Integrated management of urban wastewater systems: a model-based approach

The main objective pursued in this thesis targets the development and systematization of a methodology that allows addressing management problems in the dynamic operation of Urban Wastewater Systems. The proposed methodology will suggest operational strategies that can improve the overall performance of the system under certain problematic situations through a model-based approach. The proposed methodology has three main steps: The first step includes the characterization and modeling of the case-study, the definition of scenarios, the evaluation criteria and the operational settings that can be manipulated to improve the system’s performance. In the second step, Monte Carlo simulations are launched to evaluate how the system performs for a wide range of operational settings combinations, and a global sensitivity analysis is conducted to rank the most influential operational settings. Finally, the third step consists on a screening methodology applying a multi-criteria analysis to select the best combinations of operational settings.

Knowledge-based modelling and simulation of operational problems of microbiological origin in wastewater treatment plants

The activated sludge and anaerobic digestion processes have been modelled in widely accepted models. Nevertheless, these models still have limitations when describing operational problems of microbiological origin. The aim of this thesis is to develop a knowledge-based model to simulate risk of plant-wide operational problems of microbiological origin.For the risk model heuristic knowledge from experts and literature was implemented in a rule-based system. Using fuzzy logic, the system can infer a risk index for the main operational problems of microbiological origin (i.e. filamentous bulking, biological foaming, rising sludge and deflocculation). To show the results of the risk model, it was implemented in the Benchmark Simulation Models. This allowed to study the risk model's response in different scenarios and control strategies. The risk model has shown to be really useful providing a third criterion to evaluate control strategies apart from the economical and environmental criteria.

Operation and control of SBR processes for enhanced biological nutrient removal from wastewater

In the last decades, the awareness of environmental issues has increased in society considerably. There is an increasing need to improve the effluent quality of domestic wastewater treatment processes. This thesis describes the application of the Sequencing Batch Reactor (SBR) technology for Biological Nutrient Removal (BNR) from the wastewater. In particular, the work presented evolves from the nitrogen removal to the biological nutrient removal (i.e. nitrogen plus phosphorous removal) with special attention to the operational strategy design, the identification of possible reactor cycle controls or the influent composition related to the process efficiency. In such sense, also the use of ethanol as an external carbon (when low influent Carbon:Phosphorus (C:P) or Carbon:Nitrogen (C:N) ratios are presented) are studied as an alternative to maintain the BNR efficiency.

Management of industrial wastewater discharges in river basins through agents'argumentation

La gestió de l'aigua residual és una tasca complexa. Hi ha moltes substàncies contaminants conegudes però encara moltes per conèixer, i el seu efecte individual o col·lgectiu és difícil de predir. La identificació i avaluació dels impactes ambientals resultants de la interacció entre els sistemes naturals i socials és un assumpte multicriteri. Els gestors ambientals necessiten eines de suport pels seus diagnòstics per tal de solucionar problemes ambientals. Les contribucions d'aquest treball de recerca són dobles: primer, proposar l'ús d'un enfoc basat en la modelització amb agents per tal de conceptualitzar i integrar tots els elements que estan directament o indirectament involucrats en la gestió de l'aigua residual. Segon, proposar un marc basat en l'argumentació amb l'objectiu de permetre als agents raonar efectivament. La tesi conté alguns exemples reals per tal de mostrar com un marc basat amb agents que argumenten pot suportar diferents interessos i diferents perspectives. Conseqüentment, pot ajudar a construir un diàleg més informat i efectiu i per tant descriure millor les interaccions entre els agents. En aquest document es descriu primer el context estudiat, escalant el problema global de la gestió de la conca fluvial a la gestiódel sistema urbà d'aigües residuals, concretament l'escenari dels abocaments industrials. A continuació, s'analitza el sistema mitjançant la descripció d'agents que interaccionen. Finalment, es descriuen alguns prototips capaços de raonar i deliberar, basats en la lògica no monòtona i en un llenguatge declaratiu (answer set programming). És important remarcar que aquesta tesi enllaça dues disciplines: l'enginyeria ambiental (concretament l'àrea de la gestió de les aigües residuals) i les ciències de la computació (concretament l'àrea de la intel·ligència artificial), contribuint així a la multidisciplinarietat requerida per fer front al problema estudiat. L'enginyeria ambiental ens proporciona el coneixement del domini mentre que les ciències de la computació ens permeten estructurar i especificar aquest coneixement.

