Abstract
For many wastewater treatment plants (WWTPs), side-stream treatment of reject water from digested sludge dewatering is a feasible opportunity to improve N-removal efficiency without costly plant expansion. Biological nitrogen removal over nitrite or combined partial nitritation (PN)-Anammox process has recently become a popular treatment method for such ammonium-rich streams. Shortcut nitrification and PN start-ups were successfully performed in a pilot-scale SBR treating real reject water. In all performed experiments, effective nitrate production inhibition occurred in less than 20 days due to operational conditions selection and without advanced control system. pH adjustment in the PN reactor allowed to achieve NO 2 -N /NH 4 -N ratio suitable for Anammox process (1.24±0.07).
Highlights
High quality standards for wastewater treatment plant (WWTP) effluent induce constant development of new technologies, especially considering biological nutrient removal (BNR)
Specific characteristics of this medium, such as high ammonium concentration and temperature, create a convenient opportunity to avoid further nitrite oxidation in the second stage of nitrification by selective NOB (Nitrite Oxidizing Bacteria) inhibition. Such approach can be described as shortcut nitrification if the main goal is to oxidize whole ammonium load into nitrite. Main advantages of this process are: reduction of specific cost of 1g NH4-N oxidation due to lower oxygen consumption, less organic carbon required in further denitrification if such occurs later (i.e. SHARON process) [2], production of nitrite-rich medium that can be a useful source of free nitrous acid (FNA) [3] and activated sludge production enriched with AOB (Ammonia Oxidizing Bacteria) for mainstream bioaugmentation purposes [4]
Shortcut nitrification/partial nitritation (PN) start-up strategy based on simple control of operational conditions in the reactor has proven to be successful and allows to obtain stable NOB activity suppression within two weeks
Summary
High quality standards for wastewater treatment plant (WWTP) effluent induce constant development of new technologies, especially considering biological nutrient removal (BNR). Researcher’s attention attracted alternative technologies for nitrogen removal, especially connected with treating high-strength ammonium streams (i.e. reject water from sludge dewatering), named as side-stream treatment [1] Specific characteristics of this medium, such as high ammonium concentration and temperature, create a convenient opportunity to avoid further nitrite oxidation in the second stage of nitrification by selective NOB (Nitrite Oxidizing Bacteria) inhibition. Despite only slight difference in the amount of ammonium load oxidized, it seems to be important to distinguish a specific type of shortcut nitrification – partial nitritation (PN) used as a necessary pre-treatment preceding Anammox process In this case the main goal is to oxidize part of the ammonium load, achieving NO2-N/NH4-N ratio in the effluent around 1.32, reported as stoichiometric in Anammox reaction [5]
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