In this thesis, a chirp-controlled pump-probe system has been developed to investigate the role of chirp in mode-locking mechanism. By modulating pump power and focusing condition, power, chirp, and wavelength dependent transient reflectivity ( £GR /R), pulse duration, and amplitude ratio in pump-probe measurement for the multiply-strained-quantum-well saturable Bragg reflector (SSBR) are presented. According this study, one can find a more efficient and stable mode-locking mechanism through proper chirp arrangement inside cavity. Compared to the case of transform-limited pump condition, shorter fast-carrier-lifetime and smaller amplitude ratio of slow and fast relaxation contribution are observed in negative chirp excitation condition. Meanwhile, we can see that there is a shorter fast-carrier-lifetime and a smaller amplitude ratio in case of excitation pulse with -25000 ( fs^2 ) chirp or increasing fluence ¡]2 £gm/cm^2->12 £gm/cm^2 ¡^. The results show that the pulse compression strength is stronger in -25000 ( fs^2 ) chirp and full with the tendency demonstrated by pulse shaping factor. All of these experimental results show that -25000 ( fs^2 ) chirp is the best chirped control condition to make mode-locking more efficient and stable. In addition, with the increasing fluence ¡]2 ->12 £gm/cm^2 ¡^, three times of saturable fluence, a more stable and efficient mode-locking condition is expectable.

The principle aim of this study was to gain an understanding of the conditions and processes governing the occurrence of simultaneous nitrification and denitrification (SND). SND is the process that combines nitrification and denitrification in the same reactor (at the same time) under fully aerobic conditions. From various studies, two main hypotheses, one physical and one biological, have been proposed to explain SND (Simultaneous Nitrification and Denitrification). Significant research has been performed on the biological aspects, whereas relatively little is known about the physical explanation. Therefore, further investigations of physical explanation on SND (Simultaneous Nitrification and Denitrification) are carried out in this thesis. To fulfill this principal objective, two major tasks were preformed: experimental studies and model development. The experimental investigation was conducted using lab scale sequencing batch reactors (SBR). The operating conditions of the reactors were varied corresponding to the aim of each experiment. The influent wastewater was collected from the effluent of an anaerobic pond at an abattoir wastewater treatment plant. The main experimental studies focused on three factors, the effect of soluble organic carbon, floc size and dissolved oxygen (DO) concentrations, on the SND activity. The results revealed that all these factors had a significant influence on the degree of SND achieved. Almost 50% of inorganic nitrogen lost by SND (Simultaneous Nitrification and Denitrification) could be achieved when operating at a soluble COD:TKN ratio of 6. A dramatic increase in SND activity to 85% was found when this ratio reached 10. With a soluble COD:TKN ratio of 15, complete nitrogen removal by SND could be achieved. The effect of dissolved oxygen (DO) was equally strong. SND could completely occur at very low DO concentrations (0.2 mg/L). However, the nitrogen removal in this range was substantially limited by the low nitrification rate. To improve the nitrification rate but still achieve effective denitrification, a DO concentration of around 0.4-0.5 mg/L seems to be an optimal value to maintain a significant degree of SND. In this range, the nitrification rate reached 50% of the rate found at DO of 1.1 mg/L and 60% SND activity was achieved. The effect of bacterial floc size on SND was also quite remarkable. It was found that an SBR operating with a median floc size of 80 mm could achieve 80% SND, whereas the SND activity decreased to only 50% after the median floc size was reduced to 40 mm in the following treatment cycle. A complete nitrogen balance over the whole process was performed to confirm the occurrence of SND in such systems. Under typical operating conditions, it was found that the nitrogen gas was the major nitrogen product of the treatment process (approximately 58% of the total output). 14% of nitrogen was assimilated to biomass whereas 23 % of nitrogen at the end of the process was in the soluble form (organic nitrogen, nitrite, nitrate and ammonium). The mathematical dynamic model was developed to gain a better understanding of SND in the situation that is difficult to investigate experimentally. The overall model structure can be divided into 4 main areas : 1. a ‘micro’ level model for a single floc 2. the reaction rates for a single floc size 3. the reaction rates for the entire reactor considering the floc size distribution 4. a ‘macro’ model for the whole reactor including the operational changes throughout the cycle. It was found that the model can predict the SND behavior well for the system operating under typical influent characteristics (SCOD:TKN of 10). However, poor predictions were found at different levels of SCOD:TKN. Two crucial reasons can be given. Firstly, this model did not include intracellular