Conventional Sewage Treatment Plant Research Articles

Modeling the Fate of Priority Pharmaceuticals in Korea in a Conventional Sewage Treatment Plant

Understanding the environmental fate of human and animal pharmaceuticals and their risk assessment are of great importance due to their growing environmental concerns. Although there are many potential pathways for them to reach the environment, effluents from sewage treatment plants (STPs) are recognized as major point sources. In this study, the removal efficiencies of the 43 selected priority pharmaceuticals in a conventional STP were evaluated using two simple models: an equilibrium partitioning model (EPM) and STPWIN TM program developed by US EPA. It was expected that many pharmaceuticals are not likely to be removed by conventional activated sludge processes because of their relatively low sorption potential to suspended sludge and low biodegradability. Only a few pharmaceuticals were predicted to be easily removed by sorption or biodegradation, and hence a conventional STP may not protect the environment from the release of unwanted pharmaceuticals. However, the prediction made in this study strongly relies on sorption coefficient to suspended sludge and biodegradation half-lives, which may vary significantly depending on models. Removal efficiencies predicted using the EPM were typically higher than those predicted by STPWIN for many hydrophilic pharmaceuticals due to the difference in prediction method for sorption coefficients. Comparison with experimental organic carbon-water partition coefficients (Kocs) revealed that log KOW-based estimation used in STPWIN is likely to underestimate sorption coefficients, thus resulting low removal efficiency by sorption. Predicted values by the EPM were consistent with limited experimental data although this model does not include biodegradation processes, implying that this simple model can be very useful with reliable Koc values. Because there are not many experimental data available for priority pharmaceuticals to evaluate the model performance, it should be important to obtain reliable experimental data including sorption coefficients and biodegradation rate constants for the prediction of the fate of the selected pharmaceuticals.

Monitoring the biological activity of micropollutants during advanced wastewater treatment with ozonation and activated carbon filtration

A bioanalytical test battery was used to monitor the removal efficiency of organic micropollutants during advanced wastewater treatment in the South Caboolture Water Reclamation Plant, Queensland, Australia. This plant treats effluent from a conventional sewage treatment plant for industrial water reuse. The aqueous samples were enriched using solid-phase extraction to separate some organic micropollutants of interest from metals, nutrients and matrix components. The bioassays were chosen to provide information on groups of chemicals with a common mode of toxic action. Therefore they can be considered as sum indicators to detect certain relevant groups of chemicals, not as the most ecologically or human health relevant endpoints. The baseline toxicity was quantified with the bioluminescence inhibition test using the marine bacterium Vibrio fischeri. The specific modes of toxic action that were targeted with five additional bioassays included aspects of estrogenicity, dioxin-like activity, genotoxicity, neurotoxicity, and phytotoxicity. While the accompanying publication discusses the treatment steps in more detail by drawing from the results of chemical analysis as well as the bioanalytical results, here we focus on the applicability and limitations of using bioassays for the purpose of determining the treatment efficacy of advanced water treatment and for water quality assessment in general. Results are reported in toxic equivalent concentrations (TEQ), that is, the concentration of a reference compound required to elicit the same response as the unknown and unidentified mixture of micropollutants actually present. TEQ proved to be useful and easily communicable despite some limitations and uncertainties in their derivation based on the mixture toxicity theory. The results obtained were reproducible, robust and sensitive. The TEQ in the influent ranged in the same order of magnitude as typically seen in effluents of conventional sewage treatment plants. In the initial steps of the treatment chain, no significant degradation of micropollutants was observed, and the high levels of dissolved organic carbon probably affected the outcome of the bioassays. The steps of coagulation/flocculation/dissolved air flotation/sand filtration and ozonation decreased the effect-based micropollutant burden significantly.

Discharge of pharmaceutical products (PPs) through a conventional biological sewage treatment plant: MECs vs PECs?

Pharmaceuticals for human use are consumed in significant quantities and their occurrence in aquatic systems has been reported by a number of authors. In the context of environmental risk assessment, there is an increasing interest in evaluating the discharge of pharmaceutical products to surface waters through sewage treatment plants (STP). This case study was carried out on a conventional biological treatment plant (Alès, France) and focused on a set of eleven drugs representing the main therapeutic classes. Measured environmental concentrations (MECs) range from the low ng L − 1 to 1.5 µg L − 1 in effluent and up to few hundred ng L − 1 in receiving surface waters. There is a good agreement between MEC and predicted environmental concentration (PEC) values for seven of the eleven investigated drugs in STP effluent. There is not such a good match between PEC and MEC values in surface waters, and this highlights the limits of this approach, at the local scale.

