Frédéric Monette’s research while affiliated with École de Technologie Supérieure and other places

Nitrate removal through electroreduction using stainless steel electrodes in recycle mode was found to be enhanced by addition of salts, acids or aluminosilicate-based catalysts such as bentonite, kaolin, illite-montmorillonite mixture and clinoptilolite. High nitrate removal yields were obtained in the presence of salts under optimum flowrate. The ionic strength and current density induced by chlorinated salts appear to promote the electrochemical denitrification. This effect was stronger as compared to that produced by acid addition. Acid addition appears to mainly improve the ionic force. The flowrate effect was found to strongly correlate to those of all added species. These results open promising prospects for low-cost clay-catalyzed nitrate electroreduction under dynamic conditions.

Aluminosilicate-catalyzed electrochemical decomposition of ammonium cation (NH4+NH4+) in water was investigated using NH4+-saturated clinoptilolite and copper-nickel electrodes in the presence of different salts and acidic species. The results showed beneficial roles of chloride anion and moderately acidic media. NH4+ adsorbed by the zeolites was converted with a 98% selectivity into nitrogen. The process was found to obey zero-order kinetics in the presence of clinoptilolite and a first order process when NaCl is added. Beneficial buffering effects of the zeolite and acidic species were registered. Clinoptilolite turned out to act both as catalyst and NH4+ reservoir. These results allow envisaging effective and waste-free technology in treating NH4+-rich aqueous effluents through total electroconversion into nitrogen using low cost aluminosilicates. Clay minerals, soils, sludges and natural water turbidity are potential catalysts for this purpose.

With the strengthening of regulatory requirements regarding ammoniacal nitrogen, several water-treatment plants have to reduce their nitrogen load released. In the aim of promoting nitrification in a Biocarbon® biological filter, aeration, washing parameter modification, and flow reduction tests were conducted. Monitoring was carried out at various depths in the filtering medium. The results show that dissolved oxygen has to be at least 6 mg-O2/L to foster nitrification in the deep part of the filter. Removals in chemical oxygen demand (COD), carbonaceous biochemical oxygen demand over five days (CBOD5), and N–NH4⁺ of 89, 95, and 38% were obtained, respectively, whereas the additional energy consumption was estimated between 69 and 407 kWh/day per kg of CBOD5 and N–NH4⁺ removed. Results suggest that aeration is a key parameter that can be controlled in part by the hydraulic retention time, combined with shorter and more frequent washes stimulating more nitrifying bacteria.

To develop a better understanding for fixed biomass processes, the development of a nitrifying bacterial biofilm, as well as the performance of treatment during modifications to operational conditions of a full-scale submerged biological filter were examined. The development of the nitrifying biofilm was investigated at four depth levels (1, 2, 4 and 5 feet). The result of bacterial subpopulations analyzed by qPCR relative to the physico-chemical parameters of the wastewater during the various tests (sustained aeration, modified backwash parameters and inflow restriction) revealed an increase of the relative presence of nitrifying microorganisms throughout the biofilm (especially for nitrite oxidizing bacteria (NOB)), but this was not necessarily accompanied by a better nitrification rate. The highest observed nitrification rate was 49% of removal in the test cell during backwashing conditions, whereas the relative ammonia oxidizing bacteria (AOB) population was 0.032% and NOB was 0.008% of the total biomass collected. The highest percentage of nitrifying bacteria observed (0.034% AOB and 0.18% NOB) resulted in a nitrification rate of 21%. The treatment of organic matter determined by measuring the chemical and biochemical oxygen demand (COD, CBOD5) was improved.

Changes in extreme precipitation should be one of the primary impacts of climate change (CC) in urban areas. To assess these impacts, rainfall data from climate models are commonly used. The main goal of this paper is to report on the state of knowledge and recent works on the study of CC impacts with a focus on urban areas, in order to produce an integrated review of various approaches to which future studies can then be compared or constructed. Model output statistics (MOS) methods are increasingly used in the literature to study the impacts of CC in urban settings. A review of previous works highlights the non-stationarity nature of future climate data, underscoring the need to revise urban drainage system design criteria. A comparison of these studies is made difficult, however, by the numerous sources of uncertainty arising from a plethora of assumptions, scenarios, and modeling options. All the methods used do, however, predict increased extreme precipitation in the future, suggesting potential risks of combined sewer overflow frequencies, flooding, and back-up in existing sewer systems in urban areas. Future studies must quantify more accurately the different sources of uncertainty by improving downscaling and correction methods. New research is necessary to improve the data validation process, an aspect that is seldom reported in the literature. Finally, the potential application of non-stationarity conditions into generalized extreme value (GEV) distribution should be assessed more closely, which will require close collaboration between engineers, hydrologists, statisticians, and climatologists, thus contributing to the ongoing reflection on this issue of social concern.

Aluminosilicate catalysts (Bentonite, illite-montmorillonite mixture ([I + M]), kaolinite and Clinoptilolite) showed catalytic activity in the electroreduction of nitrates using stainless steel electrodes, in the presence of salts. Addition of NaCl and KCl resulted in process enhancement, affording nitrate removal yields of up to 95% after 30–60 min. They were found to improve of the ionic strength of the aqueous media, without undergoing precipitation with increasing alkalinity in time. Their neutral intrinsic pH seems to preserve the composition of the stainless steel electrodes, and to prevent salt electrolysis into metals as with magnesium. The process selectivity towards nitrogen was examined through a judicious approach involving deeper insights in alkalinity evolution. The lower alkalinity in the presence of catalyst was explained in terms of ammonia consumption via ion-exchange. The major part of alkalinity was found to arise from the continuous formation of ammonia, favored by chemical equilibrium shift for compensating the adsorbed amount of cations until saturation. These results demonstrate unequivocally that low cation exchange capacity and/or previous saturation of the catalyst by cations are essential requirements for hindering the formation of ammonia. This opens new prospects for silica-rich materials for effective nitrate removal without residual ammonia in waters. Free access to this article is valid for 50 days, until February 23, 2017 at: https://authors.elsevier.com/a/1UKLk33-e5tG4