carbon storage by bacteria. Secondly, many parameters, especially floc and microorganism characteristics (i.e. intra floc biomass distribution, growth and decay of the microorganism, etc.) could not be determined or estimated accurately. However, under normal operating conditions of this study, the model advances the fundamental understanding of SND process in activated sludge system. The simulation results showed that both floc diameter and liquid phase concentration are important factors influencing the internal floc concentrations. It was also predicted that an anoxic microzone, caused by oxygen diffusion limitation, potentially occurs in the floc center. This microzone therefore enhances denitrification activity inside the floc. A number of major conclusions can be drawn from this thesis: 1. SND potentially occurs as a result of physical phenomenon 2. high soluble COD is beneficial to SND activity 3. suitable floc size distribution (with more large flocs) can enhance SND 4. major nitrogenous product of the treatment process is nitrogen gas 5. dissolved oxygen optimization is critical to get good nitrification rate and SND.

No description available.

Tack vare att konstgräsplaner kan användas dygnets alla timmar och årets alla dagar och därmed är väldigt yteffektiva, blir de alltmer vanliga. Men frågor har lyfts om miljöaspekter kopplade till dem. Det har tidigare varit känt att konstgräsplaner är en källa till oönskade kemikalier och nyligen har de pekats ut som Sveriges näst största källa till läckage av mikroplastpartiklar. Sådana partiklar skulle kunna påverka biota negativt om de kommer ut i naturen. Då kunskapsläget var ovisst vad gällde migration av mikroplastpartiklar från konstgräsplaner via deras dränering gjordes därför våren 2016 provtagningar i dränerande brunnar vid ett antal utvalda konstgräsplaner i Södertälje kommun. För att kunna ge svar på om konstgräsplaner kan anses ha en miljöskadande påverkan, gjordes även en genomgång av krav och lagstiftning kopplat till dem. Beräknade mängder granulat som hittades vid provtagningar visade på små mängder och slutsatser dras därför att det måste vara annan migration än den via dränering som bidrar till konstgräsplaners stora läckage av mikroplastpartiklar. Dock visar studien att granulatet kan migrera via dräneringssystemet och därmed ta sig vidare till vattenmiljöer. Genomgång av krav och lagar visade att miljöaspekter kopplade till konstgräsplaner flera gånger är odefinierade och otydliga och ibland saknas helt. Frågor lyfts om konstgräsplaner borde ses som en sådan verksamhet där anmälan, tillstånd och tillsyn också utgår ifrån miljöperspektiv, samt vilka parter som har ansvar i frågan. Med ytterligare information om att en del av det fyllnadsmaterial som produceras i Sverige och därmed läggs ut på konstgräsplaner runt om i landet är klassat som avfall, väcks ytterligarefrågor om vem som bär ansvaret samt hur myndigheter tar ställning i frågan. Avslutningsvis ges åtgärdsförslag som skulle kunna hjälpa till i kommuners arbete för att minimera risker förmigration av gummigranulat vidare till naturen. / Pitches with artificial turf can be used at all hours and all year. They are therefore very space efficient and become increasingly common. But questions have been raised about the environmental issues that may arise from them. It has previously been known that artificial turf is a source of unwanted chemicals and recently they have been identified as the second biggest source of leakage of micro-plastic particles in Sweden. Such particles could affect biota negatively if they are released into nature. Since the state of knowledge was uncertain about migration of micro-plastic particles from artificial turf via their drainage, tests were made in draining wells at a selected number of artificial turf fields in municipality of Södertälje. To be able to answer if artificial turf is considered to have an environmentally damaging effect, a review of requirements and laws related to them were also made. Estimated quantities of granulate found during tests showed small amounts and conclusions were made that there must be another migration than through the drainage that contributes to the large leakage of micro particles of plastic from artificial turf. However, the study shows that the granulate can migrate through the drainage system and thus make it through to aquatic environments. Review of requirements and laws showed that environmental aspects linked to artificial turf several times are undefined and unclear and sometimes completely missing. Questions are raised if artificial turf should be seen as an activity where notification, authorization and supervision based on the environmental perspective are used, and which parties who have the responsibility in the matter. With additional information about that part of the filling material produced in Sweden and thus posted on artificial turf fields around the country are classified as waste, again raises questions about responsibility but also about governing agencies and their position on the subject. Concluding proposals are given for measures that could help to municipalities' efforts to minimize the risk of migration of rubber granules to nature.

