Biofungus: fungus MBBR pilot plant on Murcia Este WWTP

Abstract

[EN] Concerns about energy efficiency and contaminants of emerging concern (CECs) in wastewater treatment plants (WWTP) lead development of new and alternative processes. Conventional activated sludge systems have a high energy consumption and footprint. Alternative processes are nowadays implemented to reduce them. In this study, we present the results of Biofungus project. Influent wastewater is treated under real conditions and continuous operation in a two-step Moving Bed Biofilm Reactor (MBBR) pilot plant based on Mucor fungus. Several strains and spontaneous mutants of the Mucor fungus were investigated. Those showing improved growth performance, wastewater resistance and nitrate consumption rate were isolated in laboratory and used at the pilot plant. Moreover, the in-situ growth at the pilot plant of the fungus from spores is implemented at the plant as a parallel process. The obtained effluent water meets regulations requirements, showing a high COD and suspended solids (SS) removal (87% and 94% on average respectively) and total nitrogen removal of 35% on average. The Biofungus pilot plant treatment works analogous to a conventional activated sludge process. One of the difficulties observed is the retention of the fungi during the process. The volume of carriers used at the MBBR is between 25-30% of the aeration tank. They allow the fungi to grow attached to them avoiding the dilution of its concentration by flotation and loss from this tank. This stage is followed by a settling tank, where the biomass is either recirculated to the aeration tank or purged to a sludge thickener tank. The process is a two-stage process with aerobic and anoxic reactors. The Mucor fungus specialized in the nitrate consumption is dosed into the anoxic reactor after a different Mucor string has consumed the DQO at the MBBR. Both stages are connected by a primary settling tank and a secondary decanter clarifies water after anoxic stage. After this secondary decanter the treated water is obtained. The retention time on the plant is between 6 and 10 hours and the treated volume is 3,6m3/day. The Mucor fungus has proved able to eliminate high ammonia and nitrate concentrations in sort periods of time, resulting on consumption rates of 1,6 mgN-NO3/h. Finally, its resistance to CECs has been evaluated under a wide range of contaminants including drugs, pesticides, herbicides, fungicides and hormones. Almost no toxicity to contaminant concentrations as high as 20 mg/l was observed. The water treatment performance has been also tested with a combination of CECs at 200µg/l and no influence has been observed after a week over the effluent water quality.