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Degradation of oxytetracycline antibiotic from waste activated sludge by fenton oxidation process
Antibiotics are emerging organic contaminants that enter wastewater network as consequence of human activities, and transferred to sewage sludge by sorption during wastewater treatment. The treatment of antibiotics in waste activated sludge (WAS) deserves special attention since antibiotics have potential to cause the spreading of antibiotic resistant bacterial pathogens in contrast to other emerging organic contaminants.Although Fenton oxidation has been considered as a promising pre-treatment method by providing sludge disintegration and degradation of recalcitrant compounds, there is a lack for the determination of antibiotics? fate during Fenton oxidation of WAS.The efficiencies of Fenton and Fenton-like oxidation for oxytetracycline (OTC) antibiotic, which exhibits high sorption capacity, were evaluated in synthetically contaminated WAS at different experimental conditions. While increased H2O2 dosage and [Fe+2]/[H2O2] ratio affected process efficiency positively, higher total solid content of WAS drastically reduced the OTC degradation. Fenton and Fenton-like oxidations provided 94 % and 87% OTC degradation with 150 g/kg TS H2O2 and 1.2 Fe/H2O2 molar ratio in 120 minutes treatment time, respectively. Metal and nutrient release and enhanced physical properties were additional results of the Fenton oxidation.
Investigation of waste stabilization potential of a medium aged solid waste in a biorector landfill
The production of solid waste is an inevitable consequence of human life. The tremendous increase in the solid waste generation makes the use of landfills, especially bioreactor landfills imminent. Research has shown that municipal solid waste can be rapidly degraded by enhancing and controlling the moisture within the landfill under aerobic and/or anaerobic conditions. Some studies indicate that bioreactors increase the feasibility for cost effective LFG recovery, which in turn would reduce fugitive emissions. This presents an opportunity for beneficial reuse of bioreactors in energy recovery projects. The most common method of creating a land ll bioreactor is the recirculation of leachate, which enhances the degradation of waste.The objective of this study is to evaluate the waste degradation mechanisms of the stabilized waste applying Retrofit Bioreactor Concept. Determination of the further stabilization potential of stabilized solid waste is important for the development of the rehabilitation strategies. Moreover, the study using stabilized refuse provides better understanding of the rehabilitation of traditional landfills and the conversion of existing conventional landfills to operate as a bioreactor concept.
Evaluation of biogas production as a source of renewable energy through co-digestion of agricultural residues and poultry manure
The need for alternative energy sources for Turkey is obvious. Biogas production via agricultural residues and manure seems to be an advantageous option for Turkey, since the main income is generally provided from the agro industry. Through anaerobic digestion of agricultural residues and poultry manure, wastes will be properly disposed and biogas, which is a clean and sustainable source of energy, will be continuously recovered. As a renewable energy source, biogas production from agro industrial wastes is a useful management option, energy independent and environmentally friendly. Biogas can be usedfor production of heat, electricity, as fuel in vehicles and as a substitute of natural gas.The objective of this study was to investigate the potential of biogas generation via anaerobic co-digestion of the chosen agricultural residue -sunflower residues- and poultrymanure. Mixtures composed of different amounts of substrates were prepared and digested under anaerobic conditions with the addition of inoculum culture (seed sludge), using batch tests under mesophilic laboratory conditions.If the potential of biogas production from co-digestion of poultry manure and agricultural residue can be determined by batch-tests, then it will be possible to calculate the theoretical amount of energy that can be produced from these substrates, since the production amounts of agricultural residue and manure are known. According to the results obtained, it will be possible to use these substrates for the continuous lab scale studies or larger scale commercial agricultural biogas plants.Within the scope of this study, several compositions of sunflower residue, poultrymanure and inoculum mixtures were elaborated and digested under mesophilic conditions. However reliable methane production could be only achieved in the first two trials. This outcome is mainly attributed to the low biodegradability of the sunflower residues thus further studies, including pretreatment methods are recommended.