In Sweden today many municipalities and sport clubs chooses to build artificial turfs becauseof the increased period of using the turfs during the year and less maintenance requirementsthan for natural grass fields. What could be problematic with artificial turfs is the rubbergranules used as infill material in the turf matt. The rubber granules are often made fromrecycled tires, which may contain for the human health and the environment, harmful substances.This was the reason why the Swedish Chemicals Agency commissioned a statusreport in 2006 which, among other things, concluded that the environmental and health risksassociated with granules made from recycled tiers in artificial turf fields were small, but thatthere could be a local environmental hazard. The purpose and objective of the risk assessmentwas to identify how artificial turf plans granules can affect recipients in the area closeto the pitches and provide input to reduce the spread of metals and substances harmful forboth human health and the surrounding environment. The work was divided into three parts:(1) the construction of artificial turf pitches and their material content, the spread of granulatesoutside the fields and disposal of artificial turf pitches. (2) Measured concentrations andsubstances from granulates and a review of environmental and health risk assessments fromthe literature. (3) Results from the studies own research and a brief risk assessment of artificialturf fields in Västerås. The research consisted of two parts. One mapping part, wherequestionnaires were sent out to a stratified sample of respondents and one part consisting oftaking soil profile samples and onsite visits and mapping analyzes in Arc-GIS. The results ofthe work’s own research are as follows: Youth playing soccer in an indoor hall with EPDM granules experience discomfortsuch as itching of the body and poor air quality. The majority of the adult players who answered the questionnaire do not experienceany discomfort when playing soccer on artificial turfs fields. The majority of the surveyed municipalities have not received any complaints regardingartificial turf fields (regarding human health and the surrounding environment). Artificial turf fields do not cause any negative impact on the surrounding infrastructuresuch as the storm water system. At the onsite visit the majority of the artificial turf fields had substantial amounts ofgranules spread out around the fields, both on hard surfaces, in and around stormwater inlet and on the grass and gravel covered areas. In the soil profile samples at one of the artificial turf fields, granulate was found atdepths down to 10 cm. An artificial turf field is considered worn out after 8-10 years. After that time, dependingon the fields condition, it will be reused at other areas or energy recoveredby combustion / Idag är det många kommuner och idrottsföreningar som anlägger konstgräsplaner då de blandannat har en längre utnyttjandetid och ett mindre skötselbehov än naturgräsplaner. Det somkan vara problematiskt med konstgräsplaner är gummigranulatet som används som fyllningi planen. Dessa granulat kan bestå av återvunna däck, vilka kan innehålla för människorshälsa och miljö, skadliga ämnen. Detta var skälet till att Kemikalieinspektionen (KEMI) lätgöra en lägesrapport år 2006 som bland annat kom fram till att miljö- och hälsoriskerna medkonstgräsplaner fyllda med gummigranulat från återvunna däck var små, men att det fannsen lokal miljörisk.Syftet och målet med examensarbetet var att utföra en förenklad riskbedömning över konstgräsplanernai Västerås stad. Riskbedömningen ska kartlägga hur konstgräsplanernas granulatkan påverka recipienter i närheten av planerna, både i dess funktion samt risk för skadapå akvatiska och terrestra ekosystem, men även för människors