SBR technology for wastewater treatment: suitable operational conditions for a nutrient removal

Actualment, la legislació ambiental ha esdevingut més restrictiva pel que fa a la descàrrega d'aigües residuals amb nutrients, especialment en les anomenades àrees sensibles o zones vulnerables. Arran d'aquest fet, s'ha estimulat el coneixement, desenvolupament i millora dels processos d'eliminació de nutrients. El Reactor Discontinu Seqüencial (RDS) o Sequencing Batch Reactor (SBR) en anglès, és un sistema de tractament de fangs actius que opera mitjançant un procediment d'omplerta-buidat. En aquest tipus de reactors, l'aigua residual és addicionada en un sol reactor que treballa per càrregues repetint un cicle (seqüència) al llarg del temps. Una de les característiques dels SBR és que totes les diferents operacions (omplerta, reacció, sedimentació i buidat) es donen en un mateix reactor. La tecnologia SBR no és nova d'ara. El fet, és que va aparèixer abans que els sistema de tractament continu de fangs actius. El precursor dels SBR va ser un sistema d'omplerta-buidat que operava en discontinu. Entre els anys 1914 i 1920, varen sorgir certes dificultats moltes d'elles a nivell d'operació (vàlvules, canvis el cabal d'un reactor a un altre, elevat temps d'atenció per l'operari...) per aquests reactors. Però no va ser fins a finals de la dècada dels '50 principis del '60, amb el desenvolupament de nous equipaments i noves tecnologies, quan va tornar a ressorgir l'interès pels SBRs. Importants millores en el camp del subministrament d'aire (vàlvules motoritzades o d'acció pneumàtica) i en el de control (sondes de nivell, mesuradors de cabal, temporitzadors automàtics, microprocessadors) han permès que avui en dia els SBRs competeixin amb els sistemes convencional de fangs actius. L'objectiu de la present tesi és la identificació de les condicions d'operació adequades per un cicle segons el tipus d'aigua residual a l'entrada, les necessitats del tractament i la qualitat desitjada de la sortida utilitzant la tecnologia SBR. Aquestes tres característiques, l'aigua a tractar, les necessitats del tractament i la qualitat final desitjada determinen en gran mesura el tractament a realitzar. Així doncs, per tal d'adequar el tractament a cada tipus d'aigua residual i les seves necessitats, han estat estudiats diferents estratègies d'alimentació. El seguiment del procés es realitza mitjançant mesures on-line de pH, OD i RedOx, els canvis de les quals donen informació sobre l'estat del procés. Alhora un altre paràmetre que es pot calcular a partir de l'oxigen dissolt és la OUR que és una dada complementària als paràmetres esmentats. S'han avaluat les condicions d'operació per eliminar nitrogen d'una aigua residual sintètica utilitzant una estratègia d'alimentació esglaonada, a través de l'estudi de l'efecte del nombre d'alimentacions, la definició de la llargada i el número de fases per cicle, i la identificació dels punts crítics seguint les sondes de pH, OD i RedOx. S'ha aplicat l'estratègia d'alimentació esglaonada a dues aigües residuals diferents: una procedent d'una indústria tèxtil i l'altra, dels lixiviats d'un abocador. En ambdues aigües residuals es va estudiar l'eficiència del procés a partir de les condicions d'operació i de la velocitat del consum d'oxigen. Mentre que en l'aigua residual tèxtil el principal objectiu era eliminar matèria orgànica, en l'aigua procedent dels lixiviats d'abocador era eliminar matèria orgànica i nitrogen. S'han avaluat les condicions d'operació per eliminar nitrogen i fòsfor d'una aigua residual urbana utilitzant una estratègia d'alimentació esglaonada, a través de la definició del número i la llargada de les fases per cicle, i la identificació dels punts crítics seguint les sondes de pH, OD i RedOx. S'ha analitzat la influència del pH i la font de carboni per tal d'eliminar fòsfor d'una aigua sintètica a partir de l'estudi de l'increment de pH a dos reactors amb diferents fonts de carboni i l'estudi de l'efecte de canviar la font de carboni. Tal i com es pot veure al llarg de la tesi, on s'han tractat diferents aigües residuals per a diferents necessitats, un dels avantatges més importants d'un SBR és la seva flexibilitat.

