Abstract: The biochemical methane potential test (BMP) is the most common analytical technique to predict the performance of anaerobic digesters. However, this assay is time-consuming (from 20 to over than 100 days) and consequently impractical when it is necessary to obtain a quick result. Several methods are available for faster BMP prediction but, unfortunately, there is still a lack of a clear alternative. Current aerobic tests underestimate the BMP of substrates since they only detect the easily biodegradable COD. In this context, the potential of COD fractionation respirometric assays, which allow the determination of the particulate slowly biodegradable fraction, was evaluated here as an alternative to early predict the BMP of substrates. Seven different origin waste streams were tested and the anaerobically biodegraded organic matter (CODmet) was compared with the different COD fractions. When considering adapted microorganisms, the appropriate operational conditions and the required biodegradation time, the differences between the CODmet, determined through BMP tests, and the biodegradable COD (CODb) obtained by respirometry, were not significant (CODmet (57.8026 +/- 21.2875) and CODb (55.6491 +/- 21.3417), t (5) = 0.189, p = 0.853). Therefore, results suggest that the BMP of a substrate might be early predicted from its CODb in only few hours. This methodology was validated by the performance of an inter-laboratory studyconsidering four additional substrates.

Abstract: Anaerobic digestion (AD) is commonly used for the stabilization of agro-food wastes and recovery of energy as methane. Since AD removes organic C but not nutrients (N and P), additional processes to remove them are usually applied to meet the stringent effluent criteria. However, in the past years, there was a shift from the removal to the recovery of nutrients as a result of increasing concerns regarding limited natural resources and the importance given to the sustainable treatment technologies. Recovering N and P from anaerobically pretreated agro-food wastes as easily transportable and marketable products has gained increasing importance to meet both regulatory requirements and increase revenue. For this reason, this review paper gives a critical comparison of the available and emerging technologies for N and P recovery from AD residues.

Abstract: Nitrification and sulfur-based autotrophic denitrification processes can be used to remove ammonia from wastewater in an economical way. However, under certain operational conditions, these processes accumulate intermediate compounds, such as elemental sulphur, nitrite, and nitrous oxide, that are noxious for the environment. In order to predict the generation of these compounds, an analysis based on the Gibbs free energy of the possible reactions and on the oxidative capacity of the bulk liquid was done on case study systems. Results indicate that the Gibbs free energy is not a useful parameter to predict the generation of intermediate products in nitrification and autotrophic denitrification processes. Nevertheless, we show that the specific productions of nitrous oxide during nitrification, and of elemental sulphur and nitrite during autotrophic denitrification, are well related to the oxidative capacity of the bulk liquid.

Abstract: The operation of wastewater treatment plants results in direct emissions, from the biological processes, of greenhouse gases (GHG) such as carbon dioxide (CO2), methane (CH4), and nitrous oxide (N-2 O), as well as indirect emissions resulting from energy generation. In this study, three possible ways to reduce these emissions are discussed and analyzed: (1) minimization through the change of operational conditions, (2) treatment of the gaseous streams, and (3) prevention by applying new configurations and processes to remove both organic matter and pollutants. In current WWTPs, to modify the operational conditions of existing units reveals itself as possibly the most economical way to decrease N-2 O and CO2 emissions without deterioration of effluent quality. Nowadays the treatment of the gaseous streams containing the GHG seems to be a not suitable option due to the high capital costs of systems involved to capture and clean them. The change of WWTP configuration by using microalgae or partial nitritation-Anammox processes to remove ammonia from wastewater, instead of conventional nitrification-denitrification processes, can significantly reduce the GHG emissions and the energy consumed. However, the area required in the case of microalgae systems and the current lack of information about stability of partial nitritation-Anammox processes operating in the main stream of the WWTP are factors to be considered.

Abstract: The reduced footprint of Aerobic Granular Sludge (AGS) systems constitutes a good alternative to conventional treatments, despite their associated drawbacks (long start-up periods and high aeration requirements for granules formation and integrity). This study presents a pulsed aeration regime as a strategy to overcome these problems. Two AGS sequencing batch reactors (SBRs) were operated treating low-strength wastewater (190 mg COD/L) with pulses of 1 s ON/2 s OFF (R1) and continuous aeration (R2). Initially, different superficial gas velocities (SGV) of 3.6 cm/s (R1) and 1.2 cm/s (R2) were imposed for the same airflow (448 L/cycle). The granulation process was completed in 38 days for R1 whereas it took 48 days for R2. Denser and smaller granules were formed with pulsed regime and phosphate accumulating organisms were developed faster. The removal efficiencies were practically the same in both SBRs, being of 85% for COD, 95% for phosphorus and 30% for nitrogen. After granules formation the airflow in both reactors was reduced. For a SGV of 1.2 cm/s both systems behaved similarly. The minimum SGV required to maintain a uniform mixture of the biomass inside the reactor was 1.2 (R1) and 0.5 cm/s (R2), meaning less air consumption in the pulsed system (149 L/cycle) compared to the continuous one (179 L/min). Therefore, pulsed aeration successfully reduced granulation periods and aeration requirements in AGS systems.