hälsa. Detta för att ge underlagför att långsiktigt minska spridningen av metaller och miljögifter med syfte att undvikanegativa effekter både på människors hälsa och omgivande miljö.Arbetet delades upp i tre delar, där de två första delarna bland annat redovisar hur en konstgräsplanär uppbyggd, vilka miljö- och hälsoskadliga ämnen som finns i materialet samt engenomgång av miljö- och hälsoriskbedömningar från litteraturen. Den tredje delen är resultatfrån egna undersökningar samt en övergripande riskbedömning av konstgräsplaner i Västerås.Arbetets egen undersökning bestod av två delar. En kartläggande del där frågeformulärskickades ut till ett stratifierat urval av respondenter samt en del bestående av jordprovtagning,platsbesök och kartanalyser.Resultatet av arbetets egna undersökningar är följande: Aktiva ungdomar som spelar fotboll i en inomhushall med EPDM-granulat kännerav besvär såsom klåda på kroppen och dålig luft. Av de vuxna spelarna som besvaradeenkäten uppger majoriteten att de inte känner av några besvär. Majoriteten av tillfrågade kommuner har inte har fått in några klagomål gällandekonstgräsplaner, varken gällande hälsa eller miljö. Konstgräsplaner ger inte upphov till någon negativ påverkan på omkringliggandeinfrastruktur såsom dagvattenbrunnar. Vid platsbesök låg det vid vissa av konstgräsplanerna ansenliga mängder granulatutanför planerna, både på hårdgjorda ytor, i och vid dagvattenbrunnar samt på gräsochgrustäcka områden. Vid jordprofilsprovtagning vid sidan av en konstgräsplan återfanns granulat på ettdjup på ner till 10 cm. En konstgräsplan anses uttjänt efter 8-10 år. Efter den tiden, beroende på planensskick, återanvänds den på andra ytor och när den anses vara helt uttjänt energiåtervinnsden genom förbränning.

Anammox (anaerobic ammonium oxidation) process is a one-step conversion of ammonia into nitrogen gas with nitrite as an electron acceptor. It has been developed as a sustainable technology for ammonia removal from wastewater in the last decade. For wastewater treatment, anammox biomass was widely developed as microbial aggregate where the conditions for enrichment of anammox community must be delicately controlled and growth of other bacteria especially NOB should be suppressed to enhance nitrogen removal efficiency. Little is known about the distribution of microbial aggregates in anammox process. Thus the objective of our study was to assess whether segregation of biomass occurs in granular anammox system. In this study, a laboratory-scale sequential batch reactor (SBR) was successfully operated for a period of 80 days with granular anammox biomass. Temporal and spatial distribution of microbial aggregates was studied by particle characterization system and the distribution of functional microbial communities was studied with qPCR and 16s rRNA amplicon pyrosequencing. Our study revealed the spatial and temporal distribution of biomass aggregates based on their sizes and density. Granules (>200 μm) preferentially accumulated in the bottom of the reactor while floccules (30-200 μm) were relatively rich at the top layer. The average density of aggregate was higher at the bottom than the density of those at the top layer. Degranulation caused by lack of hydrodynamic shear force in the top layer was considered responsible for this phenomenon. NOB was relatively rich in the top layer while percentage of anammox population was higher at the bottom, and anammox bacteria population gradually increased over a period of time. NOB growth was supposed to be associated with the increase of floccules based on the concurrent occurrence. Thus, segregation of biomass can be utilized to develop an effective strategy to enrich anammox and wash out NOB by shortening the settling time and withdrawing floccular biomass from the top of the reactor.