Production of biogas through anaerobic co-digestion of ice cream plant wastewater and ice cream production residue
The primary objective of this study is to determine whether it is possible to dispose of ice-cream production residue (off-spec) and ice-cream wastewater together and to recover energy by anaerobic co-digestion process. Mesophilic batch anaerobic digestion tests were performed under laboratory conditions to evaluate production of methane (CH4) from these substrates. It was found out that it was possible to obtain a high methane yield of 0.338 L CH4 g-1 CODremoved from anaerobic digestion of wastewater alone, with almost 70 % of methane in biogas, while anaerobic digestion of off-spec alone did not seem feasible, due to particular characteristics of the off-spec. When wastewater and off-spec were mixed at a ratio of 9:1 (WW:O) by weight, a methane yield of 0.131 L CH4 g-1 CODremoved could be observed. Lower methane yields for anaerobic co-digestion of wastewater and off-spec could be attributed to high concentrations of sulfate and oil & grease coming from off-spec. Since both ice-cream wastewater and off-spec had variable pH ranges and a poor buffering capacity, adequate amount of buffer must always be present in the anaerobic system to sustain anaerobic degradation.
Life cycle impact assessment of an anaerobic digester plant for organic wastes generated from a university campus in Istanbul
In this thesis, life cycle impact assessment application for the utilization of food wastes through anaerobic digestion (AD) is carried out. For this purpose, characterization of the food wastes generated from selected campuses of Bogazici University is performed as first step. The average biogas potential is found as 0.140 m3/kg wet waste. Around 0.66 m3, 0.70 m3 biogas, 0.36 m3 methane can be obtained per kg of total solid (TS), per kg of volatile solid and per kg of TS, respectively. The integrated AD plant is designed for the university as second stage. During the education period (EP), 55 m3 biogas is generated by AD of ~82 kg of dry waste per day. Nearly 300 kWh energy can be produced by 28 kW cogeneration engine daily. Around 5.5 kWh and 10 kWh energy can be obtained per m3 of biogas and methane, respectively. For the EP, electricity (E) and heat (H) requirements of the plant are determined as 14.95% and 30.53% of the total E and H produced, respectively. The H requirement for the indoor swimming pool at Hisar Campus is designed to be supplied by the AD plant. Roughly, 16% of the H requirement of the pool can be achieved. In the last part of the study; the life cycle assessment (LCA) methodology has been applied. An integrated approach has been brought for AD plant through well known softwares of LCA such as GaBi 4 software. During LCA study, special emphasis is given to global warming (GW). Results showed that, AD technology is highly advantageous over current waste disposal and national energy production systems in terms of environmental protection capacity and renewable energy production. 97.8% reduction and ~85% reduction can be achieved in terms of GW and other relevant categories (acidification, photochemical ozone formation, aquatic eutraphication, terrestrial eutraphication), respectively. When utilization of the produced energy and overall energy requirement of the Hisar Campus is considered, the plant provides 7.23% reduction on GW and more than 4% reduction for other impact categories. Composting is only advantageous when it is considered as a waste management option, since volume reduction is achieved. However, when the energy need of the composting plant is considered, impact of composting scenario is assessed to be higher than other scenarios.
Determination of biogas production potential from various supermarket wastes
Up to date, alternative methods have been investigated to both decrease the environmental effects of wastes and also meet the growing energy demand considering thenew technological developments. Then, biogas production through anaerobic digestion comes forward as an alternative method. Biogas and methane production potential of various substrates and waste sources through anaerobic digestion have been carried out in several laboratory and pilot-scale investigations. Through the continued developments of these investigations and applications, using supermarket wastes in biogas plants occurs as a new method to remove wastes in an environmentally way. The research focused mainly on to investigate the biogas production potential of supermarket wastes. In the concept of research, waste characterizations and suitable total solid (TS, %) ratios of substrates were primarily determined. The objective of this study was to observe the biogas production potentials of every supermarket waste type in the same operation conditions through anaerobic digestion. With this goal, simulated batchreactors were operated in the laboratory at a constant temperature of 350C. Reactors were filled with shredded and homogenized waste mixtures which were collected from waste storage area of one of the supermarket chain. Substrates were prepared considering TS values which were fixed for every reactor. Also, sludge addition was performed in order to accelerate microbial activity before loading to the reactors.Consequently, methane-rich biogas production was observed through anaerobic digestion of supermarket wastes. The better performance in gas production and methane concentration was recorded for mixed wastes due to the better nutritional composition. The feasibility study that was calculated in the light of methane and gas production results showed that installing biogas plant could be feasible in an economically manner for supermarkets.
