Use of micropollutant indicator ratios to characterize wastewater treatment plant efficiency and to identify wastewater impact on groundwater.

Contamination by wastewater has been traditionally assessed by measuring faecal coliforms, such as E. coli and entereococci. However, using micropollutants to track wastewater input is gaining interest. In this study, we identified nine micropollutant indicators that could be used to characterize water quality and wastewater treatment efficiency in pond-based wastewater treatment plants (WWTPs) of varying configuration. Of 232 micropollutants tested, nine micropollutants were detected in treated wastewater at concentrations and frequencies suitable to be considered as indicators for treated wastewater. The nine indicators were then classified as stable (carbamazepine, sucralose, benzotriazole, 4+5-methylbenzotriazole), labile (atorvastatin, naproxen, galaxolide) or intermediate/uncertain (gemfibrozil, tris(chloropropyl)phosphate isomers) based on observed removals in the pond-based WWTPs and correlations between micropollutant and dissolved organic carbon removal. The utility of the selected indicators was evaluated by assessing the wastewater quality in different stages of wastewater treatment in three pond-based WWTPs, as well as selected groundwater bores near one WWTP, where treated wastewater was used to irrigate a nearby golf course. Ratios of labile to stable indicators provided insight into the treatment efficiency of different facultative and maturation ponds and highlighted the seasonal variability in treatment efficiency for some pond-based WWTPs. Additionally, indicator ratios of labile to stable indicators identified potential unintended release of untreated wastewater to groundwater, even with the presence of micropollutants in other groundwater bores related to approved reuse of treated wastewater.

Can quarantine plant-parasitic nematodes within wastes be managed by useful tools in a circular economy approach?

Seen as an integral part of sustainable development, circular economy represents a model of production and consumption notably based on the limitation of both resource wastage and environmental impact. Laboratories and commercial companies working on plant pathogens, in particular quarantine species, must effectively disinfect their waste to avoid disseminating these organisms. The methods used for waste disinfection can however incur high energy costs or pose environmental and human health hazards. Here, we tested the effectiveness of five disinfection methods - chlorination, heat treatment, composting, mesophilic methanation and waste stabilization ponds - on plant-parasitic nematodes belonging to the genera Globodera and Meloidogyne. For the widely used chlorination and heat treatment methods, we showed that they can be very effective in inactivating nematodes at relatively low chlorine doses and temperatures (60 °C-3 min and 50 °C-30 min), respectively. For the three other disinfection methods tested, initially designed for waste recycling, we obtained different levels of efficiency. Composting and mesophilic methanation (based on cattle or pig slurry) both led to the complete elimination of nematodes, even for short treatment durations. However, waste stabilization ponds showed contrasting results, ranging from virtually no effect to high levels of inactivation of nematodes. Our study demonstrates that it is possible to use more environmentally friendly disinfection methods to control plant-parasitic nematodes. In particular, this finding paves the way towards the treatment of infected plant materials using composting or methanation, providing that disinfection is still reached under other (real-life) treatment conditions, especially with other kinds of waste. Both composting and methanation recycle and thus valorize infected waste; they are viable alternatives to landfilling or incineration, thereby demonstrating the usefulness of a circular economy approach.

The contribution of tipping fees to the operation, maintenance, and management of fecal sludge treatment plants: The case of Ghana.

Globally, collection of tipping fees is being promoted as a solution to sustain the operation of fecal sludge treatment plants (FSTPs). Currently, there are six large-scale FSTPs in Ghana, of which five were in operation in June 2017. In Kumasi, Sekondi-Takoradi and Tamale, fecal sludge (FS) is co-treated with landfill leachate using waste stabilization ponds (WSPs). In Tema and Accra, FS is treated using WSPs and a mechanical dewatering system coupled with an upflow anaerobic sludge blanket (UASB). The focus of this study is FSTPs and to assess how, and if, the tipping fees set by the municipalities could enable cost recovery to sustain their long-term operation. Using a questionnaire survey to interview plant managers from the public and private sectors, and directors of waste management departments, we found that the overall average operation, maintenance and management (OM&M) costs per 1000 m3 of treated waste (FS or FS + leachate) in 2017 were USD89 in Kumasi, USD150 in Tamale, USD179 in Tema, USD244 in Sekondi-Takoradi and USD1,743 in Accra. There were important disparities between FSTPs due to their scale, age, and level of treatment and monitoring. Currently, most FSTPs charge tipping fees that range between USD310 and USD530/1000 m3 of FS, averaging USD421 ± 98/1000 m3 of FS discharged at FSTPs. Our study also showed that the OM&M costs of large-scale intensive FSTPs cannot be sustained by relying solely on tipping fees. However, there could be potential to cover the routine expenditures associated with operating smaller FSTPs that relying on WSP technologies.

