Application of biochar for efficient municipal wastewater treatment

Pokharel, Abhishek

Dissertation/Thesis

2020

Farooque, Aitazaz

Farooque, Aitazaz
Peters, Wayne
Zaman, Qamar
Abbey, Lord
Hsiao, Amy

Peters, Wayne
Zaman, Qamar

Master of Science

Sustainable Design Engineering

Sustainable Design Engineering

University of Prince Edward Island

Charlottetown, PE

A more circular and therefore more sustainable economy requires us to value our waste. Something like wastewater can be an unconventional source of nutrients, energy, and water. Thus, far from being something to discard or ignore, wastewater can be a resource option. Similarly, biochar is the solid by-product of pyrolysis and its cascading use can offset the cost of the process. A wide variety of research on biochar has highlighted its ability to absorb/adsorb nutrients, metals, and complex Show moreA more circular and therefore more sustainable economy requires us to value our waste. Something like wastewater can be an unconventional source of nutrients, energy, and water. Thus, far from being something to discard or ignore, wastewater can be a resource option. Similarly, biochar is the solid by-product of pyrolysis and its cascading use can offset the cost of the process. A wide variety of research on biochar has highlighted its ability to absorb/adsorb nutrients, metals, and complex compounds; filter suspended solids; enhance microorganisms’ growth; retain water and nutrients as well as increase carbon content of soil. The thesis analyzes the effect of biochar in two biological treatment processes, activated sludge for municipal wastewater and anaerobic digestion for sludge at Charlottetown Pollution Control Plant located in the province of Prince Edward Island, Canada. The analysis is carried out using Response Surface Methodology for varied size and dose of two types of carbon, namely biochar from wood pallets and non-treated activated carbon (AC) sourced from Sigma Aldrich Inc. A higher COD removal efficiency of above 80%, 82% and 88% in the retention time of 1, 4 and 24 hours respectively is achieved in the region of lower size and higher dose for AC. Whereas, for similar condition and variations the reactor fed with biochar achieved COD removal efficiency of 60, 78 and 69 for hydraulic retention time (HRT) of 1, 4 and 24 hours, respectively. The study showed that the addition of AC and biochar improves the settleability of the sludge. However, the improvement was found to depend on carbon size and dose, irrespective of the carbon type use. A sludge volume index (SVI) as low as 37.33 was obtained with biochar. The response surface analysis showed that minimum SVI could be achieved with small size and higher dose of carbon material. It was also found that the use of carbon in anaerobic digestion has significant effect on the biogas yield and the quality of the biosolids. However, the study can only be a qualitative indication of AC and biochar effect in anaerobic digestion. There are far too many interaction and lurking effects caused due to addition of biochar and AC which in return effects the biogas yield and nutrient content of bio-solids. Moreover, biochar addition was found to be better than AC in anaerobic systems. This study has showed that types of biochar has significant impact on the biological systems in the wastewater treatment process and could be a viable way for valorization of wastewater. In addition, sustainable biochar systems are an attractive approach for carbon sequestration and total waste management cycle. Show less

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