus and nitrogen loads and the control of nutrient production on a catchment scale. In this paper, a simple tool for the modelling of annual nutrient loads is presented. It is implemented in ARC/INFO GIS using Arc Macro Language (AML). The use of a GIS is justified as the spatial characteristics of the catchment area (land use, industrial wastewater location) dictate water quality. The annual nutrient loads are worked out on the catchment scale, using existing GIS routines together with specific routines developed in AML for hydrological and water quality modelling purposes. The catchment area is divided into hydrological subcatchments with relatively homogeneous spatial characteristics. Each subcatchment is linked to a specific nutrient export potential. These nutrient loads, calculated on a subcatchment-by-subcatchment basis, are conveyed to the outlet of the catchment and allow annual nutrient load estimation. A comparison with a water monitoring study is conducted to verify the adequation of modelling results for phosphorus and nitrogen loads.
Asunto(s)
Monitoreo del Ambiente/métodos , Eutrofización , Modelos Teóricos , Nitrógeno/análisis , Fósforo/análisis , Agricultura , Recolección de Datos , Ecosistema , Predicción , Geografía , Región Mediterránea , Nitrógeno/efectos adversos , Fósforo/efectos adversos , Contaminación del Agua/prevención & controlRESUMEN
The use of a biological cover for in situ control of gaseous sulfide emission from an anaerobic pond was investigated by a laboratory-scale experiment. The biological cover, constituting by a peat bed floating on the wastewater, caused a reduction of the H2S emission rate by 84.6%. The addition of Fe3+ (with FeCl3) and plants (Juncus effusus L.) to the peat bed significantly improved the performance to reach a H2S removal of 95.5%. Despite the fluctuations in the sulfide concentration in the wastewater, the performance of the biological covers remained constant during the entire period of the study. The analysis of the different forms of sulfur accumulated in the peat beds allowed the understanding of the mechanisms involved in H2S removal. The high amount of sulfate demonstrated that the conditions were favorable to the biological oxidation of H2S. The addition of Fe3+ increased the formation of insoluble ferrous monosulfide (FeS) and pyrite (FeS2). The plants seemed to convert sulfate into elemental and organic sulfur.
Asunto(s)
Sulfuro de Hidrógeno/análisis , Odorantes , Suelo , Contaminación del Aire/prevención & control , Bacterias Anaerobias/fisiología , Biodegradación Ambiental , Oxidación-Reducción , Plantas , Azufre/química , Eliminación de Residuos LíquidosRESUMEN
Nurses use music therapeutically but often assume that all patients will equally appreciate the same type of music. Cultural differences in music preferences are compared across five pain studies. Music preferences for pain relief are described as the most frequently chosen type of music for each culture. Findings indicate that in four studies, musical choices were related to cultural background (p = .002 to .049). Although the majority in each group chose among the other types of music, Caucasians most frequently chose orchestra music, African Americans chose jazz, and Taiwanese chose harp music. For culturally congruent care, nurses should become aware of cultural differences in music preference and provide culturally specific selections among other music expected to have a therapeutic effect.