Characterization of isolated fractions of dissolved organic matter from sewage treatment plant and the related disinfection by-products formation potential

Dissolved organic matter (DOM) in effluent from a conventional sewage treatment plant was isolated using resin adsorbents into six classes: hydrophobic bases (HoB), hydrophobic acids (HoA) and hydrophobic neutrals (HoN); hydrophilic bases (HiB), hydrophilic acids (HiA) and hydrophilic neutrals (HiN). Organic acids were the most abundant fractions of DOM. Hydrophobic organics especially hydrophobic acids were found to have higher overall disinfection by-products formation potential (DBPFP). Moreover, the potential decreased as the sequence of acids, neutrals and bases. Ultraviolet spectrophotometry at 254 nm (UV 254), fluorescence spectroscopy, size exclusion chromatography and Fourier transform infrared spectroscopy (FTIR) were employed to characterize DOM fractions. And the relationship between the characteristics of DOM fractions and the related DBPFP was discussed in detail. It was found that UV 254 to DOC ratio (SUVA) exhibited a positive correlation with haloacetic acids (HAAs) formation potential whereas distinctive linear correlation was not observed between SUVA and trihalomethanes (THMs) formation potential. Of the fluorescence organics contained in DOM, humic acids exhibited higher chlorine reactivity than fulvic acids. Smaller molecules of humic acids produced more DBPs. Furthermore, a combination of aromatic moieties and aliphatic structures with ν(C O) groups contributed largely to the formation of DBPs.

Isolation of dissolved organic matter in effluents from sewage treatment plant and evaluation of the influences on its DBPs formation

Dissolved organic matter (DOM) in reclaimed water from a conventional sewage treatment plant was isolated using resin adsorption chromatography technique into six classes: hydrophobic bases (HoB), hydrophobic acids (HoA), hydrophobic neutrals (HoN), hydrophilic bases (HiB), hydrophilic acids (HiA) and hydrophilic neutrals (HiN). It was found that organic acids dominated in reclaimed water and the ratios of UV 254 (absorbance at 254 nm) to dissolved organic carbon (DOC) (SUVA 254) ratio exhibited a common relationship: HoA > reclaimed water > HiA. The influences of chemical structures and experimental conditions on the formation of disinfection by-products (DBPs) were investigated, respectively. SUVA 254 was found to exhibit a positive and statistically significant correlation with DBPs formation potential. The specific trihalomethanes (THMs) and haloacetic acids (HAAs) formation potential decreased as the same sequence: acids, neutrals and bases. The formation of DBPs depended more on a combination of aromatic moieties and aliphatic structures such as hydroxy acids. Furthermore, THMs formed more easily at alkaline conditions; however, hydrophobic organics formed HAAs more easily at acidic conditions, whereas hydrophilic organics achieved relatively high HAAs at both acidic and strong alkaline conditions. Moreover, the observed rate constant for HAAs formation was larger than the rate constant for THMs formation. Addition of ammonia nitrogen (NH 4-N) changed chlorine to chloramines with lower oxidation potential, and correspondingly influenced the formation of DBPs especially at the chlorination breakpoint.

Bioaugmentation이 간헐폭기 오수처리장치의 운전효율에 미치는 영향

In order to improve reactor performance of existing sewage treatment plants, the feasibility of enhancing reactor performance by bioaugmentation using EM as bioaugmentation agent and the effects of anoxic: oxic time ratio on reactor performance were investigated. Continuous and intermittent aeration modes were compared under the 6 hr of HRT. Three different types of intermittent aeration modes, that is, 15 min, of anoxic:45 min of oxic, 30 min of anoxic: 30 min of oxic, and 45 min of anoxic: 15 min oxic respectively were chosen as test modes to study the effects of anoxic : oxic time ratios on reactor performance. The optimum anoxic: oxic time ratio was 30 min:30 min when considering simultaneous removal of organic, nitrogen and phosphorus. When applying EM into a continuously aerated reactor under the varying dosing rates of 50-200 ppm, reactor performance in terms of organic and nitrogen removal efficiencies was not improved at all. Nitrogen removal efficiency was increase when the EM dosing rate was increased. However the degree of improvement was slight when the EM was injected above 100 ppm. However optimum phosphorus removal was found at the EM dosing of 200 ppm. Thus it was found that optimum injection concentration of EM is 200 ppm. It is apparent that putting EM into a sewage treatment plant significantly affects the T-N removal efficiency of the reactor by enhancing denitrification efficiency especially in operational conditions of relatively long anoxic periods. To achieve reciprocal condition in a reactor with intermittent aeration it is necessary to enhance the reactor performance by EM injection. In the case of modifying existing continuously aerated reactors into intermittent aerated reactors, it is obvious that operating costs of aeration would be reduced by reducing aeration time when compared with existing conventional sewage treatment plants.

