Wastewater from oil refineries is characterized mainly by the presence of hydrocarbons and, in particular, non-ionic volatile organic compounds such as benzene, toluene, ethyl benzene and xylene; lrnown as BTEX, The removal ofBTEX compounds is carried out by commercial activated carbon; however, the widespread use of this adsorbent is limited due to its high cost. As such, alternative novel adsorption techniques using non-conventional low-cost adsorbents are promising methods to remove BTEX compounds, The present study's main focus is to carry out a critical analysis on the removal efficiency of BTEX compounds from aqueous enviromnent in single and multi- component systems, investigate the advantages and limitations of each adsorbent, and evaluate the various adsorption mechanisms. Batch adsorption experiments ofBTEX-contaminated waters (5-200 mg/l) in single component systems were canied out by using chitin and chitosan as adsorbent materials, in order to evaluate the removal performance and to obtain the isotherm profiles. The effects of various parameters such as initial concentrations, adsorbent dose and contact time on the removal performance ofBTEX were investigated. The next part of this work examines the eqUilibrium sorption ofBTEX compounds; in multi-component system, from aqueous solutions by chemically modified chitosan. The enhancement of chitosan was carried out by crosslinking the chitosan with glutaraldehyde, and then grafting the poly(methaclylic acid) onto its backbone. Then, experimental work was carried out to study the adverse effects of major competing ions such as sulfate, phosphate and ammonium ions on the BTEX sorption isotherms and kinetics using chitosan and modified chitosan. The equilibrium data were analysed using Langmuir, Freundlich, RedlichPeterson, Temkin and Dubinin-Radushkevich isotherm models. The linear and non-linear regressions were carried out to determine the best fit model for each system. The linear correlation coefficient was found for each system and the Redlich-Peterson provided the best fit, over the concentration range studied. The non-linear regressions were carried out to evaluate the data by five error analysis methods; namely, the sum of the squares of the errors (ERRSQ), the hybrid fractional error function (HYBRID), Marquardt's percent standard deviation (MPSD), the average relative error (ARE), and the sum of the absolute errors (EABS). Overall, the values of error indicated that the Langmuir isotherm model provided the best quality of fit for the isotherm equilibrium data, for the selected adsorbents. The kinetic studies revealed that the adsorption followed the pseudo-second order rate model for the selected adsorbents, and the pore diffusion is not the only rate controlling step in the removal of BTEX compounds. In terms of added competing ions, it was found that the adsorption behaviour of BTEX compounds was insignificantly affected by the presence of ammonium, phosphate and sulphate ions. The major ions reduced the BTEX adsorption in order of HPO;- > SO;- > NH;J;. This study demonstrated that the chemically enhanced chitosan is a potential adsorbent for the removal of BTEX at concentrations as high as 200 mg/l.

Waste stabilisation pond (WSP) techology has been applied in many countries as a cost effective and sustainable solution to treating wastewater. However, their simplicity of design has been overestimated, which has led to many WSPs under-performing. The main causes for this have been attributed to poor operation and maintenance, adverse environmental conditions and inconect design and loading. This research focuses on how environmental conditions affect the pond and what design changes can be applied to improve the hydraulic perfol1nance despite these factors . The three interventions tested were: a) introduction of longitudinal baffles to create a three channel pond, b) the installation of a stub baffle in front of the inlet to assess the effect of dissipating the energy from the inlet jet, and c) windbreaks to reduce wind access to the pond. These interventions were combined and classified under scenarios to find which gave the best hydraulic perfol1nance. Several tracer studies were carried out for each scenario, which showed good replicability in the hydraulic behaviour despite being canied out at different times of the year. Unlike, the physicochemical parameters for effluent's quality, which showed great variations between seasons, confirming the intricately linked set of biochemical and physical reactions that occur in the pond.Overall, the results indicate that longitudinal baffle (channel) undoubtedly provide better conditions for improved perfol1nance of WSPs and wind can also contribute to an improved performance depending upon surrounding conditions and physical interventions.