Neste estudo foram sintetizados copolímeros de butadieno e estireno (SBR) através do processo de polimerização em emulsão a quente. Foi avaliada a influência das condições reacionais sobre as principais propriedades dos copolímeros, como grau de encolhimento no moinho, massas molares numérica média (Mn) e ponderal média (Mw), distribuição de massa molar (Mw/Mn) e propriedades reológicas das diferentes SBRs. Os copolímeros obtidos foram avaliados quanto aos módulos elástico (G) e viscoso (G) e tangente delta pelo equipamento Analisador de Processamento de Borracha (RPA) e pelo viscosímetro Mooney MV 2000. Foi verificado no copolímero obtido a influência da adição do agente de reticulação, em que pequena variação da quantidade adicionada do mesmo ao sistema de polimerização, proporcionou grande alteração nas propriedades do copolímero. Os copolímeros obtidos a diferentes conversões da reação de polimerização apresentaram aumento da viscosidade Mooney e massas molares numérica e ponderal médias com o aumento da conversão. A avaliação reológica pelo equipamento RPA de copolímeros comerciais confirmou os resultados obtidos pelo viscosímetro Mooney MV 2000 no teste de relaxação de tensão / In this study copolymers of butadiene and styrene were synthesized by a hot emulsion polymerization process. The influence of the reaction conditions was evaluated on the main properties of the copolymers, as degree of shrinkage in the mill, number (Mn) and weight-average (Mw) molecular weight, molecular weight distribution (Mw/Mn) and the rheological properties of the copolymers. The copolymers were evaluated by the elastic (G) and viscous (G) modulus and tan delta by the Rubber Process Analyser (RPA) and Mooney viscosimeter MV 2000. It was verified that the addition of small quantities of crosslinking agent in the copolymer has a higher influence on its properties. The Mooney viscosity and the number and weight-average molecular weight increased as polymerization conversion increased. The rheological evaluation by the RPA of several commercial copolymers has confirmed the results obtained by the Mooney viscosimeter MV 2000 during the stress relaxation test

Neste estudo foram sintetizados copolímeros de butadieno e estireno (SBR) através do processo de polimerização em emulsão a quente. Foi avaliada a influência das condições reacionais sobre as principais propriedades dos copolímeros, como grau de encolhimento no moinho, massas molares numérica média (Mn) e ponderal média (Mw), distribuição de massa molar (Mw/Mn) e propriedades reológicas das diferentes SBRs. Os copolímeros obtidos foram avaliados quanto aos módulos elástico (G) e viscoso (G) e tangente delta pelo equipamento Analisador de Processamento de Borracha (RPA) e pelo viscosímetro Mooney MV 2000. Foi verificado no copolímero obtido a influência da adição do agente de reticulação, em que pequena variação da quantidade adicionada do mesmo ao sistema de polimerização, proporcionou grande alteração nas propriedades do copolímero. Os copolímeros obtidos a diferentes conversões da reação de polimerização apresentaram aumento da viscosidade Mooney e massas molares numérica e ponderal médias com o aumento da conversão. A avaliação reológica pelo equipamento RPA de copolímeros comerciais