[Nitrification and Bioaugmentation of Biological Treatment System of Sewage Treatment Plant at High Temperature in Summer].

The influence of temperature (30-45℃) and ammonia-nitrogen volume load on the nitrification function and microbial community of activated sludge in an aerobic tank of a sewage treatment plant were investigated under simulated high-temperature stress in the summer. Meanwhile, the bioaugmentation effectiveness of the middle-temperature-enriched nitrifying sludge (with or without acclimation) was evaluated in two biological treatment systems under high-temperature shock. The results showed that the ammonium-nitrogen (NH4+-N) removal efficiency and the nitrifying bacteria content of the aerobic activated sludge at 30-40℃ were above 90% and up to 4.55% and decreased to 40% and 1.97% at 45℃, respectively. To quickly recover the nitrification function of the biological system under high-temperature shock in the summer, the middle-temperature-enriched nitrifying sludge was acclimated at 40℃ for 61 d and achieved (60±5) mg·(L·h)-1 nitrification activity. Then, its bioaugmentation efficiency was compared with that of the middle-temperature-enriched nitrifying sludge. In the bioaugmentation test, 10% of NH4+-N was removed in the reactor inoculated with 5% (volume fraction) of the acclimated nitrifying sludge, while the reactor needed inoculate with 10% (volume fraction) of the middle-temperature-enriched sludge to achieve the same removal efficiency. The results suggested that middle-temperature-enriched nitrifying sludge, after acclimating at 40℃, has a better enhancement effect under a high-temperature shocking load.

Comparative assessment of endocrine disrupting compounds removal in heterotrophic and enriched nitrifying biomass.

Despite the number of studies that have investigated the fate of endocrine disrupting compounds (EDCs), to date results are still contradictory and more research is required to evaluate the contribution of the microbial communities present in different engineered treatment systems. Thus, autotrophic and heterotrophic types of biomass were here compared in terms of efficiency in the removal of estrone (E1), 17ß-estradiol (E2), estriol (E3), 17α-ethynilestradiol (EE2) and bisphenol A (BPA). Experiments were performed with enriched nitrifying activated sludge (NAS) and enriched ammonia oxidizing bacteria (AOB) sludge cultivated at lab-scale, as well as with conventional activated sludge (CAS) from a full-scale wastewater treatment plant. Both enriched NAS and AOB demonstrated a negligible degrading capacity. In both cases, the studied EDCs exhibited low removals (<14%) and showed no correlation with the increasing nitrification rates contradicting some of the hypothesis present in literature. Contrariwise, the biodegradation capabilities of the heterotrophic fraction of CAS were highlighted. E2 and E3 were removed by up to 100% and 78%, respectively. E1 was found to be the main transformation product of E2 (almost quantitative oxidation) and it was also highly eliminated. Finally, EE2 and BPA were more persistent biologically with removals ranging from 10% to 39%. For these two compounds similar removals were obtained during experiments with heat-inactivated biomass suggesting that sorption could be a relevant route of elimination.

[Pilot-scale Experiment on Enrichment of Nitrifying Activated Sludge and Its Application in Enhancing a Wastewater Biological Treatment System Against Ammonia Shocking Loads].

Nitrifying activated sludge (NAS) was enriched in a membrane bioreactor (MBR) with pre-treated municipal wastewater and additional ammonium sulfate as the culture medium. The influences of temperature, dissolved oxygen (DO), ammonia nitrogen volumetric load, free ammonia (FA), and free nitrite (FNA) on the enrichment of NAS were investigated, the cost of the process was evaluated, and then NAS's application in enhancing a wastewater biological treatment system against ammonia shocking loads was attempted. The results showed that after 182 days of cultivation in an MBR, NAS had a nitrification activity of 98.41 mg·(L·h)-1, which was 30-times higher than that of the seeding sludge. The yield of NAS was 14.96 mg·(L·d)-1, costing 3.52 Yuan for 1 kg. Temperature was found to be a key factor affecting the sludge nitrification activity. The sludge nitrification activity was decreased to 1/3 of the maximum value at temperatures below 15.0℃, while lowering the ammonium volumetric load retarded the decrease in the sludge nitrification activity to some extent. In addition, dissolved oxygen deficiency resulted in nitrite accumulation, and thereby slowed down the NAS enrichment rate. The enriched NAS was then applied to a wastewater biological treatment pilot equipment, which had just been exposed to an ammonium shocking load. The removal rate of ammonia nitrogen in the biological system increased from 29.4% to 88.4% after 2.0% of NAS was inoculated. The enhanced biological system retained ammonia removal rates of as high as 99.0%, even as the temperature dropped to 13.3℃±1.6℃ afterwards. The above pilot-experiment results suggested that enriched nitrifying sludge is suitable for quickly increasing the start-up or recovery rates of the nitrifying function in a biological system.

Bacterial diversity and population shifts driven by spotlight wastewater micropollutants in low-temperature highly nitrifying activated sludge.

In this study the influence of low-temperature (8°C), sludge retention time (SRT) and loading of spotlight wastewater micropollutants (MPs) on bacterial community of activated sludge was investigated with a special focus on nitrification. Two Sequencing batch reactors (SBR) and two membrane bioreactors (MBR) were operated with synthetic municipal-like wastewater receiving and not receiving ibuprofen, diclofenac, estrone and 17α-ethynylestradiol (EE2). Bacterial population studies were related to removal efficiencies of studied MPs. The results showed that studied bacterial communities significantly differed from all previously published nitrifying activated sludge communities. Exceptionally low concentration of autotrophic nitrifying bacteria were found (<0.5%) as well as no common heterotrophic nitrifies were presenting in activated sludge and therefore could not be related to the MPs removal. Additionally SRT had a spacious effect on the diversity of bacteria and bacterial population shifts under pressure of MPs. Growth of Firmicutes was suppressed by presence of MPs in all the reactors. Increase of MPs concentrations in wastewater improved the removal of EE2. Abundance of Delta- and Gammaproteobacteria showed positive correlation with diclofenac removal.

Removal of triclosan in nitrifying activated sludge: effects of ammonia amendment and bioaugmentation.

This study investigated two possible strategies, increasing ammonia oxidation activity and bioaugmenting with triclosan-degrader Sphingopyxis strain KCY1, to enhance triclosan removal in nitrifying activated sludge (NAS). Triclosan (2 mg L(-1)) was removed within 96-h in NAS bioreactors amended with 5, 25 and 75 mg L(-1) of ammonium (NH4-N). The fastest triclosan removal was observed in 25 mg NH4-NL(-1) amended-bioreactors where high ammonia oxidation occurred. Inhibition of ammonia oxidation and slower triclosan removal were observed in 75 mg NH4-NL(-1) amended-bioreactors. Triclosan removal was correlated to the molar ratio of the amount of nitrate produced to the amount of ammonium removed. Bioaugmentation with strain KCY1 did not enhance triclosan removal in the bioreactors with active ammonia oxidation. Approximately 36-42% and 59% of triclosan added were removed within 24-h by ammonia-oxidizing bacteria and unknown triclosan-degrading heterotrophs, respectively. The results suggested that increasing ammonia oxidation activity can be an effective strategy to enhance triclosan removal in NAS.