Statistical modeling suggests that antiandrogens in effluents from wastewater treatment works contribute to widespread sexual disruption in fish living in English rivers.

BACKGROUND: The widespread occurrence of feminized male fish downstream of some wastewater treatment works has led to substantial interest from ecologists and public health professionals. This concern stems from the view that the effects observed have a parallel in humans, and that both phenomena are caused by exposure to mixtures of contaminants that interfere with reproductive development. The evidence for a "wildlife-human connection" is, however, weak: Testicular dysgenesis syndrome, seen in human males, is most easily reproduced in rodent models by exposure to mixtures of antiandrogenic chemicals. In contrast, the accepted explanation for feminization of wild male fish is that it results mainly from exposure to steroidal estrogens originating primarily from human excretion. OBJECTIVES: We sought to further explore the hypothesis that endocrine disruption in fish is multi-causal, resulting from exposure to mixtures of chemicals with both estrogenic and antiandrogenic properties. METHODS: We used hierarchical generalized linear and generalized additive statistical modeling to explore the associations between modeled concentrations and activities of estrogenic and antiandrogenic chemicals in 30 U.K. rivers and feminized responses seen in wild fish living in these rivers. RESULTS: In addition to the estrogenic substances, antiandrogenic activity was prevalent in almost all treated sewage effluents tested. Further, the results of the modeling demonstrated that feminizing effects in wild fish could be best modeled as a function of their predicted exposure to both anti-androgens and estrogens or to antiandrogens alone. CONCLUSION: The results provide a strong argument for a multicausal etiology of widespread feminization of wild fish in U.K. rivers involving contributions from both steroidal estrogens and xeno-estrogens and from other (as yet unknown) contaminants with antiandrogenic properties. These results may add farther credence to the hypothesis that endocrine-disrupting effects seen in wild fish and in humans are caused by similar combinations of endocrine-disrupting chemical cocktails.

Cloacibacterium normanense gen. nov., sp nov., a novel bacterium in the family Flavobacteriaceae isolated from municipal wastewater

Phenotypic and phylogenetic studies were performed on three isolates of an unknown Gram-negative, facultatively anaerobic, non-motile, yellow-pigmented, rod-shaped organism isolated from raw sewage. 16S rRNA gene sequence analysis indicated that these strains were members of the Bergeyella-Chryseobacterium-Riemerella branch of the family Flavobacteriaceae. The unknown bacterium was readily distinguished from reference strains by 16S rRNA gene sequencing and biochemical tests. The organism contained menaquinone MK-6 as the predominant respiratory quinone and had a DNA G + C content of 31 mol%. A most probable number-PCR approach was developed to detect, and estimate the numbers of, this organism. Untreated wastewater from one plant yielded an estimated count of 1.4 x 10(5) cells ml(-1), and untreated wastewater from a second plant yielded an estimated count of 1.4 x 10(4) cells ml(-1). Signal was not detected from treated effluent or from human stool specimens. On the basis of the results of the study presented, it is proposed that the unknown bacterium be classified in a novel genus Cloacibacterium, as Cloacibacterium normanense gen. nov., sp. nov., which is also the type species. The type strain of Cloacibacterium normanense is strain NRS1(T) (=CCUG 46293(T)=CIP 108613(T) =ATCC BAA-825(T) = DSM 15886(T)).

Review of the potential for co-firing of cassava rhizome for generating heat and power in cassava based bio-ethanol plant in Thailand

Biomass is an important source of energy in Thailand and is currently the main renewable energy source, accounting for 40% of the renewable energy used. The Department of Alternative Energy and E�ciency (DEDE), Ministry of Thailand, has been promoting the use of renewable energy in Thailand for the past decade. The new target for renewable energy usage in the country is set at 25% of the �nal energy demand in 2021. Thailand is the world’s fourth largest producer of cassava and this results in the production of signi�cant amounts of cassava rhizome which is a waste product. Cassava rhizome has the potential to be co-�red with coal for the production of heat and power. With suitable co-�ring ratios, little modi�cation will be required in the co-�ring technology. This review article is concerned with an investigation of the feasibility of co-�ring cassava rhizome in a combined heat and power system for a cassava based bio-ethanol plant in Thailand. Enhanced use of cassava rhizome for heat and power production could potentially contribute to a reduction of greenhouse gas emissions and costs, and would help the country to meet the 2021 renewable energy target.

