TY - JOUR
T1 - Dynamics of nitrate and nitrite in saturated sand filters with enhanced substrate conditions for denitrifying bacteria
AU - Al-Saedi, Rasha
AU - Smettem, Keith
AU - Stefanova, Katia
AU - Siddique, Kadambot H.M.
PY - 2021/2
Y1 - 2021/2
N2 - Substrate conditions for denitrifying bacteria were enhanced by adding carbon sources to a laboratory-scale sand filter system. Temperature, oxidation–reduction potential, and hydrogen ion concentration were measured through the recirculation of nitrogen-dosed wastewater and carbon sources that were mixed to encourage microbial growth, with denitrifying bacteria identified by standard plate counts. Two different external carbon sources (sucrose and ethanol) were added, with and without activated sludge amendments. Nitrate, nitrite, and chemical oxygen demand (COD) concentrations were monitored relative to an untreated control and a treatment with activated sludge under an initial hydraulic loading rate of 0.508 m3 /m2 d and a hydraulic retention time of 2.5 h. Nitrate decay rates were only significantly enhanced for the ethanol treatment without addition of activated sludge. Nitrite initially accumulated when carbon sources were added, but no accumulation was evident by the end of the experiment after 150 min. COD declined when carbon sources were added, but activated sludge had no effect on the rate at which the COD declined. The increased rate of nitrate removal with the addition of ethanol is of technical interest, as the volume of waste-water treated in a unit volume of filter medium for denitrification doubled with ethanol compared with sucrose at the same concentration.
AB - Substrate conditions for denitrifying bacteria were enhanced by adding carbon sources to a laboratory-scale sand filter system. Temperature, oxidation–reduction potential, and hydrogen ion concentration were measured through the recirculation of nitrogen-dosed wastewater and carbon sources that were mixed to encourage microbial growth, with denitrifying bacteria identified by standard plate counts. Two different external carbon sources (sucrose and ethanol) were added, with and without activated sludge amendments. Nitrate, nitrite, and chemical oxygen demand (COD) concentrations were monitored relative to an untreated control and a treatment with activated sludge under an initial hydraulic loading rate of 0.508 m3 /m2 d and a hydraulic retention time of 2.5 h. Nitrate decay rates were only significantly enhanced for the ethanol treatment without addition of activated sludge. Nitrite initially accumulated when carbon sources were added, but no accumulation was evident by the end of the experiment after 150 min. COD declined when carbon sources were added, but activated sludge had no effect on the rate at which the COD declined. The increased rate of nitrate removal with the addition of ethanol is of technical interest, as the volume of waste-water treated in a unit volume of filter medium for denitrification doubled with ethanol compared with sucrose at the same concentration.
KW - Chemical oxygen demand
KW - Denitrification
KW - Nitrate
KW - Nitrite
KW - Saturated sand filters
UR - http://www.scopus.com/inward/record.url?scp=85100800536&partnerID=8YFLogxK
U2 - 10.5004/dwt.2021.26623
DO - 10.5004/dwt.2021.26623
M3 - Article
AN - SCOPUS:85100800536
SN - 1944-3994
VL - 212
SP - 51
EP - 60
JO - Desalination and Water Treatment
JF - Desalination and Water Treatment
ER -