Integrated carbon dioxide mitigation and nutrient removal from municipal and industrial wastewater using microalgal systems

Download
2017
Kılıç, Gece Cansu
The aim of this master thesis study is to investigate the nutrient removal efficiency from different kinds of wastewaters and the carbon dioxide mitigation in photobioreactors with unialgal culture, Chlorella vulgaris. In the first part of the study, Chlorella vulgaris culture was cultivated in the Bold’s basal medium in batch reactors to increase the biomass content and to observe the growth phases of alga. Then, two parallel photobioreactors (PBRs) were run to cultivate Chlorella vulgaris culture semi-continuously to determine the minimum control requirements on the system to achieve steady-state. pH control at every feeding procedure and temperature regulation requirements became evident. Secondly, nutrient removal from municipal wastewater by Chlorella vulgaris was investigated. Three PBRs were operated at 2, 4 and 8 days of hydraulic retention time (HRT) in semi-continuous PBRs to determine the optimum HRT to achieve the highest nutrient removal. At the 4 day of HRT, 98-100% total ammonium nitrogen (TAN) and 85-98% ortho-phosphate (PO4-P) removal efficiencies were achieved, which was the highest removal among all other HRTs. Before and after the semi-continuous set of experiments, batch sets were run with unacclimated and acclimated algal culture. The highest biomass growth rates of the cultures were measured as 0.39 d-1 for unacclimated and 0.82 d-1 for acclimated culture showing that acclimation is important for system efficiency. At the final part, it was aimed to treat coke factory wastewater, which was mixed with supernatant of primary sludge thickener (thickener supernatant) to provide phosphorus and dilution to the system by supplying 4% carbon dioxide (CO2)-enriched air with Chlorella vulgaris. Mixing ratio of two wastewaters was determined by set of batch experiments to identify the optimum nitrogen: phosphorous (N/P) ratio for Chlorella vulgaris. After this ratio was determined as 6, semi-continuous set of experiments were done with mixed wastewater prepared accordingly. Among 3 HRTs studied (5, 8, and 12 days), 12 days of HRT provided the best removal rates as 97.5% TAN, 97% PO4-P, and 17.7 % CO2 removal. Outcomes of this thesis study can be further used for large scale experimental sets to treat that specific wastewaters with Chlorella vulgaris.

Suggestions

Integrated nutrient removal and biogas production using microalgal and anaerobic microbial cultures
Çalıcıoğlu, Ayşe Özgül; Demirer, Göksel Niyazi; Department of Environmental Engineering (2013)
Following industrialization and urbanization, there have been significant impairments in key nutrient cycles, affecting both ecosystems and human well-being. Urban sewage is rich in nutrients such as nitrogen and phosphorus, which cause eutrophication in receiving water bodies, if not removed. Microalgal nutrient removal is a viable alternative for biological wastewater treatment, considering their high nutrient uptake capabilities of microalgae. These systems are also advantageous in terms of nutrient recy...
Reactivation potential of indicator bacteria in anerobically digested sludges after dewatering processes
Erkan, Müge; Sanin, Faika Dilek; Özdağ, Hilal; Department of Biotechnology (2011)
Anaerobic digestion process which has long been known to successfully reduce the organic content of sludge is one of the most common alternatives to meet pathogen reduction requirements for particular classes of biosolids. However, it has recently been reported that, significantly higher densities of indicator bacteria have been measured in dewatered cake samples compared to samples collected right after anaerobic digestion. In addition, this increase in bacterial population has been commonly observed after...
Investigation of activated sludge bioflocculation : influence of magnesium ions
Turtin, İpek; Sanin, Faika Dilek; Department of Environmental Engineering (2005)
Activated sludge systems are the most widely used biological wastewater treatment processes all over the world. The main working principles of an activated sludge system are the oxidation of biologically degradable wastes by microorganisms and the subsequent separation of the newly formed biomass from the treated effluent. Separation by settling is the most troublesome stage of an activated sludge process. A decrease in the efficiency of the separation of microbial biomass from the treated effluent causes a...
Ozone treatment of excess biological sludge and xenobiotics removal
Muz, Melis; Gökçay, Celal Ferdi; Department of Environmental Engineering (2012)
A novel ozone-assisted aerobic sludge digestion process to stabilize and decrease the amount of excess sludge produced during biological treatment is presented in this study. Excess sludge production is a well known burden for the treatment plants both legally and financially. Moreover, with the arise in the knowledge in recalcitrant compounds it is understood that it can act as a significant secondary pollutant. With the developed pulse ozonation method, waste activated sludge samples from Ankara Tatlar an...
Treatment and valorization of anaerobic digestate
Ülgüdür, Nilüfer; Bayramoğlu, Tuba Hande; Demirer, Göksel Niyazi; Department of Environmental Engineering (2019)
Anaerobic digestion is a widely applied process for the stabilization and treatment of high-strength wastes. The process has two outputs, biogas and digestate. Even though biogas produced during the treatment is a renewable energy source and has positive impacts on improving the economics of the plant, the treatment and disposal of the digestates present a challenge. The treatment methods offered so far are either costly or low yielded which drives off these uneconomic and non-viable treatment processes fro...
Citation Formats
G. C. Kılıç, “Integrated carbon dioxide mitigation and nutrient removal from municipal and industrial wastewater using microalgal systems,” M.S. - Master of Science, Middle East Technical University, 2017.