Integrated approach towards quantifying carbon dioxide and methane release from waste stabilization ponds.

Accurate estimations of gaseous emissions and carbon sequestration in wastewater processing are essential for the design, operation and planning of treatment infrastructure, particularly considering greenhouse gas reduction targets. In this study, we look at the interplay between biological productivity, hydrodynamics and evasion of carbon-based greenhouse gases (GHG) through diffusion and ebullition in order to provide direction for more accurate assessments of their emissions from waste stabilization ponds (WSPs). The ponds stratified in the day and mixed at night. Buoyancy flux contributed between 40 and 75% to turbulence in the water column during nocturnal cooling events, and the associated mixing lead to increasing carbon dioxide (CO2) and methane (CH4) concentrations by up to an order of magnitude in the surface. The onset of stratification and phytoplankton surface blooms, associated with high pH as well as low and variable CO2 partial pressure resulted in an overall reduction of CO2 efflux. Ebullition represented between 40 and 99% of the total CH4 efflux, and up to 95% of the integrated GHG release during wastewater treatment (in CO2 equivalents). Hydrodynamic conditions, diurnal variability and ebullition need to be accounted for reliable assessments of GHG emissions from WSPs. Our study is an important step towards gaining a deeper understanding in the functioning of these hot spots of carbon processing. The contribution of WSPs to atmospheric GHG budget is likely to increase with population growth unless their performance is improved in this regard.

Evaluation of contaminants removal by waste stabilization ponds: A case study of Siloam WSPs in Vhembe District, South Africa.

Waste stabilization ponds (WSPs) are widely used for wastewater management owing to the simplicity of their design, low cost and the use of low-skilled operators. This study was carried out to assess the efficiency of a WSP system in reducing the levels of contaminants in hospital wastewater in a rural area of South Africa and to evaluate the current management of the WSP system. Sampling was conducted monthly from January to June 2014. Physicochemical and microbiological parameters were monitored using standard methods. The microbiological parameters (Escherichia coli and enterococci) in the effluent were higher than those in the influent in some sampling months. Also, low pathogen removal efficiency (<1 log reduction) was recorded. The chemical oxygen demand (COD) in the effluent (82-200 mg/L) exceeded the South African Department of Water Affairs for wastewater discharge guideline value of 75 mg/L although reduction efficiencies of 7.7%, 49.1% and 31.1% were observed for the months of February, April and June, respectively. The WSP system did not show a general trend of contaminant reduction except for Zn (5.5-94.8%). The Siloam WSP is not functioning properly and is releasing effluent of poor quality into the receiving river. It is recommended that the WSP system be expanded to cater for the extra load of wastewater it receives, also desludging should be performed as recommended for such systems. Continuous monitoring of the system for compliance to regulatory guideline should be routinely performed.

Monitoring Microbial Populations and Antibiotic Resistance Gene Enrichment Associated with Arctic Waste Stabilization Ponds.

Wastewater management in the Canadian Arctic is challenging due to climate extremes, small population sizes, and lack of conventional infrastructure for wastewater treatment. Although many northern communities use waste stabilization ponds (WSPs) as their primary form of wastewater treatment, few studies have explored WSP microbial communities and assessed effluent impacts on receiving waters from a microbiological perspective. Here, we used 16S rRNA gene and metagenome sequencing to characterize WSP and receiving water microbial communities for two time points bracketing the spring WSP thaw in Baker Lake (Nunavut) and compared these results to other Nunavut WSPs in Cambridge Bay and Kugluktuk. Most amplicon sequence variants (ASVs) recovered from these WSP samples belonged to the phylum Proteobacteria, with considerable variation between the three locations and only six ASVs shared among the WSPs at >0.2% relative abundance. Wastewater indicator ASVs for the Baker Lake WSP were identified, and few indicator ASVs were detected in samples originating from other upstream or downstream sites. The metagenomic data revealed a strong enrichment of antibiotic resistance genes for WSP samples relative to downstream and reference samples, especially for genes associated with macrolide resistance. Together, our results provide a baseline characterization for WSP microbial communities, demonstrate how indicator ASVs can be used to monitor attenuation and dilution of effluent microorganisms, and reveal that WSPs can serve as hot spots for antibiotic resistance genes.IMPORTANCE Given that the microbial communities of Arctic waste stabilization ponds (WSPs) are poorly studied to date, our characterization of multiple WSP systems and time points provides important baseline data that will assist with ongoing monitoring of effluent impacts on downstream aquatic ecosystems in the Arctic. This research also identifies indicator amplicon sequence variants (ASVs) of WSPs that will be helpful for future monitoring for WSP effluent attenuation and demonstrates that WSP microbial communities are enriched in antibiotic resistance genes. Given operational and infrastructure changes anticipated for wastewater treatment systems in the Arctic, baseline data such as these are essential for further development of safe and effective wastewater treatment systems.