Urbanisation has become one of the strongest drivers of growing challenges in the fields of food security, human health and water resources management. Water management is especially more difficult in rapidly growing cities in non-industrialised countries where local authorities typically have insufficient financial and managerial capacities to respond to the basic needs of its citizens. This PhD thesis addresses the research needs for growing cities in non-industrialised countries and their impact on current and future urban water demand, wastewater generation and reuse. It is argued that demographic growth and investments in water supply and sanitation infrastructure are increasingly influencing upstream and downstream water users and the environment in the water basin. Cross-comparative case study methodology was applied, having quantitative and qualitative research components. The qualitative research involved data collection through semi-structured interviews of local experts while the quantitative research consists of data collection from literature and simple urban water balance modelling. The cities of Accra [Ghana], Hyderabad [India] and Addis Ababa [Ethiopia] were selected as case studies. The cities share a number of characteristics typical for the current state of the water system and are detrimental factors for future development. A series of water supply expansion projects were carried out in an effort to keep up with fast rising water demands. Similar investments in sanitation and wastewater disposal, however, were not made, due a lack of priority and indistinct governmental responsibilities. Despite considerable expansion of wastewater treatment to be expected in all cities, the untreated wastewater volume will continue to rise in two cases. Depending on the downstream setting, a considerable fraction of this wastewater is reused in urban agriculture (up to 90%). This has not only brought huge benefits to many farmers but also entailed health risks from exposure to pathogens and environmental degradation. Cities have shifted their use from groundwater to surface water and moved away further from the city to exploit new water sources. However, the latter crucially depends on the financial capacity of the water utility to invest in expansion projects. The presented cases have shown that cities are increasingly influencing the upstream and downstream areas through urban water withdrawal and disposal of wastewater and stormwater. The institutional environment and state of water resources are considered detrimental in the future development of water supply and sanitation in these cities. The combination of tools applied in this research is found to be an appropriate and effective methodology to investigate the urban water balance of fast growing water-stressed cities in developing countries. Urban water balance modelling and scenario development are very suitable tools for local planners and decision makers to adopt and apply in their respective cities.

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Quality control of wastewater is an important treatment process more so now, tnan ever before. Due to an extremely unpredictable nature of the wastewater, which is a mixture of both inorganic and organic waste, it is very difficult to neutralise. Two approaches have been proposed in developing alternative control strategies as suggestions for the pH control of the wastewater in an industrial plant. The first is to develop a mathematical model of a continuously stirred tank reactor (CSTR) with a possible use of MATLAB®. Three different control methods (linear, nonlinear and adaptive) are subject to vigorous theoretical testing and are proposed as a possible solution. The second, a parallel approach, has been to build a laboratory scale experimental reactor using a seven litre continuously stirred tank with monitors for influent flow, influent pH and reactor tank pH. Results suggest that a more sophisticated controller than the simple PID control, currently in operation, could lend Itself to overcoming the problem of persistent large spikes in the pH of the influent. Further work would consider the implementation of these results to the actual industrial wastewater treatment plant.

This study sought to assess the potential of Salicornia europaea (L) agg. to act as biofilter for nitrogen and phosphorus and to determine its suitability as a halophytic replacement for emergent macrophyte species ego Typhus, Juncus in a constructed wetland (CW) for treatment of wastewater produced by a commercially-operating marine fish and shrimp recirculating aquaculture system (RAS). Assessment included, defining an ideal nitrogen concentration for optimum plant growth and nutrient removal; designing and running a pilot scale CW and evaluating its efficiency through quantification of N and P in the influent and effluent and measurement of plant biomass and tissue nitrogen and phosphorus content, with particular attention given to the impact of regular harvests on CW efficiency. Further investigations focussed on the effect of planting on nutrient removal rates, comparing the performance of planted beds to unplanted controls and looking into the effect of planting density on removal rates and yield. Under experimental conditions, at 2 mmol N r', or less, plants had inhibited growth and showed signs of nitrogen deficiency. In contrast, plants grown at 4 and 6 mmol N r' showed signs of an excess of available nitrogen. Treatment nitrogen levels> 2 mmol N r' had little effect on above-ground tissue N content of S. europaea which would indicate that a plants capacity to sequester nitrogen is finite and has to be assessed in relation to its biomass. Application of nitrogen concentrations up to 4 mmol r' would promote production of the most nitrogen rich part of a Salicornia plant, thereby increasing N removal rates and yield of the most commercially valuable part of the plant. When processing fish farm wastewater at ambient concentrations (93 to 439 umol r' TDIN and 34 to 90 umol r' DIP) the pilot-scale constructed wetland planted with S. europaea was highly effective, removing 97 to 100 % TDIN and 41 to 88 % DIP. The addition of ammonium nitrate fertiliser to the fish farm effluent (increasing TDIN loading from 16.9 ± 4.6 mmol m·2 d-I to 139.0 ± 61.2 mmol N m2 d-I) saw CW performance drop to 30 to 58 % TDIN and 19 to 40 % DIP. However, overall assimilation (max. 263 mmol m-2 d-I) of nitrogen by the CW was significantly higher than that reported under ambient N loading. Over the entire 88 day experiment, the CW removed in total 1.28 ± 0.05 mol N m-2 and 0.11 ± 0.01 mol P m-2. Plant uptake accounted for 85% of total N and 73 % of total P removed. The mean nitrogen content in the tissues of the root, shoot and re-growth of S. europaea were all significantly different from each other, 0.61 ± 0.14, 0.80 ± 0.23 and 1.27 ± 0.36 mmol g-I (root, shoot and re-growth respectively), with highest levels measured in the re- growth. A significant 297 DW g m-2 biomass response to addition of inorganic N could be an indication that plant growth was limited by available nitrogen under ambient loading. Croppping was found to reduce CW performance but encouraged production of the succulent tips preferred by the food market whilst removing nitrogen and phosphorus bound in plant tissues from the CW in exchange for an economic return. By comparison, un-cropped had a greater seed yield and uptake potential. When processing fish farm wastewater at ambient TDIN concentrations between 745 to 4087 umol r' the presence of plants within the beds did significantly improve TDIN uptake over the control beds, the removal rates reflected this and the control beds managed 19.9 ± 18.7 mmol m-2 d-I whilst planted beds removed 62.0 ± 25.5 mmol m-2 d-I TDIN over the experimental period. TDIN removal efficiencies ranged between 34 and 73 % for the planted beds and between 0 and 41 % for the unplanted control beds. Planting density had no apparent effect on the rate of TDIN removal. Planted beds produced a yield of 2.6 ±1.1 and 2.2 ± 0.7 FW kg m-2 (high and mid respectively) VI

