Anammox process for cost-effective industrial wastewater treatment
The technological basis of the anammox process is the microbiological process of ammonia oxidation with nitrite under oxygen-free conditions. Since organic substances are not required for this process, Anammox is considered to be one of the most cost-effective technologies for industrial wastewater treatment, where none, or limited organic substances are present. The first anammox process-based technology in Russia has been developed in Moscow.
Since almost 90% of Anammox plants in the world are made in a single-reactor design, this path was chosen. In addition, there was also an unattached active nitrifying sludge in the reactor. Thus, the technology, by the type of used sludge, belongs to the combined type technologies (IFAS - Integrated Fixed / Activated Sludge). An installation was designed and built, the diagram and appearance of which are shown below.
The Anammox bioreactor is designed as a "carousel" reactor, that is, it is a hydraulically mixed reactor - complete mixing and displacement at the same time. Biochemical processes are carried out by two types of sludge: fixed on the feed material (mainly Anammox and nitritation processes take place); free-floating flocculated (processes of nitritation and oxidation of organic matter). Mixing is carried out by submersible mixers from Wilo («Вило Рус», Moscow). Anammox activated sludge biomass is retained on the sheet feed material «Polivom» (NPF ETEK LTD, Kaluga). The temperature in the reactor is maintained at 30–37 ºС, oxygen concentration 0.05–0.2 mg / l, pH 7.5–8.5, nitrite concentration (in terms of nitrogen) no more than 200 mg / l, sludge dose 4–8 g / l. The hydraulic residence time in the bioreactor was 24–48 hours.
The reactor was fully automated, process control and operation were carried out from an automated workstation based on a computer and controllers (developed by NPO «Signal-Electro», Moscow). Standard methods were used to determine the cleaning performance. Two new elements were introduced into the design of the bioreactor, which are not present in any other reactor of the Anammox type - a post-oxidizer reactor, in which the residues of organic matter and ammonium are removed under aerobic conditions, and an activated sludge mill (using a high-speed stirrer for 20–60 s). These devices are necessary to prevent sludge from floating up in the secondary clarifier.
Results and next steps
The unit was fed with the filtrate of centrifuges dehydrating the fermented sludge of the Lyubertsy treatment facilities in Moscow. The data on the composition of the filtrate supplied to the Anammox pilot plant and the composition of the water purified in the installation are presented in table 1.
The plant was inoculated with Anammox activated sludge (500 g dry matter) containing the new Anammox bacteria Sandidatus Jettenia Moscovienalis. The plant has been operating for 2.5 years. The first year of operation was described earlier. At present, the unit operates stably, providing 70–90% nitrogen removal at a water flow rate of 15–20 m3 / day (diagram below). A "failure" in the period of 200-250 days is associated with the experimental technological restart of the installation.
The world-known technologies of Anammox differ in the type of hydraulics (flow / SBR), the type of biomass retention (loading / settling tank / hydrocyclone), if there is a load - its type (floating / attached), according to anammox bacteria (Table 2).
The presented new technology in terms of specific volumetric power corresponds to other Anammox technologies, and in terms of the totality of features it differs from all others (retention of Anammox biofilm on a flat stationary loading, the presence of devices for additional oxidation and crushing of activated sludge, unique anammox bacteria).
Potential applications in the BSR
The proposed design is also applicable to WWTP treatment plants in the BSR.