High pressure intensification of cassava resistant starch (RS3) yields

Cassava starch, typically, has resistant starch type 3 (RS3) content of 2.4%. This paper shows that the RS3 yields can be substantially enhanced by debranching cassava starch using pullulanase followed by high pressure or cyclic high-pressure annealing. RS3 yield of 41.3% was obtained when annealing was carried out at 400 MPa/60°C for 15 min, whereas it took nearly 8 h to obtain the same yield under conventional atmospheric annealing at 60°C. The yield of RS3 could be further significantly increased by annealing under 400MPa/60°C pressure for 15 min followed by resting at atmospheric pressure for 3 h 45 min, and repeating this cycle for up to six times. Microstructural surface analysis of the product under a scanning electron microscope showed an increasingly rigid density of the crystalline structure formed, confirming higher RS3 content.

Sanitation assessment of wastewater treated by stabilization ponds for potential reuse in agricultural irrigation sanitation assessment

Wastewater reuse has become an important alternative to agricultural irrigation; on the other hand, it poses concern with regard to public health. Total coliform and Escherichia coli concentration, presence of helminth eggs and Salmonella, and physical-chemical parameters were evaluated in raw and treated wastewater. Chemical and biochemical oxygen demand removal efficiency was 74.6 and 77.9%, respectively. As for organic nitrogen, total phosphorus, and total suspended solids, total efficiency removal was 17.4, 12.5, and 32.9%, respectively. The average density of total coliforms and E. coli was 3.5 x 10(9) and 1.8 x 10(8) MPN/100 mL and 1.1 x 10(7) MPN/100 mL and 3.9 x 10(5) MPN/100 mL for raw and treated wastewater, respectively. Ascaris eggs were observed in 80.8% of the samples collected, and viable eggs in 42.3% of the samples. Salmonella was detected in 36.4% of the samples. The values observed in treated wastewater did not show the adequate bacteriological quality, as recommended by World Health Organization (Geneva, Switzerland). Therefore, additional measures should be taken to achieve an improved microbiological and parasitological quality.

Dynamics of Aeromonas species isolated from wastewater treatment system

Aeromonas are widely distributed in the aquatic environment, and are considered to be emerging organisms that can produce a series of virulence factors. The present study was carried out in a sanitary sewage stabilization pond treatment system, located in Lins, State of Sao Paulo, Brazil. Most probable number was applied for estimation of the genus Aeromonas. Colony isolation was carried out on blood agar ampicillin and confirmed by biochemical characterization. Aeromonas species were isolated in 72.4% of influent samples, and in 55.2 and 48.3% of effluent from anaerobic and facultative lagoons, respectively. Thirteen Aeromonas species were isolated, representing most of the recognized species of these organisms. Even though it was possible to observe a tendency of decrease, total elimination of these organisms from the studied system was not achieved. Understanding of the pathogenic organism`s dynamics in wastewater treatment systems with a reuse potential is especially important because of the risk it represents.

Effect of enzymatic pretreatment and increasing the organic loading rate of lipid-rich wastewater treated in a hybrid UASB reactor

This study aimed at evaluating the effect of increasing organic loading rates and of enzyme pretreatment on the stability and efficiency of a hybrid upflow anaerobic sludge blanket reactor (UASBh) treating dairy effluent. The UASBh was submitted to the following average organic loading rates (OLR) 0.98 Kg.m(-3).d(-1), 4.58 Kg.m(-3).d(-1), 8.89 Kg.m(-3).d(-1) and 15.73 Kg.m(-3).d(-1), and with the higher value, the reactor was fed with effluent with and without an enzymatic pretreatment to hydrolyze fats. The hydraulic detention time was 24 h, and the temperature was 30 +/- 2 degrees C. The reactor was equipped with a superior foam bed and showed good efficiency and stability until an OLR of 8.89 Kg.m(-3).d(-1). The foam bed was efficient for solid retention and residual volatile acid concentration consumption. The enzymatic pretreatment did not contribute to the process stability, propitiating loss in both biomass and system efficiency. Specific methanogenic activity tests indicated the presence of inhibition after the sludge had been submitted to the pretreated effluent It was concluded that continuous exposure to the hydrolysis products or to the enzyme caused a dramatic drop in the efficiency and stability of the process, and the single exposure of the biomass to this condition did not inhibit methane formation. (C) 2011 Elsevier B.V. All rights reserved.