Wastewater nitrification using ceramic industry waste

The presence of nitrogen in wastewater can cause eutrophication as well as health problems. Recent, more restrictive, legislation in Europe means that wastewater treatment systems should now be able to remove nitrogen; in many cases older plants, which were originally built without this objective, are currently being modified to include it. This paper presents the results obtained from a study using a pilot plant consisting of a biological aerated filter. The main goal of this experiment was to achieve nitrification, the most critical phase of the nitrification–denitrification process. The pilot plant was full-scale height with a pilot-scale cross-sectional area. The material used as biofilm support was a waste product from the ceramic industry. The influent was the primary effluent of a conventional sewage treatment plant. The flow was counter-current flow. The optimum amount of oxygen that needed to be supplied was studied. When only the biochemical oxygen demand (BOD5) and suspended solids (SS) requirements of the European Union Directive 91/271 CEE (European Economic Community) were fulfilled, [Formula: see text] and [Formula: see text] effluent concentrations of 24 mg [Formula: see text] and 36 mg [Formula: see text] were obtained. However, in order to achieve effluent concentrations of 10 mg [Formula: see text] and 91 mg [Formula: see text], the volumetric size requirements of the biological filter were increased by 4·2:1, equivalent to a maximum admissible BOD5volumetric load decrease from 6·33 to 1·51 kg BOD5/m3per day.

Wastewater nitrification using ceramic industry waste

The presence of nitrogen in wastewater can cause eutrophication as well as health problems. Recent, more restrictive, legislation in Europe means that wastewater treatment systems should now be able to remove nitrogen; in many cases older plants, which were originally built without this objective, are currently being modified to include it. This paper presents the results obtained from a study using a pilot plant consisting of a biological aerated filter. The main goal of this experiment was to achieve nitrification, the most critical phase of the nitrification–denitrification process. The pilot plant was full-scale height with a pilot-scale cross-sectional area. The material used as biofilm support was a waste product from the ceramic industry. The influent was the primary effluent of a conventional sewage treatment plant. The flow was counter-current flow. The optimum amount of oxygen that needed to be supplied was studied. When only the biochemical oxygen demand (BOD5) and suspended solids (SS) requirements of the European Union Directive 91/271 CEE (European Economic Community) were fulfilled, and effluent concentrations of 24 mg and 36 mg were obtained. However, in order to achieve effluent concentrations of 10 mg and 91 mg , the volumetric size requirements of the biological filter were increased by 4·2:1, equivalent to a maximum admissible BOD5 volumetric load decrease from 6·33 to 1·51 kg BOD5/m3 per day.

Plant-biofilm oxidation ditch for in situ treatment of polluted waters

Eutrophication of surface water bodies is a problem of increasing environmental and ecological concern worldwide and is particularly serious in China. In the present study, oxidation ditches were connected to a lake receiving municipal sewage sludges. Two 24 m 2 (width 2 m, length 12 m) parallel plastic oxidation ditches material were installed on a lake near the inlet of the municipal sewage. Zizania caduciflora and Canna generalis were grown in the ditches with plastic floating supporters for the removal of N and P from the sewage. The experiment was conducted firstly with municipal sewage in autumn–winter seasons for about 150 days under the following conditions: 2 m 3/h influent flow, 0.75 kW jet-flow aerator (air/water of 5), 18 h HRT (hydrological retention time) and a return ratio of 10. Then it was run with the polluted lake water in summer–autumn for about 160 days with an aerator of 1.25 kW and an influent of 6 m 3/h (air/water 3.3, HRT 6 h). The performance was quite stable during the experimental period for the municipal sewage treatment. The average removal rates of COD (chemical oxygen demand), SS (suspended solids), TP (total phosphorus), NH 4 +-N and inorganic-N were 70.6, 75.8, 72.6, 52.1 and 50.3%, respectively. For the polluted lake water treatment, the average concentrations of COD, NH 4 +-N and TP were 42.7, 13.1 and 1.09 mg/L, respectively, in the influent and were 25.1, 6.4 and 0.38 mg/L, respectively, in the effluent. The capacity of the plants to remove N and P by direct uptake was limited, but the indirect mechanisms also occurred. The proposed process, transforming the natural lake into a wastewater treatment plant, could evidently reduce the costs of the sewage collection, the land space requirement and the construction compared with conventional sewage treatment plants, and is especially suited to conditions in south China and south-east Asia.