Phytoextraction is one of the main phytoremediation techniques and it has often been described as a potentially feasible in situ soil decontamination method of large amounts of heavy metals, organic pollutants and explosive compounds. As this remediation technique is approaching extensive on-field experimentation and commercialization, research focus is on investigating new ways to achieve the valorisation of its by-products. Biomass pyrolysis represents a key step to numerous valorisation options and it is characterized by differential output products that are determined by the operating conditions of the process and the characteristics of the input. However, when used to valorise plants that have undergone significant metal uptake, this strategy involves some new aspects related to harvest, procedure and final product reutilization. This paper reviews the studies made on biomass pyrolysis of plants with emphasis on the differential quality and distribution of pyrolysis products in relation with the variables of the process and the metal-rich phytoextraction feedstock properties. By investigating these parameters, this survey provides indications on ways to optimize the valorisation of phytoremediation by-products through biomass pyrolysis.

Urban rainfall runoff has been a topic of increasing importance over the past years, a result of both the increase in impervious land area arising from constant urban growth and the effects of climate change on urban drainage. The main goal of the present study is to assess and analyze the correlations between rainfall variables and common indicators of urban water quality, namely event mean concentrations (EMCs) and event fluxes (EFs), in order to identify and explain the impacts of each of the main rainfall variables on the generation process of urban pollutants during wet periods. To perform this analysis, runoff from eight summer rainfall events that resulted in combined sewer overflow (CSO) was sampled simultaneously from two distinct catchment areas in order to quantify discharges at the respective outfalls. Pearson statistical analysis of total suspended solids (TSS), chemical oxygen demand (COD), carbonaceous biochemical oxygen demand at 5 days (CBOD5), total phosphorus (Ptot) and total kedjal nitrogen (N-TKN) showed significant correlations (ρ = 0.05) between dry antecedent time (DAT) and EMCs on one hand, and between total rainfall (TR) and the volume discharged (VD) during EFs, on the other. These results show that individual rainfall variables strongly affect either EMCs or EFs and are good predictors to consider when selecting variables for statistical modeling of urban runoff quality. The results also show that in a combined sewer network, there is a linear relationship between TSS event fluxes and COD, CBOD5, Ptot, and N-TKN event fluxes; this explains 97% of the variability of these pollutants which adsorb onto TSS during wet weather, which therefore act as tracers. Consequently, the technological solution selected for TSS removal will also lead to a reduction of these pollutants. Given the huge volumes involved, urban runoffs contribute substantially to pollutant levels in receiving water bodies, a situation which, in a climate change context, may get much worse as a result of more frequent, shorter, but more intense rainfall events.

Projections from the Canadian Regional Climate Model (CRCM) for the southern part of the province of Québec, Canada, suggest an increase in extreme precipitation events for the 2050 horizon (2041–2070). The main goal of this study consisted in a quantitative and qualitative assessment of the impact of the 20 % increase in rainfall intensity that led, in the summer of 2013, to overflows in the “Rolland-Therrien” combined sewer system in the city of Longueuil, Canada. The PCSWMM 2013 model was used to assess the sensitivity of this overflow under current (2013) and future (2050) climate conditions. The simulated quantitative variables (peak flow, Q CSO, and volume discharged, VD) served as the basis for deriving ecotoxicological risk indices and event fluxes (EFs) transported to the St. Lawrence (SL) River. Results highlighted 15 to 500 % increases in VD and 13 to 148 % increases in Q CSO by 2050 (compared to 2013), based on eight rainfall events measured from May to October. These results show that (i) the relationships between precipitation and combined sewer overflow variables are not linear and (ii) the design criteria for current hydraulic infrastructure must be revised to account for the impact of climate change (CC) arising from changes in precipitation regimes. EFs discharged into the SL River will be 2.24 times larger in the future than they are now (2013) due to large VDs resulting from CC. This will, in turn, lead to excessive inputs of total suspended solids (TSSs) and tracers for numerous urban pollutants (organic matter and nutrients, metals) into the receiving water body. Ecotoxicological risk indices will increase by more than 100 % by 2050 compared to 2013. Given that substantial VDs are at play, and although CC scenarios have many sources of uncertainty, strategies to adapt this drainage network to the effects of CC will have to be developed.

The objective of the study is to compare different development scenarios of a black water source-separation sanitation system (BWS) that could be environmentally and economically more viable than a conventional system (CONV). Scenarios performance is evaluated using life cycle assessment and environmental life cycle costing. System boundaries include the processes related to the collection and treatment of wastewater and organic kitchen refuse collection and the recycling of by-product (digestate/sludge and biogas) produced in the treatment step. The BWS scenario that entails a vacuum toilet flow-volume reduction to 0.5 L/flush results in significantly higher performances than the ones of CONV for the climate change and resources indicators, while involving a significantly lower performance with regards to human health and a comparable cost. The BWS scenario based on digestate mass reduction with reverse osmosis and acidification prior to its transport to farmland achieves comparable performances to the ones of CONV for all indicators. The BWS scenario with digestate treatment by means of phosphorus precipitation (struvite) and nitritation–anammox reactors gives performances that are comparable to the ones of CONV for all indicators, with the exception of climate change, for which this scenario has a significantly lower performance if the electricity is produced by hydropower. When single-pathway scenarios are combined, the multi-pathway scenarios thus created can produce results that are significantly superior to the CONV result for the climate change, resources and human health indicators although the cost remains comparable.