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PERFORMANCE OF A GRANULAR ACTIVATED CARBON BIOFILTER IN LOW STRENGTH WASTEWATER TREATMENT. D. S. Chaudhary, H. H. Ngo and S. Vigneswaran. E E R D L. Environmental Engineering Group, E. E. R & D Laboratory , Faculty of Engineering,
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PERFORMANCE OF A GRANULAR ACTIVATED CARBON BIOFILTER IN LOW STRENGTH WASTEWATER TREATMENT D. S. Chaudhary, H. H. Ngo and S. Vigneswaran E E R D L Environmental Engineering Group, E. E. R & D Laboratory, Faculty of Engineering, City Campus, Building 2, Level 6, University of Technology, Sydney, P. O. Box 123, Broadway, NSW 2007, Australia
INTRODUCTION • Any conventional filter with attached biomass growth on the filter media is known as BIOFILTER. • Biofilter can be used in both Water and Wastewater Treatment efficiently. • GAC biofilter is often used in tertiary wastewater wastewater treatment and water treatment.
INTRODUCTION Contd…… • Biofilter is the only economical biological treatment option in the tertiary wastewater treatment. • Biofilter is also economical and environmentally friendly solution in treating wastewater of relatively small volume e.g. from hotel or small communities.
INTRODUCTION Contd…… • In tertiary wastewater treatment, biofilter can remove nutrients and dissolved organic substances and produces effluent of high quality for reuse purpose. • In water treatment, it can remove pollutants such as biodegradable and synthetic organic materials that procure odor and taste and cause microbial regrowth in water distribution pipelines.
Materials and Methods • Filter column of diameter 2 cm and height 50 cm was employed • The column had ports for influent feed, effluent collection and backwashing. • The column was packed with 5 g of GAC (bed depth 4 = cm, porosity = 0.65, particle surface area = 1104 m2/g, effective particle size = 0.55 - 0.75 mm)
Schematic Diagram of the experimental Set-up For the Biofilter Constant Head Overhead Tank Influent Feed Overflow Line Port with Valve Backwash Water out Filter Column (dia. 2 cm) Biomass attached on GAC Pellet Valve P Valve Stock Solution of Synthetic Wastewater Stainless Steel Mesh Pump Backwash Water in Effluent out Valve
Material and methods contd.……. • Constant pressure head was maintained to keep a constant filtration rate of 1 m/h. • The filter was backwashed at 30% bed expansion for approximately 5 minutes every 24 hours of filter run. • Total organic carbon (TOC) was measured using UV-persulphate TOC analyser (Dohrmann, Phoenix 8000).
Material and methods contd.…… • Total adsorbed biomass as dry weight was calculated every week. • The synthetic wastewater was prepared everyday and the filtration was run continuously for 77 days.
Results and Discussion • TOC contribution of Glucose, Peptone and Yeast extract with inorganic compounds was 79%, 11% and 10% respectively. • Biodegradation of organic substances suggested that fresh synthetic wastewater solution need to be prepared everyday for filter influent.
Performance of the GAC Biofilter(Average influent TOC = 3.5 mg/L, Bed depth = 4 cm, Filtration rate = 1 m/h)
Biomass Growth in the GAC Biofilter(Average influent TOC = 3.5 mg/L, GAC = 5 g, Filtration rate = 1 m/h)
Results and discussions contd.……. • Minimum biomass of 0.036 g per g of GAC was observed after 63 days of continuous operation. • Another set of operation conducted at 2.5 m/h filtration rate showed a biomass growth of 0.1 g per g of GAC in 30 days. • The decrease in biomass during 7th to 9th week of operation may be due to die-off of microorganisms and its subsequent removal in backwashing
Effect of Filtration Rate on the Performance the GAC Biofilter(Acclimatization period = 77 days, GAC = 5 g, average influent TOC = 3.5 mg/L)
Effect of Influent Organic Concentration on the Performance the GAC Biofilter(Acclimatization period = 77 days, GAC = 5 g, Filtration rate = 1 m/h)
CONCLUSIONS • GAC biofilter can effectively be used to produce better quality of effluent for wastewater reuse purpose. • The biological activity led to consistent organic removal efficiency over a long period of time. • The daily backwash adopted did not seem to affect the biological mass growth thus effluent quality.
Conclusionscontd.…… • Further works on the different concentration and composition of attached biomass are necessary for correct evaluation of the biofilter. • Further works with real wastewater are also necessary for its practical application in the field. • A correct choice of filtration rate and filter bed depth is necessary for long-term operation with consistent and superior effluent quality.