Modeling urea biodegradation in activated sludge using combined respirometric–titrimetric measurements

Abstract

ab s t r ac tUrea biodegradation kinetics determination has been performed in the literature using a two-step nitrification model that was calibrated using on-line respirometric measurements. However, the model neglected the initial hydrolysis step that converts urea to carbon dioxide and ammonia nitrogen, and assumed constant carbon dioxide transfer rate (CTR), though it is inherently a nonlinear process which has an impact on the titrimetric modeling. Hence, in this paper, it is aimed to propose a complete two-step nitrification model for urea biodegradation paying attention to urea degradation pathway along with due consideration given for non-linear CTR process occurring in activated sludge system. Experiments were performed in a simple batch reactor equipped with respirometric and titrimetric set-up. Three different initial urea concentrations were added to the reactor for investigating the process kinetics. Proposed model was successfully calibrated with respirometric, titrimetric and combined respirometric-titrimetric measurements; and the estimated parameters were compared for model evaluation. Furthermore, the proposed model was validated with off-line ammonium, nitrite and nitrate measurements. The study revealed that urea was hydrolyzed at a faster rate in liquid phase. The maximum growth rates of the Nitrosomonas species and the Nitrobacter species were found to be 0.065-0.1 d -1 and 0.006-0.008 d -1 respectively.

Visible-light induced degradation of diphenyl urea and polyethylene using polythiophene decorated CuFe2O4 nanohybrids

“…Likewise, plastic pollution has become a global problem and according to the US EPA (United States Environmental Protection Agency) more than 200 tons of plastic is produced annually 5 . Micro- plastics (MPs) (plastic materials with < 5 nm) that are directly discharged into the environment can build up in the stomach, induce blockage, inflammation in many organs and also produce genotoxicity 6 – 9 . The treatment of urea wastewater via biological 5 , 6 , enzymatic 10 and electrochemical approaches have been attempted by several authors, while very few studies have been carried out on the degradation of plastics, including the bio/photocatalytic degradation of polyethylene polymers by Zalerion maritimum 11 TiO 2 nanotubes 12 , ZnO 13 , N- doped TiO 2 14 , 15 , and Pt/ZnO 16 , 17 .…”

“…Micro-plastics (MPs) (plastic materials with < 5 nm) that are directly discharged into the environment can build up in the stomach, induce blockage, inflammation in many organs and also produce genotoxicity [6][7][8][9] . The treatment of urea wastewater via biological 5,6 , enzymatic 10 and electrochemical approaches have been attempted by several authors, while very few studies have been carried out on the degradation of plastics, including the bio/photocatalytic degradation of polyethylene polymers by Zalerion maritimum 11 TiO 2 nanotubes 12 , ZnO 13 , N-doped TiO 2 14,15 , and Pt/ZnO 16,17 . Lately, the photocatalytic properties of spinel ferrites have been widely reported for oxidative dehydration of hydrocarbons 18 , decomposition of alcohols and hydrogen peroxide 19 , oxidation of carbon monoxide 20 , and degradation of dyes [21][22][23][24][25][26] .…”