Integration of water hyacinth plants into waste stabilization ponds: a case study of Donnybrook 4 Sewage Ponds in Mabvuku-Tafara, Harare, Zimbabwe.

Donnybrook Waste Stabilization Ponds (WSP) are overloaded and water hyacinth plants have infested the ponds. The study assessed the feasibility of integrating the problematic water hyacinth plants into the current treatment process. Grab samples of influent and effluent for each pond were collected between 28 March and 23 April 2019 and the analysis was done following standard APHA methods. Parameters considered include pH, turbidity, TDS, TSS, TN, TP, BOD, and COD. The raw sewage mean pH, turbidity, TDS, TSS, TN, TP, BOD, and COD were 8.08, 580 NTU, 1639 mg/L, 1294 mg/L, 78 mg/L, 8.16 mg/L, 287 mg/L, and 887 mg/L. The mean pH, turbidity, TDS, TSS, TN, TP, BOD, and COD in the effluent from the existing maturation pond, control pilot pond, and water hyacinth pilot pond were 7.7, 7.7, and 7.3; 75, 67, and 47 NTU; 861, 758, and 668 mg/L; 276, 172, and 82 mg/L; 27, 28, and 17 mg/L; 4, 5.28, and 4 mg/L; 114, 52, and 30 mg/L; and 243, 122, and 81 mg/L. It was concluded that the water hyacinth may be integrated into the WSP system to enhance contaminant removal. The water hyacinth in the ponds should be harvested periodically to avoid secondary organic and nutrient loading from dead plants.

Microalgae and bacteria dynamics in high rate algal ponds based on modelling results: Long-term application of BIO_ALGAE model.

The mechanistic model (BIO_ALGAE) for microalgae-bacteria based wastewater treatment systems simulation was validated in the long-term (months) using experimental results from a pilot high rate algal pond (HRAP) treating municipal wastewater. Simulated results were compared with data gathered during two different seasons (summer and winter), and with the HRAP operating at different hydraulic retention times (HRT, 4 and 8 days, respectively). The model was able to simulate with a good degree of accuracy the dynamics of different components in the pond, including the total biomass (bacteria and microalgae). By means of practical study cases, the influences of different HRT operating strategies and seasonal variations of temperature and irradiance were investigated for the relative proportion of microalgae and bacteria, and biomass production over a year cycle. Model predictions show that the proportion of microalgae in the microalgal/bacterial biomass is quite similar in warmer months if the pond is operated with 8-day HRT (76-78%) or 4-day HRT (60-75%). Significant differences were observed in colder months (4-day HRT (27-33%) and 8-day HRT (65-68%)). The model identified a scenario in which overall microalgae production and ammonium removal efficiency were optimized. By operating the HRAP with lower HRT (4 days) in warmer months and higher HRT (8 days) in colder months, the average annual microalgae production increased up to 14.1 gTSS m-2d-1, in contrast with 10.2 gTSS m-2d-1 and 9.2 gTSS m-2d-1 operating with constant HRAP (4 and 8 days, respectively) over a year cycle.

Sulfur oxidation by Achromobacter xylosoxidans strain wsp05 reveals ecological widening over which thiotrophs are distributed.

