On anammox activity at low temperature: effect of ladderane composition and process conditions.

The application of partial nitritation-anammox (PN/A) under mainstream conditions can enable substantial cost savings at wastewater treatment plants (WWTPs), but how process conditions and cell physiology affect anammox performance at psychrophilic temperatures below 15 °C remains poorly understood. We tested 14 anammox communities, including 8 from globally-installed PN/A processes, for (i) specific activity at 10-30 °C, (ii) composition of membrane lipids, and (iii) microbial community structure. We observed that membrane composition and cultivation temperature were closely related to the activity of anammox biomasses. The size of ladderane lipids and the content of bacteriohopanoids were key physiological components related to anammox performance at low temperatures. We also indicate that the adaptation of mesophilic cultures to psychrophilic regime necessitates months, but in some cases can take up to 5 years. Interestingly, biomass enriched in the marine genus "Candidatus Scalindua" displayed outstanding potential for nitrogen removal from cold streams. Collectively, our comprehensive study provides essential knowledge of cold adaptation mechanism, will enable more accurate modelling and suggests highly promising target anammox genera for inoculation and set-up of anammox reactors, in particular for mainstream WWTPs.

Effects of barium on the pathways of anaerobic digestion.

The sufficient presence of trace elements (TE) is essential for anaerobic digestion. Barium (Ba) is considered a non-essential trace element that can be collaterally added to digesters as part of low-cost trace element sources or because of its presence in some feedstocks, such as crude glycerol. In the present study, the impact of Ba supplementation (2-2000 mg/L) on each stage of the anaerobic digestion (AD) process was evaluated using pure substrates (i.e., cellulose, glucose, a mixture of volatile fatty acids, sodium acetate and hydrogen) as well as a complex substrate (i.e., dried green fodder). Hydrolytic activity was affected at dosages higher than 200 mg Ba/L, whereas cellulose degradation was completely inhibited at 2000 mg Ba/L. The negative effects of the addition of Ba to methane production were observed only in the hydrolytic activity, and no effects were detected at any barium dosage in the subsequent anaerobic steps. Because Ba does not have a reported role as a cofactor of enzymes, this response could have been due to a direct inhibitory effect, a variation in the bioavailability of other trace elements, or even the availability of CO2/SO4 through precipitation as Ba-carbonates and sulphates. The results showed that the addition of Ba modified the chemical equilibrium of the studied system by varying the soluble concentration of some TEs and therefore their bioavailability. The highest variation was detected in the soluble concentration of zinc, which increased as the amount of Ba increased. Although little research has shown that Ba has some utility in anaerobic processes, its addition must be carefully monitored to avoid an undesirable modification of the chemical equilibrium in the system.

Simple biogas desulfurization by microaeration - Full scale experience.

Hydrogen sulfide in biogas is common problem during anaerobic treatment of wastewater with high sulfate concentration (breweries, distilleries, etc.) and needs to be removed before biogas utilization. Physico-chemical desulfurization methods are energetically demanding and expensive compare to biochemical methods. Microaeration, i.e. dosing of small amount of air, is suitable and cost effective biochemical method of sulfide oxidation to elemental sulfur. It has been widely used in biogas plants, but its application in anaerobic reactors for wastewater treatment has been rarely studied or tested. The lack of full-scale experience with microaeration in wastewater treatment plants has been overcome by evaluating the results of seven microaerobic digesters in central Europe. The desulfurization efficiency has been more than 90% in most of the cases. Moreover, microaeration improved the degradability of COD and volatile suspended solids.

Good servant, bad master: sulfide influence on partial nitritation of sewage.

When applying partial nitritation (PN) to anaerobically pre-treated sewage, ammonium oxidizing bacteria (AOB) and nitrite oxidizing bacteria (NOB) will be exposed to dissolved sulfide and methane. Both sulfide and methane may inhibit nitrification. To gain knowledge necessary for sustaining PN under these conditions, we exposed an AOB enrichment and a mixed nitrifying culture to dissolved sulfide and methane. In the mixed nitrifying culture, sulfide selectively inhibited NOB activity (KI,AOB1 = 150 mg-S L-1, KI,NOB = 10 mg-S L-1) which shows that sulfide may help establish PN. The AOB enrichment showed similar KI,AOB2 (130 mg-S L-1), but nitritation activity lagged longer than the time necessary to remove sulfide from the liquid. This demonstrates that feeding of sulfide into established PN should be avoided. Methane inhibition of AOB enrichment was assessed in batch assays with 10 mg-CH4 L-1. As compared to control without methane, AOB enrichment activity was identical. Up to 51% of methane was converted to methanol, thus reducing the greenhouse gas emissions.

Applicability of one-stage partial nitritation and anammox in MBBR for anaerobically pre-treated municipal wastewater.

Energy consumption of municipal wastewater treatment plants can be reduced by the anaerobic pre-treatment of the main wastewater stream. After this pre-treatment, nitrogen can potentially be removed by partial nitritation and anammox (PN/A). Currently, the application of PN/A is limited to nitrogen-rich streams (>500 mg L(-1)) and temperatures 25-35 °C. But, anaerobically pretreated municipal wastewater is characterized by much lower nitrogen concentrations (20-100 mg L(-1)) and lower temperatures (10-25 °C). We operated PN/A under similar conditions: total ammonium nitrogen concentration 50 mg L(-1) and lab temperature (22 °C). PN/A was operated for 342 days in a 4 L moving bed biofilm reactor (MBBR). At 0.4 mg O2 L(-1), nitrogen removal rate 33 g N m(-3) day(-1) and 80 % total nitrogen removal efficiency was achieved. The capacity of the reactor was limited by low AOB activity. We observed significant anammox activity (40 g N m(-3) day(-1)) even at 12 °C, improving the applicability of PN/A for municipal wastewater treatment.