Anaerobic Processes as the Core Technology for Sustainable Domestic Wastewater Treatment: Consolidated Applications, New Trends, Perspectives, and Challenges

Anaerobic digesters have been responsible for the removal of large fraction of organic matter (mineralization of waste sludge) in conventional aerobic sewage treatment plants since the early years of domestic sewage treatment (DST). Attention on the anaerobic technology for improving the sustainability of sewage treatment has been paid mainly after the energy crisis in the 1970s. The successful use of anaerobic reactors (especially up-flow anaerobic sludge blanket (UASB) reactors) for the treatment of raw domestic sewage in tropical and sub-tropical regions (where ambient temperatures are not restrictive for anaerobic digestion) opened the opportunity to substitute the aerobic processes for the anaerobic technology in removal of the influent organic matter. Despite the success, effluents from anaerobic reactors treating domestic sewage require post-treatment in order to achieve the emission standards prevailing in most countries. Initially, the composition of this effluent rich in reduced compounds has required the adoption of post-treatment (mainly aerobic) systems able to remove the undesirable constituents. Currently, however, a wealth of information obtained on biological and physical-chemical processes related to the recovery or removal of nitrogen, phosphorus and sulfur compounds creates the opportunity for new treatment systems. The design of DST plant with the anaerobic reactor as core unit coupled to the pre- and post-treatment systems in order to promote the recovery of resources and the polishing of effluent quality can improve the sustainability of treatment systems. This paper presents a broader view on the possible applications of anaerobic treatment systems not only for organic matter removal but also for resources recovery aiming at the improvement of the sustainability of DST.

Elimination of aromatic surfactants from municipal wastewaters: comparison of conventional activated sludge treatment and membrane biological reactor

Behaviour of anionic surfactants of linear alkylbenzene sulphonates (LAS) type and non-ionic surfactants of nonylphenol polyethoxylate (NPnEO) type was studied in the conventional mechanical/biological sewage treatment plant (STP) as well as using a membrane biological reactor (MBR). LAS and NPnEO were determined using high performance liquid chromatography (HPLC) equipped with spectrofluorimetric detection. Liquid chromatography/tandem mass spectrometry (LC/MS/MS) was used for identification and quantification of stable metabolites, including nonylphenol (NP), nonylphenol monoethoxylate (NP1EO), nonylphenol diethoxylate (NP2EO) and nonylphenoxy carboxylic acids (NPnEC). The study showed that aromatic surfactants belong to the most prominent constituents in the examined municipal wastewaters with typical LAS and NPnEO concentrations of 2-10 mg/L and 0.1-0.5 mg/L, respectively. The removal of aromatic surfactants in conventional STP showed well-known features reported in the literature, including an efficient microbial transformation of the parent molecules and formation of stable metabolic products. The elimination efficiency of aromatic surfactants using the MBR unit was higher than that in the conventional STP, while the composition of recalcitrant nonylphenolic residues in the effluent seems to be ecotoxicologically more favourable due to the lower contributions of the lipophilic metabolites.

Fate of indigenous bacteriophage in a membrane bioreactor

Indigenous bacteriophage was isolated from a conventional sewage treatment plant treating a largely domestic wastewater. The isolated phage was T-even-like with a mean size of 200 nm and was used to indicate the viral removal efficiency achieved in a bench-scale membrane bioreactor (MBR). The MBR incorporated three flat microfiltration membrane modules which were polyethylene with a pore size of 0.4 μm. When treating settled domestic sewage, the MBR achieved an overall removal rate of phage of 2.3–5.9 log across the treatment process. The membrane alone demonstrated a poor phage removal efficiency, but removal efficiency increased as the filtration resistance was increased. It was proposed therefore, that the biofilm accumulating on the surface of the membrane made a major contribution to phage removal. The MBR demonstrated an almost complete removal of faecal coliforms and faecal streptococci (up to 7 log). By comparison a full-scale treatment plant treating the same settled sewage and incorporating tertiary treatment, achieved only up to 2 log removal of the same excreted phage and bacteria.