Assessment and modelling of the toxicity of phenols: A comparative study with marine and freshwater algae
Algae sustain biodiversity in aquatic ecosystems by producing oxygen and recycling nutrients. In contrast to their key role in the environment, toxicity data of many organic pollutants, such as phenols, on algae, especially for marine algae, are severely limited. On the other hand, the data requirement in algal toxicity is almost impossible to be supplied through exhaustive laboratory testing considering the huge number of chemicals to be assessed. Therefore, the use of alternative methods to laboratory testing, such as the quantitative structure-activity/toxicity relationships (QSARs/QSTRs), can help reduce the data gap in algal ecotoxicity.In this study, novel toxicity data of phenols on marine alga Dunaliella tertiolecta and freshwater alga Chlorella vulgaris were generated and subjected to QSAR analysis. The phenols selected for toxicological assessment are known to elicit toxicity through different modes of toxic action including polar narcosis, respiratory uncoupling and reactive mechanisms; as such, the data set was regarded as a miniature model of industrial chemical space and provided a realistic basis upon which to explore the development of algal QSTRs. Multiple linear regression and counter propagation artificial neural network techniques were used to build internally and externally validated QSTR models. Most of the QSTRs highlighted the importance of hydrophobicity and electrophilicity related parameters among numerous descriptors. Hydrophobicity was found to underpin the toxicity of phenols to algae. On the other hand, pyrogallol, hydroquinones and catechols, which are potentially capable of being oxidized to reactive species, displayed algal toxicity in excess of that predicted by hydrophobicity. The toxicity of these reactive phenols was better described by electrophilicity parameters. The external validation of the models was also verified using a data set obtained from literature comprising the toxicity of phenols and anilines to another freshwater alga, Pseudokirchneriella subcapitata. Consequently, the developed QSTRs were shown to be applicable to data from another algal test system and at least for another class of organic compounds.Apart from the QSTRs, investigation of inter-algal and inter-species toxicity correlations between algae and other aquatic organisms such as bacteria, protozoa, daphnia and fish revealed that the response of aquatic organisms to phenols differentiated above the level of polar narcosis. As a result, for a heterogeneous set of compounds acting through different modes of toxic action, the models developed in this study can be used to predict the toxicity of untested compounds provided that the new chemicals are within the applicability domain of the respective model.
Political ecology of small hydraulic power plant constructions in the province of Rize
Hundreds of small hydraulic power plants (SHPPs) in different regions of Turkey have been under construction. However, local people are opposing to these constructions in some regions, especially through judiciary means. The government aims to make legal amendments in order to change the legal basis enjoyed by the opposition until now. These events manifest that SHPPs refer to a case of politicized environment. Relying on a political ecologic perspective, the study defined the issue of SHPPs in Rize as an ecological distribution conflict between different social actors having distinct material interests.To test this hypothesis, this study investigated the state?s policy of SHPPs and the opposition against it, focusing on three valleys in Rize. The research helped to identify the related actors, their motives and strategies. Grassroots actors aimed to defend their livelihood interests that depend on the sustainability of stream ecosystems. Environmental non-governmental organizations supported the cause of grassroots actors from a moral and environmentalist position. The state was driven by a developmentalist and neo-liberal motivation to increase domestic electricity generation capacity by promoting business investments in SHPPs. Although the state is the pivotal actor in this conflict, each actor has its own strengths enabling it to exert power over its opponents.