Monitoring COVID-19 spread in selected Prague's schools based on the presence of SARS-CoV-2 RNA in wastewater.

The COVID-19 pandemic has demanded a broad range of techniques to better monitor its extent. Owing to its consistency, non-invasiveness, and cost effectiveness, wastewater-based epidemiology has emerged as a relevant approach to monitor the pandemic's course. In this work, we analyzed the extent of the COVID-19 pandemic in five primary schools in Prague, the Czech Republic, and how different preventive measures impact the presence of SARS-CoV-2 RNA copy numbers in wastewaters. Copy numbers were measured by reverse transcription-multiplex quantitative real-time PCR. These copy numbers were compared to the number of infected individuals in each school identified through regular clinical tests. Each school had a different monitoring regime and subsequent application of preventive measures to thwart the spread of COVID-19. The schools that constantly identified and swiftly quarantined infected individuals exhibited persistently low amounts of SARS-CoV-2 RNA copies in their wastewaters. In one school, a consistent monitoring of infected individuals, coupled with a delayed action to quarantine, allowed for the estimation of a linear model to predict the number of infected individuals based on the presence of SARS-CoV-2 RNA in the wastewater. The results show the importance of case detection and quarantining to stop the spread of the pandemic and its impact on the presence of SARS-CoV-2 RNA in wastewaters. This work also shows that wastewater-based epidemiological models can be reliably used even in small water catchments, but difficulties arise to fit models due to the nonconstant input of viral particles into the wastewater systems.

Potentials and limits of anaerobic digestion of sewage sludge: energy self-sufficient municipal wastewater treatment plant?

Anaerobic digestion is the only energy-positive technology widely used in wastewater treatment. Full-scale data prove that the anaerobic digestion of sewage sludge can produce biogas that covers a substantial amount of the energy consumption of a wastewater treatment plant (WWTP). In this paper, we discuss possibilities for improving the digestion efficiency and biogas production from sewage sludge. Typical specific energy consumptions of municipal WWTPs per population equivalent are compared with the potential specific production of biogas to find the required/optimal digestion efficiency. Examples of technological measures to achieve such efficiency are presented. Our findings show that even a municipal WWTP with secondary biological treatment located in a moderate climate can come close to energy self-sufficiency. However, they also show that such self-sufficiency is dependent on: (i) the strict optimization of the total energy consumption of the plant, and (ii) an increase in the specific biogas production from sewage sludge to values around 600 L per kg of supplied volatile solids.

How biomass growth mode affects ammonium oxidation start-up and NOB inhibition in the partial nitritation of cold and diluted reject water.

The inhibition of undesirable nitrite oxidizing bacteria (NOB) and desirable ammonium oxidizing bacteria (AOB) by free ammonia (FA) and free nitrous acid (FNA) in partial nitritation (PN) is crucially affected by the biomass growth mode (suspended sludge, biofilm, encapsulation). But, the limitations of these modes towards less concentrated reject waters (≤600 mg-N L-1) are unclear. Therefore, this work compares the start-up and stability of three PN sequencing batch reactors (SBRs) with biomass grown in one of the three modes: suspended sludge, biofilm and biomass encapsulated in polyvinyl alcohol (PVA) pellets. The SBRs were operated at 15°C with influent total ammonium nitrogen (TAN) concentrations of 75-600 mg-TAN L-1. PN start-up was twice as fast in the biofilm and encapsulated biomass SBRs than in the suspended sludge SBR. After start-up, PN in the biofilm and suspended sludge SBRs was stable at 150-600 mg-TAN L-1. But, at 75 mg-TAN L-1, full nitrification gradually developed. In the encapsulated biomass SBR, full nitrification occurred even at 600 mg-TAN L-1, showing that NOB in this set-up can adapt even to 4.3 mg-FA L-1 and 0.27 mg-FNA L-1. Thus, PN in the biofilm was best for the treatment of an influent containing 150-600 mg-TAN L-1.

Cold shocks of Anammox biofilm stimulate nitrogen removal at low temperatures.

The adaptation of Anammox (ANaerobic AMMonium OXidation) to low temperatures (10-15°C) is crucial for sustaining energy-efficient nitrogen removal from the mainstream of municipal wastewater. But, current adaptation methods take months or even years. To speed up the adaption of Anammox to low temperatures, this study describes a new approach: exposing Anammox microorganisms to an abrupt temporary reduction of temperature, i.e., cold shock. Anammox biomass in a moving bed biofilm reactor was subjected to three consecutive cold shocks (reduction from 24 ± 2 to 5.0 ± 0.2°C), each taking eight hours. Before the cold shocks, Anammox activity determined in ex situ tests using the temperature range of 12.5-19.5°C was 0.005-0.015 kg-N kg-VSS-1 day-1 . Cold shocks increased the activity of Anammox at 10°C to 0.054 kg-N kg-VSS-1 day-1 after the third shock, which is similar to the highest activities obtained for cold-enriched or adapted Anammox reported in the literature (0.080 kg-N kg-VSS-1 day-1 ). Fluorescence in situ hybridization analysis showed that Ca. Brocadia fulgida was the dominant species. Thus, cold shocks are an intriguing new strategy for the adaptation of Anammox to low temperature. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 34:277-281, 2018.