Achromobacter xylosoxidans is a versatile bacterium known for its ability to degrade aromatic compounds. However, its ability to oxidize sulfur compounds for electron and energy source is not reported much. In the present work, the Gram-negative bacterium Achromobacter xylosoxidans strain wsp05 isolated from a waste stabilization ponds (WSPs) system was studied for its ability to oxidize reduced sulfur compounds. The strain was able to oxidize thiosulfate and sodium sulfite. To observe the effect of physicochemical parameters on the rate of sulfur oxidation, strain wsp05 was grown in thiosulfate (20 mM) containing minimal salt medium at varied pH, temperature and ammonium and phosphate ions concentration. Maximum thiosulfate oxidation was observed at 30 °C with initial pH of 7-7.2. The strain was characterized using universal 16S rRNA gene primers revealing high similarity (> 99%) with Achromobacter xylosoxidans NBRC 15126T belonging to ß-proteobacteria. In the present study, we investigated the sulfur oxidation properties of the Achromobacter xylosoxidans strain wsp05, which revealed an ecological and phylogenetic widening over which the thiotrophs are distributed.

Design of waste stabilization pond systems: A review.

A better design instruction for waste stabilization ponds is needed due to their growing application for wastewater purification, increasingly strict environmental regulations, and the fact that most of previous design manuals are outdated. To critically review model-based designs of typical pond treatment systems, this paper analyzed more than 150 articles, books, and reports from 1956 to 2016. The models developed in these publications ranged from simple rules and equations to more complex first-order and mechanistic models. From a case study on all four approaches, it appeared that rules of thumb is no longer a proper tool for pond designs due to its low design specification and very high output variability and uncertainty. On the other hand, at the beginning phase of design process or in case of low pressure over land and moderate water quality required, regression equations can be useful to form an idea for pond dimensions. More importantly, mechanistic models proved their capacity of generating more precise and comprehensive designs but still need to overcome their lack of calibration and validation, and overparameterization. In another case study, an essential but often overlooked role of uncertainty analysis in pond designs was investigated via a comparison between deterministic and uncertainty-based approaches. Unlike applying a safety factor representing all uncertainty sources, probabilistic designs quantify the uncertainty of model outputs by including prior uncertainty of inputs and parameters, which generates more scientifically reliable outcomes for decision makers. Based on these findings, we advise engineers and designers to shift from the conventional approaches to more innovative and economic tools which are suitable for dealing with large variations of natural biological systems.

Microalgae-bacteria models evolution: From microalgae steady-state to integrated microalgae-bacteria wastewater treatment models - A comparative review.

The search for environmentally neutral alternative fuels had revived the interest for microalgae-bacteria wastewater treatment systems. The potential achieving of bioproducts from microalgae biomass has also greatly contributed. The reactions that occur in these systems are complex, and the degree of scientific knowledge is still scarce compared to that of conventional bacteria wastewater treatments. Mathematical models offer a great opportunity to study the simultaneous effect of the multiple factors affecting microalgae and bacteria, thus allowing for the prediction of final biomass production, and contributing to the system design optimization in terms of operation and control. During the last decades, numerous models describing microalgae growth have been proposed. However, a lower number of integral models considering microalgae as well as bacteria is available. In this paper, the evolution of microalgae models from simple steady-state models (usually dependent on one factor) to more complex dynamic models (with two or more factors) has been revised. A summary of integrated microalgae-bacteria models has been reviewed, outlining their main features and presenting their processes and value parameters. Eventually, a critical discussion on integrated models has been put forward.

Antibiotic resistance genes in municipal wastewater treatment systems and receiving waters in Arctic Canada.

Domestic wastewater discharges may adversely impact arctic ecosystems and local indigenous people, who rely on being able to hunt and harvest food from their local environment. Therefore, there is a need to develop efficient wastewater treatment plants (WWTPs), which can be operated in remote communities under extreme climatic conditions. WWTPs have been identified as reservoirs of antibiotic resistance genes (ARGs). The objective of this work was to quantify the presence of nine different ARG markers (int1, sul1, sul2, tet(O), erm(B), mecA, blaCTX-M, blaTEM, and qnr(S)) in two passive systems (waste stabilization ponds [WSPs]) and one mechanical filtration plant operating in two smaller and one large community, respectively, in Nunavut, Canada. Measurement of water quality parameters (carbonaceous oxygen demand, ammonia, total suspended solids, Escherichia coli and total coliforms) showed that the WWTPs provided only primary treatment. Low levels of the ARGs (2logcopies/mL) were observed in the effluent, demonstrating that bacteria residing in three northern WWTPs harbour ARGs conferring resistance to multiple clinically-relevant classes of antibiotics. Our results indicate that long-term storage in WSPs benefitted removal of organic material and some ARGs. However, one WSP system showed evidence of the enrichment of sul1, sul2, mecA, tet(O) and qnr(S). Further research is needed to fully understand if these ARG releases pose a risk to human health, especially in the context of traditional hunting and fishing activities.

