Digested blackwater treatment in a partial nitritation-anammox reactor under repeated starvation and reactivation periods

Wastewater source-separation and on-site treatment systems face severe problems in wastewater availability. Therefore, the effect of repeated short-term starvation and reactivation periods on a partial nitritation-anammox (PN/AMX) based processes were assessed treating digested blackwater at room temperature. Two sequencing batch reactors (SBR) were operated, one of them during 24 h/day the whole week (SBR-C, which served as control) and the other with repeated starvation/reactivation periods during the nights and the weekends (SBR-D), using simulated blackwater (300 mg N/L and 200 mg COD/L) as substrate. Results showed no remarkable differences in overall processes performance between both reactors, achieving total nitrogen removal efficiencies (NRE) around 90%. Furthermore, no significant variations were measured in specific activities, except for the aerobic heterotrophic one that was lower in SBR-D, presumably due to the exposure to anoxic conditions. Then, the technical feasibility of applying the PN/AMX system to treat real blackwater produced in an office building during working hours was successfully proved in a third reactor (SBR-R), with the same starvation/reactivation periods tested in SBR-D. Despite the low temperature, ranging from 14 to 21 °C, total NRE up to 95% and total nitrogen concentration in the effluent lower than 10 mg N/L were achieved. Moreover, the PN/AMX process performance was immediately recovered after a long starvation period of 15 days (simulating holidays). Results proved for the first time the feasibility and long-term stability (100 days) of applying the PN/AMX processes for the treatment (and potential reuse) of blackwater in a decentralized system where wastewater is not always availableThis work was funded by the Pioneer_STP (PCIN-2015-22 MINECO (AEI)/ID 199 (EU)) project by the WaterWorks2014 Cofunded Call (Water JPI/Horizon 2020) and by MEDRAR (IN852A 2016) project by the Galician Government. The work of G. Tocco was financially supported by the University of Cagliari (Italy) and by European Union within the framework of the Erasmus+ Traineeship Programme (2017-1-IT02-KA103-035458). A. Val del Rio is a Xunta de Galicia fellow (ED418B 2017/075). Authors from the USC belong to CRETUS Strategic Partnership (ED431E 2018/01) and to the Galician Competitive Research Group (GRC-ED431C 2017/29). All these programs are co-funded by FEDER (EU) fundsS

The ANAMMOX process as the second step for the treatment of ammonium rich refinery wastewater with high Corg/N ratio

The combination of partial nitritation and anammox (anaerobic ammonium oxidation) has been mainly applied to the treatment of wastewaters with high ammonium concentration and low content of biodegradable organic carbon. So far, only few studies have focused on the application of partial nitritation-anammox process to the treatment of ammonium-rich wastewaters characterized also by a high organic carbon to nitrogen ratio (Corg/N), as well as by the presence of toxic substances: in this study, an anammox reactor was started-up and fed with the effluent from a partial nitritation reactor treating IGCC (Integrated Gasification Combined Cycle) wastewater, in order to evaluate its feasibility as an alternative to the currently applied chemical-physical-biological treatment. A sequencing batch reactor was inoculated with granular anammox biomass and run at controlled temperature (35±0.5 °C) and pH (7.7±0.3). The synthetic influent containing NH4-N (up to 250 mg/L) and NO2-N (up to 330 mg/L) was progressively replaced by the IGCC wastewater, which had been pre-treated in the lab-scale partial nitritation reactor. When the reactor was fed with the synthetic medium at the target nitrogen loading rate (NLR, 0.350 gN/L·d), the observed NH4-N removal efficiency was 93±5%, and no nitrite was detected in the effluent. Good overall process performance was maintained as increasing amounts (up to 65%) of the effluent from the partial nitritation system were fed to the anammox reactor: NH4-N and NO2-N removal efficiencies were 98.9±1.0% and 96.6±2.1%, respectively, and nitrite specific removal rate peaked at 0.28 gNO2-N/gVSS∙d. On day 154, a nitrogen shock load was applied to evaluate anammox stability during start-up: despite system sensitivity to the sudden increase of nitrogen load, process performance was recovered and the percentage of IGCC wastewater in the influent could be raised to 100% with fairly good NH4-N and NO2-N removal efficiencies (85.7±5.8% and 88.2±2.3%, respectively). Anammox granules were compact (diameter, 636±20 m) and dense (86.5±3.4 gTSS/Lgran), with good settling properties. The total organic carbon (TOC) removal efficiency was low: since most of TOC (around 80±8%) had been removed in the preliminary partial nitritation step (results not shown), it can be assumed that the residual TOC entering the anammox reactor was slowly biodegradable, therefore heterotrophic denitrifiers did not compete with anammox biomass for nitrite. The results indicate that anammox start-up can be successfully achieved and the process can be applied in combination with a preliminary partial nitritation step for the treatment of ammonium-rich IGCC wastewater, thus providing useful information also for the treatment of similar wastewaters with high Corg/N ratio and containing toxic substances

Preliminary evaluation of Sharon-Anammox process feasibility to treat Ammonium-rich effluents produced by double-stage anaerobic digestion of food waste

In this study, a Sharon-Anammox system was started up and fed with an ammonium-rich (1,500 mgNH4-N L−1) synthetic medium simulating the effluent produced by double-stage anaerobic digestion of food waste (AD-FW). The effects of different process parameters (e.g., hydraulic retention time, nitrogen loading rate, etc.) and influent characteristics (e.g., influent alkalinity) on reactors performance were thoroughly evaluated. As to the Sharon reactor, reducing the hydraulic retention time did not cause any detrimental effect on overall process performance (the observed NH4-N removal efficiency and effluent NO2-N/NH4-N molar ratio were 60.8 ± 4.5% and 1.58 ± 0.27, respectively), although a slightly longer time was required to achieve process stability. The Anammox reactor was able to withstand the same nitrogen loading rates applied to the Sharon unit, and the observed nitrogen removal rate was high (89.9 ± 0.5%), indicating good process performance. The information gathered in this preliminary study will be useful for the treatment of real AD-FW wastewater