Variation in heavy metal removal by a conventional municipal waste water treatment plant

It is known that there are many factors which affect the removal of metals in conventional sewage treatment plant. The purpose of this research was the determination of ten metals (Fe, Cu, Zn, Mn, Pb, Cd, Cr, Ni, V, Li) in the wastewater of the town of Kavala (80,000 population), at the inlet and at the outlet of the waste water treatment plant under different conditions (strong rainfall, an average day and during holidays). The previously mentioned conditions showed the effect they have on the concentration of heavy metals in untreated waste water (the strong rainfall increases the concentrations of the Fe, Cu, Zn, Cr and Pb, and the holidays reduces the concentrations of the Fe, Cu, Zn, Mn, Ni, Pb and Cd) and the removal ability of metals during the treatment.

The bioaugmentation of sequencing batch reactor sludges for biological phosphorus removal

The development of enhanced biological phosphorus removal (EBPR) through the bioaugmentation of a conventional activated sludge was studied. The objectives of the study were to evaluate the phosphorus removal capability of a sequencing batch reactor (SBR) when started with conventional activated sludge and augmented with a pure culture of Acinetobacter lwoffii. The effect of the addition of the pure culture on the reactor start up time, the settling properties of the sludge and on COD and nitrogen removal was also investigated. The effect of the removal of up to 70% of the bioaugmented biomass and its substitution with unconditioned sludge from a conventional sewage treatment plant was determined. This study has demonstrated that bioaugmentation can convert a conventional sewage works activated sludge to an EBPR sludge in 14 days. The sludge produced shows resilience to influent phosphate fluctuations, low D.O. and biomass replacement. The COD and nitrogen removal capabilities of the sludge and its settling properties are not affected by the addition of the pure culture.

The bioaugmentation of sequencing batch reactor sludges for biological phosphorus removal

The development of enhanced biological phosphorus removal (EBPR) through the bioaugmentation of a conventional activated sludge was studied. The objectives of the study were to evaluate the phosphorus removal capability of a sequencing batch reactor (SBR) when started with conventional activated sludge and augmented with a pure culture of Acinetobacter lwofii. The effect of the addition of the pure culture on the reactor start up time, the settling properties of the sludge and on COD and nitrogen removal was also investigated. The effect of the removal of up to 70% of the bioaugmented biomass and its substitution with unconditioned sludge from a conventional sewage treatment plant was determined. This study has demonstrated that bioaugmentation can convert a conventional sewage works activated sludge to an EBPR sludge in 14 days. The sludge produced shows resilience to influent phosphate fluctuations, low D.O. and biomass replacement. The COD and nitrogen removal capabilities of the sludge and its settling properties are not affected by the addition of the pure culture.

Komplexbildner in alkalischen Reinigern

Using a laboratory-scale CIP test rig under process conditions (temperature fluid dynamics, time) based on values found in practical cleaning of dairy plant heat exchangers comparative cleaning experiments were carried out. For testing circular stainless steel elements of 50 mm in diameter were used which had been soiled with deposits consisting mainly of denatured whey proteins in a specific heating procedure using fresh raw milk. Deposit removal was monitored by use of a video camera. Single digitized frames showing different stages of soil removal were transmitted to a computer and analyzed with the aid of an image processing software (surface clean/ still soiled). As a basic substrate an aqueous solution of sodium hydroxide in tap water (17°dH) was used to which 12 complexing agents had been added in a comparable concentration. According to the test results EDTA is still the most efficient product, although due to its poor biodegradability in conventional sewage treatment plants, it should be substituted by other substrates. Na3-SDA proved to be nearly as efficient as EDTA, but due to its high production costs it is, at present not competitive on the market. NTA, which is recommended by the Ministry for Environment and Reactor Safety, Bonn, and the Federal Health Office, Berlin, was found as a well suited biodegradable substitute for ETDA. The biodegradable structures Na 3 -MGDA (Trilon ES 9964), Na 3 -EGDA and Na 4 -ASDA were as effective as NTA, whilst IDA and Na 2 -IDA as well as Na 2 -MIDA, Na 2 -HEIDA, and NA 3 -ISDA produced no effect. With respect to its comparability to NTA, and the justifiable production costs, Na 3 -MGDA (Trilon ES 9964) is the product of choice for a field test for cleaning a plate heat exchanger in a dairy plant.