Sludge accumulation and distribution impact the hydraulic performance in waste stabilisation ponds.

Waste stabilisation ponds (WSPs) are used worldwide for wastewater treatment, and throughout their operation require periodic sludge surveys. Sludge accumulation in WSPs can impact performance by reducing the effective volume of the pond, and altering the pond hydraulics and wastewater treatment efficiency. Traditionally, sludge heights, and thus sludge volume, have been measured using low-resolution and labour intensive methods such as 'sludge judge' and the 'white towel test'. A sonar device, a readily available technology, fitted to a remotely operated vehicle (ROV) was shown to improve the spatial resolution and accuracy of sludge height measurements, as well as reduce labour and safety requirements. Coupled with a dedicated software package, the profiling of several WSPs has shown that the ROV with autonomous sonar device is capable of providing sludge bathymetry with greatly increased spatial resolution in a greatly reduced profiling time, leading to a better understanding of the role played by sludge accumulation in hydraulic performance of WSPs. The high-resolution bathymetry collected was used to support a much more detailed hydrodynamic assessment of systems with low, medium and high accumulations of sludge. The results of the modelling show that hydraulic performance is not only influenced by the sludge accumulation, but also that the spatial distribution of sludge plays a critical role in reducing the treatment capacity of these systems. In a range of ponds modelled, the reduction in residence time ranged from 33% in a pond with a uniform sludge distribution to a reduction of up to 60% in a pond with highly channelized flow. The combination of high-resolution measurement of sludge accumulation and hydrodynamic modelling will help in the development of frameworks for wastewater sludge management, including the development of more reliable computer models, and could potentially have wider application in the monitoring of other small to medium water bodies, such as channels, recreational water bodies, and commercial ports.

Analysis of intensity and spatial patterns of public use in natural treatment systems using geotagged photos from social media.

Patterns of public use in 273 natural treatment systems worldwide are investigated by means of geotagged data from two popular photo-sharing websites, using spatial analysis and regression techniques. Standardized Major Axis (SMA) regression is found to perform better than other univariate calibration models in terms of goodness of fit with reported visitation frequencies and predictive accuracy, and is used to predict visitation rates in 139 systems that are associated with at least one geotagged photograph. High visitation rates are found in free-water surface (FWS) constructed wetlands and mixed pond-constructed wetlands systems, as well as systems treating surface water or stormwater runoff. Geographic Information System (GIS) techniques are used to map hot and cold spots of public use in two highly visited systems. Binomial logit regression reveals that the probability to be associated with at least one geotagged photograph is a function of system size, system type, and influent water quality. The findings are discussed in terms of their implications for the evaluation of public use in multifunctional ecologically engineered systems as well as the applicability of the proposed methodology to other natural and man-made ecosystems.

Occurrence of Clostridium difficile in two types of wastewater treatment plants.

Wastewater is a potential environmental source of Clostridium difficile, although a direct link with community-acquired C. difficile infection (CA-CDI) in humans has not yet been established. The present study was performed to determine the occurrence of C. difficile in two types of wastewater treatment plants (WWTPs) in Isfahan, Iran. A total of 95 samples were taken from a conventional activated sludge treatment plant and a waste stabilization ponds system, and analyzed for the presence of C. difficile. C. difficile was found in 13.6% (3/22) of digested sludge samples. However, no C. difficile was detected in inlet and outlet samples or in raw sludge of activated sludge. C. difficile was also detected in 5% (2/40) of the samples from waste stabilization ponds. Polymerase chain reaction (PCR) analysis showed that all strains of C. difficile detected were toxigenic (tcdB gene positive). This study shows that C. difficile was present in WWTPs, which might constitute a potential source of community-acquired C. difficile infection.

Performance assessment of aquatic macrophytes for treatment of municipal wastewater.