confirmou os resultados obtidos pelo viscosímetro Mooney MV 2000 no teste de relaxação de tensão / In this study copolymers of butadiene and styrene were synthesized by a hot emulsion polymerization process. The influence of the reaction conditions was evaluated on the main properties of the copolymers, as degree of shrinkage in the mill, number (Mn) and weight-average (Mw) molecular weight, molecular weight distribution (Mw/Mn) and the rheological properties of the copolymers. The copolymers were evaluated by the elastic (G) and viscous (G) modulus and tan delta by the Rubber Process Analyser (RPA) and Mooney viscosimeter MV 2000. It was verified that the addition of small quantities of crosslinking agent in the copolymer has a higher influence on its properties. The Mooney viscosity and the number and weight-average molecular weight increased as polymerization conversion increased. The rheological evaluation by the RPA of several commercial copolymers has confirmed the results obtained by the Mooney viscosimeter MV 2000 during the stress relaxation test

To reduce energy consumption, and to achieve the desired denitrification, the activated sludge process sometimes needs to operate at low dissolved oxygen concentrations. The ASM2d model describes the activated sludge process, if nitrification and denitrification occur during different phases in a sequencing batch reactor (SBR). Despite the widespread study of enhanced biological phosphorous removal, comprehensive sludge floc distribution model remains lacking that would better describe this process. Consequently, the integrated system model has been developed to understand the impact of floc at low DO concentrations, and during the process of biological nitrogen and phosphorous removal. In a wastewater treatment plant used in this study, the dissolved oxygen was controlled at a low concentration, 1.7〖gO_2 m〗^(-3), and the dispersion coefficient into the floc was found to be 〖D=1.2×10〗^(-4) m^2/day. Introduction of a number of effectiveness factors contributed to the development of the ASM2d model described herein. This developed model could be valuable for predicting process behaviours applicable under various configurations. Moreover, parameters and effectiveness factors for the model could be calibrated using a genetic algorithm approach. Optimisation was then achieved by controlling the solids retention time during the activated sludge process.

Τα τελευταία χρόνια, τόσο σε παγκόσμιο επίπεδο αλλά κυρίως σε Ευρωπαϊκό, παρατηρείται μια προσπάθεια για θέσπιση διαρκώς αυστηρότερων νόμων και διατάξεων που αφορούν την πολιτική περιβάλλοντος, αντικατοπτρίζοντας την αυξημένη οικολογική συνείδηση του συνόλου των πολιτών. Παράλληλα, αναζητούνται μέθοδοι και τεχνικές προκειμένου σε όλους τους τομείς δραστηριότητας των ανθρώπων να επιτυγχάνεται περιορισμός της ρύπανσης. Μέσα σε αυτό το γενικότερο πλαίσιο διαχείρισης, ιδιαίτερη σημασία έχουν τα έργα αποχέτευσης και επεξεργασίας αποβλήτων, που ως σκοπό έχουν την όσο το δυνατόν γρηγορότερη και οικονομικότερη απομάκρυνση των ακάθαρτων και βλαβερών για το περιβάλλον νερών (απόβλητα), καθώς και την κατάλληλη επεξεργασία (καθαρισμό τους), ώστε να διατεθούν ακίνδυνα στο περιβάλλον (Αραβώσης et al, 2003). Σκοποί της διαδικασίας