Nitrogen removal from wastewaters by a bio-reactor with partially and fully submerged rotating biofilms

Abstract

This paper concerns simultaneous nitrification and denitrification in a completely mixed bio-reactor with partially and fully submerged rotating biological contactors. The bio-reactor is designed to cause the nitrification and denitrification in partially and fully submerged biofilms, respectively. An experimental investigation was made into the effect of organic material and ratio of influent organic carbon to ammonia nitrogen concentrations(C/N ratio) on the efficiency of simultaneous nitrification and denitrification in the bio-reactor. Settled municipal wastewater and synthetic wastewater containing ammonia nitrogen and organic material such as acetate, ethylene-glycol, phenol and poly-vinyl-alcohol(PVA) were fed into the experimental units. A biofilm dominated by nitrifiers developed on the partially submerged contactors, while a biofilm dominated by heterotrophs developed on the fully submerged contactors. A micro-aerobic environment was formed and biological denitrification occurred in the submerged biofilm. In the municipal wastewater treatment where the influent C/N ratio was around 3.5, the maximum nitrogen removal efficiency was about 60 %. Acetate and ethlene-glycol were effectively used as the organic source of the denitrification. The ability to aerobically degrade PVA was induced by phenol. Once the bacteria inhibiting the biofilm gained the ability to degrade PVA, PVA became an effective organic source of the denitrification.

Rotating biological contactors: a review on main factors affecting performance

“…Wanner et al (1990) described an energy usage of 1.6 kWh/kg of BOD 5 removed in a full-scale RBC packed with cylindrical PVC offcuts. Watanabe et al (1994) referred that the electrical power consumption of the pilot RBC was 0.005 kWh/m 2 d at a rotational speed of 1 rpm.…”

Denitrification in a closed rotating biological contactor: effect of disk submergence

“…For the initial formation and accumulation of biofilm, the reactors were operated in batch mode for a week. After this period, they were fed continuously with a synthetic wastewater: 408 mg/l C 6 2 O. Due to the medium buffering capacity, no pH adjustment was performed.…”

“…These authors also consider that extensive process design information with respect to disk submergence is still not available in the literature. Several studies have employed rotating biological contactors for nitrogen removal [4][5][6][7][8]. However, partially submerged disks are used for nitrification, while completely submerged disks are used for denitrification.…”

Influence of growth manner on nitrifying bacterial communities and nitrification kinetics in three lab-scale bioreactors

“…Biofilm processes are believed to enrich bacteria with relatively long generation times and are considered fit for the growth of bacteria with different oxygen demands, such as aerobic, anoxia, and anaerobic conditions. Biofilm processes also offer a certain degree of simultaneous nitrification and denitrification (SND) [3,4,15,38,39]. The mixed-system pattern can theoretically offer various microenvironments for multiple microorganisms and reduce required reactor volume.…”