title: Effect of shock and mixed loading on the performance of SND based sequencing batch reactors (SBR) degrading nitrophenols.
abstract: The effect of nitrophenolic shock loads on the performance of three lab scale SBRs was studied using a synthetic feed. Nitrophenols were biotransformed by Simultaneous heterotrophic Nitrification and aerobic Denitrification (SND) using a specially designed single sludge biomass containing Thiosphaera pantotropha. Reactors R1, R2 and R3 were fed with 200mg/L concentration of 4-nitrophenol (4-NP), 2,4-dinitrophenol (2,4-DNP), and 2,4,6-trinitrophenol (2,4,6-TNP) whereas reactor R was used as a background control. Three nitrophenolic shock loadings of 400, 600 and 800 mg/Ld were administrated by increasing the influent nitrophenolic concentration while keeping the hydraulic retention time as 48 h. The shocks were given continuously for a period of 4 days before switching back to normal nitrophenolic loading (200mg/Ld). The reactors were allowed to recover to normal performance level before administrating the next nitrophenolic shock load. The study showed that a nitrophenolic shock load, as high as 600 mg/Ld was completely degraded by the 4-NP & 2,4-DNP bioreactors while almost half degraded by the 2,4,6-TNP bioreactor without affecting the reactor's performance irreversibly. After resuming the normal nitrophenolic loading, it took almost 8-10 days for the reactors to recover from the shock effect. The study was further extended to evaluate the maximum possible mixed nitrophenolic loading (4-NP:2,4-DNP:2,4,6-TNP 1:1:1) to which a reactor (R3) containing 2,4,6-TNP acclimated single sludge biomass can be exposed without hampering the reactor performance irreversibly. The reactor was able to achieve pseudo-steady-state at a mixed nitrophenolic loading of 300 mg/Ld with more than 90% removal of all the three nitrophenols, but could remove half of the mixed nitrophenolic loading of 600 mg/Ld.
authors.affiliation: Center for Environmental Science and Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India. pradnyakulkarni@iitb.ac.in
authors.forename: P M
authors.initials: PM
authors.lastname: Kulkarni
mesh_terms: D001673:Biodegradation, Environmental / Q000187:drug effects; D019149:Bioreactors; D058440:Denitrification; D058465:Nitrification; D009596:Nitrophenols / Q000032:analysis / Q000378:metabolism* / Q000494:pharmacology; D042084:Paracoccus pantotrophus / Q000378:metabolism*; D012722:Sewage / Q000382:microbiology*; D014865:Waste Disposal, Fluid / Q000379:methods*; D018508:Water Purification / Q000379:methods*
chemical_list: D009596:Nitrophenols; D012722:Sewage