Abstract: Food waste is the main component of municipal solid waste (MSW) and its sustainable management is a global challenge. Co-treatment of food waste and urban wastewater in wastewater treatment plants (WWTPs) could be a plausible management strategy to reduce the MSW amount that is disposed in landfills, while converting its organic fraction into biogas in the WWTP. However, the increased organic load in the wastewater influent would impact the capital and operating costs of the WWTP, mainly due to the increase in sludge production. In this work, different scenarios for co-treatment of food waste and wastewater were studied from both economic and environmental perspectives. These scenarios were designed based on different sludge disposal and management options. The results showed that the co-treatment of food waste and wastewater would be more environmentally friendly than their separate treatment, but its economic feasibility strongly depends on the ratio between the management costs of MSW and sewage sludge.

Abstract: The denitrification process was studied in two granular biomass denitrifying reactors (USB1 and USB2). In USB1 large quantities of biomass were accumulated (9.5 gVSS L-1) allowing for the treatment of high nitrogen loads (3.5 g NO3--N L-1 d(-1)). As the biomass granulation process is not immediate the effects of different upflow velocities (0.12-5.5 m h(-1)) and calcium contents (5-200 mg Ca2+ L-1) were studied in order to speed up the process. Obtained results indicate that the optimum values for these parameters, which allow for the stable operation of USB1, are of 0.19 m h(-1) and 60 mg Ca2+ L-1. Then these optimum conditions were applied to USB2 where the effects of concentrations from 335 to 1000 mg NO3--N L-1 were tested. In these conditions nitrate concentrations of 1000 mg NO3--N L-1 are required for denitrifying granular biomass formation. Summarizing denitrifying granules can be formed at low upflow velocities and in hard or extremely hard water composition conditions if sufficient high nitrogen loads are treated. (C) 2015 Elsevier Ltd. All rights reserved.

Abstract: The inhibitory effect of seven different metals on the specific anammox activity of granular biomass, collected from a single stage partial nitritation/anammox reactor, was evaluated. The concentration of each metal that led to a 50% inhibition concentration (IC50) was 19.3 mg Cu+2/L, 26.9 mg Cr+2/L, 45.6 mg Pb+2/L, 59.1 mg Zn+2/L, 69.2 mg Ni+2/L, 174.6 mg Cd+2/L, and 175.8 mg Mn+2/L. In experiments performed with granules mechanically disintegrated (flocculent-like sludge), the IC50 for Cd+2 corresponded to a concentration of 93.1 mg Cd+2/L. These results indicate that the granular structure might act as a physical barrier to protect anammox bacteria from toxics. Furthermore, the presence of an external layer of ammonia oxidizing bacteria seems to mitigate the inhibitory effect of the metals, as the values of IC50 obtained in this study for anammox activity were higher than those previously reported for anammox granules. Additionally, the results obtained confirmed that copper is one of the most inhibitory metals for anammox activity and revealed that chromium, scarcely studied yet, has a similar potential inhibitory effect.

Abstract: The effects of orange azo dye over ammonia oxidizing bacteria (AOB) and anammox bacteria activities were tested. Performed batch tests indicated that concentrations lower than 650 mg(orange)/L stimulated AOB activity, while anammox bacteria activity was inhibited at concentrations higher than 25 mg(orange)/L. Long-term performance of a continuous stirred tank reactor (CSTR) for the partial nitritation and a sequencing batch reactor (SBR) for the anammox process was tested in the presence of 50 mg(orange)/L. In the case of the partial nitritation process, both the biomass concentration and the specific AOB activity increased after 50 days of orange azo dye addition. Regarding the anammox process, specific activity decreased down to 58% after 12 days of operation with continuous feeding of 50 mg(orange)/L. However, the anammox activity was completely recovered only 54 days after stopping the dye addition in the feeding. Once the biomass was saturated the azo dye adsorption onto the biomass was insignificant in the CSTR for the partial nitritation process fed with 50 mg(orange)/L. However, in the SBR the absorption was determined as 6.4 mg(orange)/g volatile suspended solids. No biological decolorization was observed in both processes.

Abstract: Aerobic granular sludge represents an interesting approach for simultaneous organic matter and nitrogen removal in wastewater treatment plants. However, the information about microbial communities in aerobic granular systems dealing with industrial wastewater like pig slurry is limited. Herein, bacterial diversity and dynamics were assessed in a pilot scale plant using aerobic granular sludge for organic matter and nitrogen elimination from swine slurry during more than 300 days. Results indicated that bacterial composition evolved throughout the operational period from flocculent activated sludge, used as inoculum, to mature aerobic granules. Bacterial diversity increased at the beginning of the granulation process and then declined due to the application of transient organic matter and nitrogen loads. The operational conditions of the pilot plant and the degree of granulation determined the microbial community of the aerobic granules. Brachymonas, Zoogloea and Thauera were attributed with structural function as they are able to produce extracellular polymeric substances to maintain the granular structure. Nitrogen removal was justified by partial nitrification (Nitrosomonas) and denitrification (Thauera and Zoogloea), while Comamonas was identified as the main organic matter oxidizing bacteria. Overall, clear links between bacterial dynamics and composition with process performance were found and will help to predict their biological functions in wastewater ecosystems improving the future control of the process. (c) 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:1212-1221, 2016