επεξεργασίας λυμάτων είναι η απομάκρυνση των αιωρούμενων σωματίων, της οργανικής ύλης, των μικροβιακών οργανισμών και της τροφικής τους αλυσίδας, αφήνοντας τα υγρά που απομένουν κατάλληλα για απορρόφηση από το έδαφος ή τη διάθεσή τους σε ποτάμια ή στη θάλασσα. Οι τρεις βασικές στάθμες της διαδικασίας επεξεργασίας λυμάτων χαρακτηρίζονται ως πρωτοβάθμια, δευτεροβάθμια και τριτοβάθμια. Κατά την πρωτοβάθμια επεξεργασία πρέπει να απομακρύνονται περίπου τα δυο τρίτα των αιωρούμενων σωματίων και το ένα τρίτο της οργανικής ύλης. Στη δευτεροβάθμια επεξεργασία σε δοχεία ή επιφάνειες αερισμού γίνεται αποδόμηση των μικροοργανισμών που μεταλλάσσονται σε οργανική ύλη. Στο πέρας της χρησιμοποιείται πολλές φορές χλώριο ή ενώσεις του για την απομάκρυνση των επιβλαβών μικροβίων. Αυτή είναι η τριτοβάθμια επεξεργασία, που απαιτείται μόνο όταν πρέπει τα επεξεργασμένα λύματα να χυθούν σε περιβαλλοντολογικά ευαίσθητη υγρή όδευση, οπότε απομακρύνονται οι θρεπτικές ουσίες, όπως αζωτούχες και φωσφορούχες ενώσεις που διευκολύνουν την ανάπτυξη βακτηρίων, μικροβιακών ή άλλων οργανισμών. Πρέπει να τονιστεί ότι οι τρεις αυτές διαδικασίες δεν είναι ποτέ πλήρως διαχωρισμένες και γενικά εξαρτώνται από το σύστημα επεξεργασίας λυμάτων και τις απαιτήσεις αποδόμησής τους. Οι υποχρεώσεις των μηχανικών, των ιδιοκτητών και των ενοίκων που ισχύουν για τις κεντρικές αποχετεύσεις κτιρίων ή οικισμών περιλαμβάνονται σε σχετική Υγειονομική Διάταξη (Aπ. E1β/221 της 22.1/ 24.2.1965 ΦEK 138B) ή αναφέρονται στο Γ.O.K., στον Kτιριοδομικό Kανονισμό και στην T.O.T.E.E. 2412/ 86. Προϋπόθεση για την κατασκευή ιδιωτικού συστήματος συλλογής, επεξεργασίας και διάθεσης των υγρών αποβλήτων είναι η έκδοση άδειας από την αρμόδια αρχή. H προστασία του περιβάλλοντος, του υπόγειου υδροφόρου ορίζοντα και των θαλασσών επιβάλλει την αποφυγή διάθεσης λυμάτων κατά τρόπο που να προξενεί μόλυνση στο υδατικό απόθεμα της γης. Είναι έτσι αναγκαίο σε κάθε περίπτωση που δεν έχει εξασφαλιστεί κεντρικό δίκτυο αποχέτευσης να λαμβάνονται μέτρα διάθεσης των λυμάτων με κατασκευές που γίνονται με δαπάνη των κατασκευαστών των κτιρίων ή των οικισμών ώστε να εξασφαλίζεται διάθεση των λυμάτων κατά τρόπο που να μην επηρεάζεται δυσμενώς το περιβάλλον. Η νομοθεσία η σχετική με τη διάθεση των λυμάτων κτιρίων σε περιοχές χωρίς κεντρικό δίκτυο αποχέτευσης επιβάλλει την υποβολή μελέτης επεξεργασίας και διάθεσής τους (Τσίγκας, 2003) Τα τελευταία χρόνια, προκειμένου να ελεγχθεί η ρύπανση και να αποφευχθεί η περαιτέρω υποβάθμιση των υδατικών πόρων του πλανήτη, έχουν θεσπιστεί ειδικές νομοθετικές διατάξεις, που αφορούν στη βιολογική διεργασία των υγρών αποβλήτων πριν αυτά διατεθούν στους υδάτινους αποδέκτες. Έτσι η βιολογική απομάκρυνση τόσο του οργανικού φορτίου όσο και των θρεπτικών συστατικών (κυρίως αζώτου και φωσφόρου) έχει καταστεί πλέον επιτακτική. Οι διεργασίες βιολογικής απομάκρυνσης του αζώτου μέσω της νιτροποίησης και της απονιτροποίησης βρίσκουν σήμερα ευρεία εφαρμογή στην επεξεργασία τόσο των αστικών και των βιομηχανικών υγρών αποβλήτων όσο και στην προεπεξεργασία του πόσιμου νερού. Η νιτροποίηση (βιολογική οξείδωση της αμμωνίας) υλοποιείται από δύο διαφορετικές κατηγορίες αυτότροφων βακτηριών. Η πρώτη ομάδα (νιτρωδοποιητές) μετατρέπει την αμμωνία (NH+4 ) σε νιτρώδη(NO−2 ) και στη συνέχεια η δεύτερη ομάδα, οι