The objective of the study was to evaluate the performance of three different aquatic macrophytes for treatment of municipal wastewater collected from Taxila (Pakistan). A physical model of treatment plant was constructed and was operated for six experimental runs with each species of macrophyte. Every experimental run consist of thirty days period. Regular monitoring of influent and effluent concentrations were made during each experimental run. For the treatment locally available macrophyte species i.e. water hyacinth, duckweed & water lettuce were selected to use. To evaluate the treatment performance of each macrophyte, BOD5, COD, and Nutrients (Nitrogen and Phosphorus) were monitored in effluent from model at different detention time of every experimental run after ensuring steady state conditions. The average reduction of effluent value of each parameter using water hyacinth were 50.61% for BOD5, 46.38% for COD, 40.34% for Nitrogen and 18.76% for Phosphorus. For duckweed the average removal efficiency for selected parameters were 33.43% for BOD5, 26.37% for COD, 17.59% for Nitrogen and 15.25% for Phosphorus and for Water Lettuce the average removal efficiency were 33.43% for BOD5, 26.37% for COD, 17.59% for Nitrogen and 15.25% for Phosphorus. The mechanisms of pollutant removal in this system include both aerobic and anaerobic microbiological conversions, sorption, sedimentation, volatilization and chemical transformations. The rapid growth of the biomass was measured within first ten days detention time. It was also observed that performance of macrophytes is influenced by variation of pH and Temperature. A pH of 6-9 and Temperature of 15-38°C is most favorable for treatment of wastewater by macrophytes. The option of macrophytes for treatment of Municipal sewage under local environmental conditions can be explored by further verifying the removal efficiency under variation of different environmental conditions. Also this is need of time that macrophyte system should be used for treatment of wastewater because their performance is comparable to conventional wastewater treatment plants and also the system has very low O&M costs.

Performance comparison and economics analysis of waste stabilization ponds and horizontal subsurface flow constructed wetlands treating domestic wastewater: a case study of the Juja sewage treatment works.

The performance, effluent quality, land area requirement, investment and operation costs of a full-scale waste stabilization pond (WSP) and a pilot scale horizontal subsurface flow constructed wetland (HSSF-CW) at Jomo Kenyatta University of Agriculture and Technology (JKUAT) were investigated between November 2010 to January 2011. Both systems gave comparable medium to high levels of organic matter and suspended solids removal. However, the WSP showed a better removal for Total Phosphorus (TP) and Ammonium (NH4(+)-N). Based on the population equivalent calculations, the land area requirement per person equivalent of the WSP system was 3 times the area that would be required for the HSSF-CW to treat the same amount of wastewater. The total annual cost estimates consisting of capital, operation and maintenance (O&M) costs were comparable for both systems. However, the evaluation of the capital cost of either system showed that it is largely influenced by the size of the population served, local cost of land and the construction materials involved. Hence, one can select either system in terms of treatment efficiency. When land is available other factor including the volume of wastewater or the investment, and O&M costs determine the technology selection.

Desempeño de una laguna anaerobia con bafle divisor seguida de una laguna facultativa, posible afectación de la salud pública

Esta investigación tuvo como objetivo principal evaluar la eficiencia de la estación para tratamiento de aguas residuales de la ciudad Santa Fé do Sul (São Paulo) y definir posibles efectos en la salud pública producidos por la calidad del efluente final. Se realizó un estudio batimétrico de las lagunas de estabilización anaerobia con bafle divisor y facultativa para formar un perfil de acumulación de lodos; se monitoreó durante 24 horas consecutivas el afluente bruto y los efluentes de las lagunas para diagnosticar el comportamiento de la Estación. La eficiencia media de remoción de la demanda bioquímica de oxígeno fue del 89%, mayor que la mínima eficiencia exigida por la legislación brasilera vigente. La cantidad de coliformes fecales superó en gran medida los valores permitidos; sin embargo, la concentración de sólidos sedimentables cumplió a cabalidad con la norma ambiental presentando valores menores a 1,0 mL/L. Los resultados mostraron que la estación requiere labores de mantenimiento de la laguna anaerobia, así como mayor control operacional y mantenimiento más efectivos. Se evidenció la necesidad de implementar un sistema de pos tratamiento que garantice la reducción de los coliformes fecales del efluente final como medida para disminuir posibles riesgos a la salud pública en la zona de descarga y aguas abajo del punto de vertimiento final.