Endocrine disrupting chemicals such as steroid estrogens and alkylphenol polyethoxylates entering the environment via regular domestic or industrial discharges have been demonstrated to cause feminization of aquatic organisms at trace levels. The presence of these compounds in surface waters has been primarily attributed to their incomplete removal in sewage treatment works and to degradation products generated from alkylphenolic compounds such as alkylphenols and short chain one to three ethoxy units, ethoxylates. This study investigates the factors controlling biodegradation of these chemicals in four sewage treatment works with various configurations of the biological treatment stage. Analytical methodologies for these endocrine disrupting compounds have been developed to allow accurate quantification at nanogram per litre concentrations in sewage matrices. Three activated sludge plants and one trickling filter work were examined. Temperature variation (±10°C) has no impact on the removal of estrogens with the exception of the conjugated estrone-3-sulphate. Removal efficiencies for most of these compounds were >90% at most of these works however the biochemical activity of the biomass was found to be 50-60% more efficient in the nitrifying/denitrifying plant (STW2) compared to the biological nutrient removal plant (STW3). The presence of an anaerobic zone in STW3 did not provide additional benefit in the removal of these compounds compared to a conventional nitrifying/denitrifying plant. The biochemical activity in the nitrifying only pilot-scale plant (STW4) was in between that of the nitrifying/denitrifying plant (STW2) and the biological nutrient removal plant (STW3). It was found that most of the alkylphenols in the final effluents did not exceed and complied with the proposed predicted no effect concentration (PNEC) values of 330 ng l-1 and 122 ng l-1 for nonylphenol and octylphenol respectively. However, concentrations of estrogens at all the works potentially fail to comply with the proposed Environment Agency PNEC value (E2 equivalent = 1 ng l-1).

Οι τυροκομικές μονάδες θεωρούνται παραγωγικές μονάδες έντονου υγειονομικού ενδιαφέροντος, καθώς τα υγρά απόβλητά τους είναι ρύποι υψηλού οργανικού φορτίου και η διαχείρισή τους αποτελεί μείζον περιβαλλοντικό ζήτημα. Υπολογίζεται ότι κατά μέσο όρο, ένα τυροκομείο που επεξεργάζεται 100 τόνους γάλακτος ανά ημέρα, παράγει τυρόγαλα που ρυπαίνει όσο τα απόβλητα μιας πόλης 55.000 κατοίκων (Sienkiewicz, T. & Riedel, C.-L., 1990). Τα απόβλητα του τυροκομείου συνίστανται κυρίως από αραιώσεις γάλακτος, παραπροϊόντα παραγωγής, λιπαντικά, απορρυπαντικά και αστικά λύματα, βασικός ρύπος, όμως, των υγρών αποβλήτων των τυροκομικών μονάδων είναι ο ορρός του γάλακτος. Αν εξαιρέσουμε περιπτώσεις παραγωγής νέων παραπροϊόντων από την περαιτέρω επεξεργασία του, κατά βάση ο ορρός γάλακτος απορρίπτεται χωρίς καμία επεξεργασία σε διάφορους υδάτινους αποδέκτες ή στο δίκτυο της αποχέτευσης, ελοχεύοντας ιδιαίτερους περιβαλλοντικούς κινδύνους. Η επεξεργασία των υγρών αποβλήτων των τυροκομείων και ιδιαιτέρως με βιολογικό τρόπο, είναι ένας περιβαλλοντικός τομέας με ιδιαίτερο ερευνητικό ενδιαφέρον. Η χρήση βιομηχανικής κλίμακας μονάδας βιολογικής επεξεργασίας υγρών αποβλήτων τυροκομείου με αντιδραστήρες σταθερής κλίνης, με ανακυκλοφορία και με φυσικό αερισμό αποδεικνύεται εξαιρετικά αποδοτική, με ελάχιστο πάγιο και λειτουργικό κόστος και χαμηλό ενεργειακό αποτύπωμα. Στόχος της εργασίας αυτής ήταν να καταγραφεί η περιγραφή της συγκεκριμένης μονάδας βιολογικής επεξεργασίας, να θεμελιωθεί θεωρητικά η λειτουργία της και τέλος, να βελτιστοποιηθεί, έτσι ώστε η απόδοσή της να είναι ακόμα πιο ικανοποιητική. / --