νιτρικοποιητές, οξειδώνει περαιτέρω το ενδιάμεσο προϊόν (νιτρώδη) σε νιτρικά (NO − 3 ). Η απονιτροποίηση είναι η βιολογική διεργασία, η οποία ευθύνεται για την απομάκρυνση του αζώτου με τη μορφή τωννιτρικών και/ή νιτρωδών από τα απόβλητα μέσω της μετατροπής τους σε αέριο άζωτο. Τα τελευταία χρόνια, γίνεται σημαντική ερευνητική προσπάθεια για να παρακαμφθεί το στάδιο της νιτρικοποίησης. Είναι επιθυμητό η αμμωνία να οξειδώνεται σε νιτρώδη και μετά απευθείας να λαμβάνει χώρα η απονιτροποίηση, παρά να γίνεται πρώτα η μετατροπή σε νιτρικά στα συστήματα απομάκρυνσης αζώτου. Θεωρητικά εξοικονομείται περίπου 25% σε δέκτη ηλεκτρονίων (οξυγόνο) και 40% σε δότη ηλεκτρονίων, ενώ επίσης ο ρυθμός απονιτροποίησης αυξάνεται κατά 63% με μικρότερη παραγωγή βιομάζας, οφέλη ιδιαίτερα σημαντικά από οικονομικής πλευράς, καθώς μειώνεται αρκετά το κόστος λειτουργίας της μονάδας επεξεργασίας αποβλήτων. Η παράκαμψη αυτή συνήθως επιτυγχάνεται ρυθμίζοντας κατάλληλα τη συγκέντρωση του διαλυμένου οξυγόνου, το pH και τη θερμοκρασία. Ο σκοπός της παρούσας εργασίας ήταν η εύρεση του βέλτιστου τρόπου λειτουργίας αντιδραστήρα SBR μέσω σχεδιαστικών και λειτουργικών διαφοροποιήσεων με σκοπό την απομάκρυνση του αζώτου από τα λύματα με παράκαμψη της παραγωγής των νιτρικών. Έγινε χρήση των κατάλληλων ρυθμίσεων του πλήθους και της διάρκειας των αερόβιων και ανοξικών φάσεων λειτουργίας του αντιδραστήρα σύμφωνα με την προηγούμενη γνώση που είχαμε αποκτήσει από την εμπειρία του εργαστηρίου πάνω σε αυτή την τεχνολογία και την πατέντα που έχει εξελίχθη στο εργαστήριο μας. Έτσι έγινε περαιτέρω εξέλιξη της πιλοτικής μονάδας που είχε εγκατασταθεί στο χώρο του Βιολογικού Καθαρισμού της πόλεως της Πάτρα σε μεγαλύτερη κλίμακα και σε πραγματικές συνθήκες μεταβολής οργανικής φόρτισης. Κατά την διάρκεια της παρούσας εργασίας έγινε σχεδιασμός και κατασκευή τριών διαφορετικών μονάδων επεξεργασίας λυμάτων τύπου SBR. / In recent years, both at the global level but mainly European, there is an attempt to introduce successively more stringent laws and provisions relating to environmental policy, reflecting the increased environmental awareness of all citizens. At the same time, methods and techniques in order sought in all areas activity of people to achieve the reduction of pollution. within this overall management framework, particular importance are the works sewage and waste treatment, which are designed as long as possible faster and economical removal of dirty and harmful for the water environment (wastes) and the appropriate treatment (purification them) so disposed harmless to the environment (Aravossis et al, 2003). Causes of wastewater treatment process is to remove suspended particles, organic matter, microbial organisms and the food chain, leaving the remaining liquids suitable for absorption from the soil or disposal in rivers or the sea. the three basic levels of wastewater treatment process characterized as primary, secondary and tertiary. In primary treatment must be removed about two thirds of suspended particles and a third organic matter. In secondary processing in containers or Ventilation surfaces becomes degradation of the microorganisms mutated in organic matter. At the end of the used several times or chlorine compounds for the removal of harmful microbes.