The main objective in this research was to evaluate the efficiency of the sewage treatment plant of Santa Fé do Sul city (São Paulo) and to define possible effects on public health produced by the final effluent quality. A bathymetric study of the anaerobic with baffle and facultative stabilization ponds was done in order to define the sludge accumulation profile; the raw influents and the lagoons effluents were monitored during 24 consecutive hours to diagnose the Plant performance. The average efficiency of the biochemical oxygen demand was 89%, higher than the minimum efficiency allowed by the Brazilian current legislation. The amount of fecal coliforms highly exceeds the permitted values; however the settleable solids concentration achieved the environmental regulation with values lower than 1, 0 mL/L. The results indicated that the station requires maintenance works at the anaerobic pond, a better operational control and more effective maintenance. It was shown the need to install a post treatment system to guarantee the reduction of the fecal coliforms at the final effluent as an action to diminish the public health possible risks in the discharge zone and downstream of the final dump point.

Avaliação de métodos espectrofotométricos para determinação de proteína em amostras de lagoas de estabilização / Evaluation of spectrophotometric methods for protein determination in waste stabilization ponds sample

Esta pesquisa teve como objetivo principal comparar cinco métodos espectrofotométricos para determinação de proteínas em amostras provenientes de estações de tratamento de efluentes sanitários. O intuito foi definir uma metodologia de aplicação rápida, fácil e confiável para este tipo de amostra. As lagoas de estabilização, como sistemas de tratamento biológico, têm como principais constituintes proteínas, carboidratos e lipídeos, mas também apresentam muitos compostos interferentes, como por exemplo, uréia, detergentes e compostos fenólicos, que podem prejudicar a quantificação de tais parâmetros. Os métodos analisados foram Lowry, Biureto, Bradford e Ácido bicinconínico. O método de Lowry mostrou-se mais adequado às características da amostra, com boa reprodutibilidade, reagente específico, custo moderado e ausência de substancias interferentes.

This research had as main objective to compare five spectrophotometric methods for protein determination in samples proceeding from sanitary effluent of treatment plant. Intention was to define a methodology that is of fast and easy and reliable application for this type of sample. The stabilization ponds, as systems of biological treatment, have as main constituent proteins, carbohydrates and lipids, but also they present many interfering composites, for example, phenolic urea, detergents and composites, that can harm the quantification of such parameters. The analyzed methods had been Lowry, Biuret, Bradford and Acid bicinconinic. The method of Lowry revealed more adequate to the characteristics of the sample, with good reproducibility, specific reagent, moderate cost and absence of interfering substance.

Dinâmica de nitrogênio em um sistema de lagoas de estabilização na região do Vale do Ribeira (São Paulo - Brasil) / Nitrogen dynamic in waste stabilization ponds systems in the Ribeira's Valley region (São Paulo - Brasil)

Esta pesquisa teve como principal objetivo investigar os pro-cessos envolvidos nas transformações do nitrogênio em um sistema de lagoas de estabilização. Em amostragem nictemeral (24 horas) observou-se forte estratificação térmica durante a maior parte do ciclo amostrado a qual condicionou a compartimentalização vertical e a estratificação química nas duas lagoas, possibilitando a análise dos processos de forma segmentada pela ACP (análise de componentes principais), que mostrou-se ferramenta estatística muito útil na caracterização dos processos. A degradação de proteína, com subseqüente geração e acúmulo de nitrogênio amoniacal, foi observada, além da possível excreção de proteína ou aminoácidos por organismos fitoplanctônicos na superfície das lagoas. A provável ocorrência de nitrificação na superfície da lagoa anaeróbia evidenciou a necessidade de otimização de operação do sistema a fim de viabilizar a remoção de nitrogênio através da desnitrificação, processo provavelmente inibido pelas elevadas concentrações de oxigênio dissolvido registradas durante o dia.

This research had as main objective to investigate the involved processes in the transformations of nitrogen in a system of waste stabilization ponds. In nictemeral sampling (24 hours) strong thermal stratification was observed during most of the showed cycle which conditioned two vertical compartments and the chemical stratification in the two lagoons, making possible the analysis of the processes of segmented form for PCA (Principal Components Analysis) that was a very useful statistics tool in the characterization of the processes. The protein degradation was observed with subsequent generation and accumulation of ammoniacal nitrogen, beyond the possible excretion of protein or amino acids for phytoplanktonic organisms in the surface of the ponds. The probable occurrence of nitrification in the surface layer of the anaerobic pond evidenced the necessity of improving the operation parameters of the system in order to reach a greater nitrogen removal through the denitrification, process probably inhibited by significant high concentrations of oxygen dissolved registered in superficial layers, particularly during the day.