Simultaneous removal of nutrients in a novel anaerobic–anoxic/aerobic sequencing reactor: removal of nutrients in a novel reactor

Abstract

Discharging wastewater contaminated with nitrogen and phosphorus compounds (nutrients) can be harmful to both human health and the environment. The present study investigated the efficiency of removing total nitrogen, total phosphate, and chemical oxygen demand using a novel reactor design. The reactor was an anaerobic-anoxic/aerobic sequencing batch reactor with continuous influent and discontinuous outlet. The operation consisted of four phases. Phases 3 and 4 had mixing cycles, whereas phases 1 and 2 only had aeration, settling, and discharge cycles. Phase 4 was the most effective. The average removal efficiencies for chemical oxygen demand, NH 4? , total nitrogen, and total phosphate in Phase 4 were 92, 91, 86, and 85 %, respectively. This phase comprised 225 min of intermittent aeration time, 165 min of intermittent mixing time, and 90 min of settling and discharge. In addition to high efficiency in nutrient removal, the reactor had other advantages, including continuous flow and performance in all phases.

Nitrogen removal in domestic wastewater after anaerobic treatment

“…In the 1950s, additional to the organic material removal, nitrification was introduced in the activated sludge process [20] . Conventional N removal comprises two completely different microbial processes: nitrification and denitrification [29] .…”

“…In this second reactor, the demand of organic carbon was often not satisfied because of the high N load and relative low carbon content of the wastewater. To increase the denitrification rates under such conditions, usually readily biodegradable organic compounds like methanol and acetate was added to the second reactor [20,29] . Thus, the treatment system was composed of two reactors with different sludge, the first one being for organic material removal and nitrification; and the second one, for denitrification.…”

“…Thus, the treatment system was composed of two reactors with different sludge, the first one being for organic material removal and nitrification; and the second one, for denitrification. However, it was established soon that the organic material present in the wastewater could be very well used for nitrate reduction [20,29] .…”

“…An important issue is the aeration, which must be adjusted to provide enough dissolved oxygen (DO) for nitrification (3.16 g O 2 g -1 NH 4 + ) but avoiding unnecessary energy consumption. The aeration requirements represent one of the main fractions of the treatment cost in WWTPs performing conventional nitrification/denitrification [20,28,29] . In WWTP it is common to include an anaerobic tank before the anoxic/oxic stages.…”

“…These factors can vary significantly and unpredictably in wastewater and treatment processes, so it is difficult to achieve and maintain high removal via nitrite [27,28,36] . [27,29] . less oxygen demand and 100% savings on an external C source for denitrification, because it is a low-oxygen consuming process [27,28,37] .…”