Technical economic analysis of stabilization ponds

Employing stabilization pond systems to treat wastewater has the advantages of being economical of energy, easy to operate, and low in operation costs. However, stabilization pond systems have the problem of occupying large areas of land. Therefore, only after an overall technical economic analysis is made can an assessment be made of whether it is feasible to employ a stabilization pond systems to treat wastewater. During the period of the Seventh Five-year Plan of China, the “Study on the Technology of Stabilization Ponds” was set as one of the national scientific and technological key items. Seven experimental bases were established ranging from the north down to the south of China. With the great numbers of operational data obtained from both these bases and the existing stabilization pond systems, an analysis of the composition of the capital outlay in the stabilization pond system construction was made. The analysis shows that the land purchase cost accounts for approximately 60% of the capital outlay in construction and is the most important influencing factor. A comparison between the various costs of stabilization pond systems and those of conventional sewage treatment plant was made. Thereupon two new parameters were put forward: “equal capital land cost” and “upper limit of feasible land cost”. At the same time, a nationwide isogram of these two parameters was plotted. This isogram may be useful for preliminary design and planning purposes, and may be helpful to the users to assess comparatively easily whether its feasible to employ stabilization pond system.

Technical economic analysis of stabilization ponds

Employing stabilization pond systems to treat wastewater has the advantages of being economical of energy, easy to operate, and low in operation costs. However, stabilization pond systems have the problem of occupying large areas of land. Therefore, only after an overall technical economic analysis is made can an assessment be made of whether it is feasible to employ a stabilization pond systems to treat wastewater. During the period of the Seventh Five-year Plan of China, the “Study on the Technology of Stabilization Ponds” was set as one of the national scientific and technological key items. Seven experimental bases were established ranging from the north down to the south of China. With the great numbers of operational data obtained from both these bases and the existing stabilization pond systems, an analysis of the composition of the capital outlay in the stabilization pond system construction was made. The analysis shows that the land purchase cost accounts for approximately 60% of the capital outlay in construction and is the most important influencing factor. A comparison between the various costs of stabilization pond systems and those of conventional sewage treatment plant was made. Thereupon two new parameters were put forward: “equal capital land cost” and “upper limit of feasible land cost”. At the same time, a nationwide isogram of these two parameters was plotted. This isogram may be useful for preliminary design and planning purposes, and may be helpful to the users to assess comparatively easily whether its feasible to employ stabilization pond system.

Upgrading and nitrification by submerged bio-film reactors - experiences from a large scale plant

The upgrading and nitrification was a requirement in 1986 for the conventional sewage treatment plant Geiselbullach, west of Munich, Germany, designed for 250 000 inhabitants equivalents. The possibility was tested to use submerged bio-film reactors in the aeration tanks to increase the MLSS concentration. Half-scale experiments were undertaken with three different reactor types. A rope type material, called Ring-laceR was selected for the large-scale application, because it did not produce anaerobic sludge deposits, as the other tested reactor types did. The design criteria had to be developed. The process operation started in January 1988; a few months later the phosphorus removal by chemical precipitation was also put into operation. After stable conditions were assured the concentration of the MLSS could be increased to about 10 g/l, due to sludge volume indices of about 50, formerly 180 to 300. A nearly complete nitrification was achieved, which could even be continued in winter times at water temperatures of 8 to 10 °C. Many highly developed microorganisms in the sessile sludge occurred (nematodes, tubifex…), which grew excessively under certain conditions and reduced the normal bacteria to unacceptable low quantities. A worm cure could reduce the worms to acceptable counts. Problems with the longtime stability of the material arose and were investigated.

Monitoring of the Santos Submarine Outfall, São Paulo, Brazil, 10 Years in Operation

This summary is based on several reports accompanying the performance of the Emissary in operation since 1979 that are analyzed together with the operational data of the Preconditioning Station of Santos Sewer, State of São Paulo, Brazil. The choice of the pre-treatment system and the emissary was made due to the regional absence of areas ample enough to install a complete conventional sewage treatment plant and to the fact that the economical studies showed the advantage of the construction of an outfall sewer taking into account the difference in cost between primary and secondary treatment of waste. The efficiency of the dimension of the minimal extension adopted is verified for the various trajectories of the maritime currents and their predominant cycles. The principal physical, chemical and biological parameters were collected from 14,309 analyses of the last four campaigns (1976, 1979, 1982 and 1986). They are analyzed together, permitting the verification of the efficiency of the oceanic sewage disposal. The results of the campaigns generate recommendations and conclusions, contributing with details for future projects and also permitting other countries of the Americas to evaluate and compare the operational performance of their emissaries.