Impacts of sewage sludge codisposal on waste degredation in aerobic and anaerobic bioreactors
Due to economical, endustrial and technological developments, waste and wastewater sludge productions are increasing gradually all over the world. This situation constitutes to the problem of sustainable solid waste and sludge disposal. Especially diffuculties in finding new landfill spaces, high cost of wastewater sludge management and environmental concerns are forced to find a new method for disposal. Although there are many methods such as incineration, surface disposal and composting, codisposing of wastewater sludge with MSW in the aerobic and anaerobic bioreactors are most used and economical way. Therefore, the objective of this study was to obtain information about sludge codisposal with MSW in the aerobic and anaerobic bioreactors in order to evaluate and determine an efficient and cost-effective landfill management system by utilizing two stage laboratory experiments. These stages include, the lab-scale reactor set-up in order to determine optimum solid waste to sludge ratios by using anaerobic bioreactors and then pilot scale reactor set-up in order to understand the effect of sludge addition on waste stabilization process by using aerobic and anaerobic bioreactors. The results of this study showed that in the lab-scale reactors, codisposal of wastewater sludges with MSW is a very promising method. This method accelerates waste stabilization rates in the anaerobic bioreactors while the energy potential of the sludge is used beneficial. In the pilot scale reactors this study showed that, aeration is a feasible way to treat leachate, fastens stabilization rate and provides rapid removal of organics and nitrogen. On the other hand, CH4 production in the anaerobic was more promising.
Effect of enzymatic pre-treatment on aerobic and anaerobic digestion of wastewater sludges
Aerobic and anaerobic digestion processes aim to degrade the organic matter content of the sludge, remove pathogenic microorganisms from sludge, and produce a stabilized sludge. In the last years, pre-treatment of sludge prior to the digestion process gained more importance due to the potential of increasing sludge solubilization and minimization. This study investigates the effect of enzymatic pre-treatment application prior to the aerobic and anaerobic digestion processes of wastewater sludges. For this purpose, sludge samples were obtained from four different urban and domestic wastewater treatment plants. Digestion tests were carried by operating one control reactor and one enzymatically pre-treated reactor for each sludge sample obtained. An enzyme mixture consisted of alpha-amylase, beta glucanase, lipase, protease, and celllulase was added to the sludge samples 0,5% by volume. The results of the study showed that the enzymatic pre-treatment plays an important role on the performances of the digestion processes. In aerobic digesters, minimization of sludge production was enhanced by the application of enzymatic pre-treatment. Enzyme added reactors showed better TS, VS, MLSS, and MLVSS removals by 43%, 51%, 44%, and 46% reduction in average, compared to the removals of control reactors by 24%, 31%, 28%, and 32% respectively, in average. Enzymes had great impact on the solubilization of large molecular compounds into smaller molecules by the destruction of cell structure. Compared to the control reactors, enzymatically pre-treated reactors showed better performances on the solubilization, which is determined by increased sCOD and DOC concentrations. Enzymatic pre-treatment also affected the release of extracellular polymeric substances from sludge flocs and enzyme addition led to an increase in the protein and carbohydrate contents of sludge. During the digestion process, COD, sCOD, and EPS contents of the sludge samples decreased, where pre-treated reactors showed better removal efficiencies. The dewaterability of sludge samples was deteriorated when they were enzymatically pre-treated at the initial stage. Then, by the aerobic digestion and the degradation of EPS, dewaterability was improved. Similar results were obtained for the anaerobic digesters in terms of sludge minimization and solubilization. In addition, enzymatic pre-treatment prior to the anaerobic digestion resulted in improved biogas production and increased methane potential. In both digestion processes, removal of pathogens was successfully achieved. At the end of the aerobic digestion, the reductions in TC, FC, and FS were about 99,78%, 99,84%, and 99,82%, respectively. At the end of the anaerobic digestion, the reductions in TC, FC, FS, and salmonella were found to be about 99,82%, 99,96%, <99,99%, and 99,98%, respectively. During the study, both urban and domestic wastewater sludge samples were tested but no relationship was found between the source of the sludge and the digestion process.