Identifying economical route for crude glycerol valorization: Biodiesel versus polyhydroxy-butyrate (PHB)

Crude glycerol, a by-product of biodiesel industry, has been used for production of biodiesel and polyhydroxy-alkanoates. But question is: which product is economically favorable using crude glycerol as substrate? In this study, energy balance and economic assessment has been carried out for crude glycerol valorization for B10 biodiesel and polyhydroxy-butyrate (PHB) production. For same quantity of crude glycerol utilized, energy ratio for B10 production was higher than PHB production while unit production cost for B10 was lower than that of PHB. For 50 million L plant capacity of biodiesel, unit production cost was 0.77 $/L B10 while for 2 million kg plant capacity of PHB, unit production cost was 4.88 $/kg PHB. Thus, in present scenario production of biodiesel seems economically better than production of PHA with crude glycerol as raw material. This study is useful for researchers, environmental scientists and industries in identifying effective route for crude glycerol valorization.

Food waste valorization: Energy production using novel integrated systems

Management of food waste (FW) is a global challenge due to increasing population and economic activities. Presently, landfill and incineration are the keyways of FW management, while economical and environmental sustainability have been an issue. Therefore, the biological processes have been investigated for resource and energy recovery from FW. However, these biological approaches have certain drawbacks and cannot be a complete solution for FW management. Therefore, this review aims to offer a detailed and complete analysis of current available technologies to achieve environmental and economical sustainability. In this context, zero solid waste discharge for resource and energy recovery has been put into view. Corresponding to which several innovative technologies using integrated biological methods for resource and energy recovery from FW have been elucidated.

Treatment of microplastics in water by anodic oxidation: A case study for polystyrene

Water pollution by microplastics (MPs) is a contemporary issue which has recently gained lots of attentions. Despite this, very limited studies were conducted on the degradation of MPs. In this paper, we reported the treatment of synthetic mono-dispersed suspension of MPs by using electrooxidation (EO) process. MPs synthetic solution was prepared with distilled water and a commercial polystyrene solution containing a surfactant. In addition to anode material, different operating parameters were investigated such as current intensity, anode surface, electrolyte type, electrolyte concentration, and reaction time. The obtained results revealed that the EO process can degrade 58 ± 21% of MPs in 1 h. Analysis of the operating parameters showed that the current intensity, anode material, electrolyte type, and electrolyte concentration substantially affected the MPs removal efficiency, whereas anode surface area had a negligible effect. In addition, dynamic light scattering analysis was performed to evaluate the size distribution of MPs during the degradation. The combination of dynamic light scattering, scanning electron microscopy, total organic carbon, and Fourier-transform infrared spectroscopy results suggested that the MPs did not break into smaller particles and they degrade directly into gaseous products. This work demonstrated that EO is a promising process for degradation of MPs in water without production of any wastes or by-products.

Acclimatization of microbial community of submerged membrane bioreactor treating hospital wastewater

This study was performed to understand the dynamics of the microbial community of submerged membrane bioreactor during the acclimatization process to treat the hospital wastewater. In this regard, three acclimatization phases were examined using a mixture of synthetic wastewater (SWW) and real hospital wastewater (HWW) in the following proportions; In Phase 1: 75:25 v/v (SWW: HWW); Phase 2: 50:50 v/v (SWW: HWW); and Phase 3: 25:75 v/v (SWW: HWW) of wastewater. The microbial community was analyzed using Illumina high throughput sequencing to identify the bacterial and micro-eukaryotes community in SMBR. The acclimatization study clearly demonstrated that shift in microbial community composition with time. The dominance of pathogenic and degrading bacterial communities such as Mycobacterium, Pseudomonas, and Zoogloea was observed at the phase 3 of acclimatization. This study witnessed the major shift in the micro-eukaryotes community, and the proliferation of fungi Basidiomycota was observed in phase 3 of acclimatization.

A review on recovery of proteins from industrial wastewaters with special emphasis on PHA production process: Sustainable circular bioeconomy process development

The economy of the polyhydroxyalkanoate (PHA) production process could be supported by utilising the different by-products released simultaneously during its production. Among these, proteins are present in high concentrations in liquid stream which are released after the cell disruption along with PHA granules. These microbial proteins can be used as animal feed, adhesive material and in manufacturing of bioplastics. The recycling of the protein containing liquid stream also serves as a promising approach to maintain circular bioeconomy in the route. For this aim, it is important to obtain good yield and limit the drawbacks of protein recovery processes and associated costs. The review focuses on recycling of the liquid stream generated during acid/thermal-alkali treatment for PHA production that would close the gap in linear economy and attain circularity in the process. Examples to recover proteins from other industrial waste streams along with their applications have also been discussed.

Electro-oxidation of secondary effluents from various wastewater plants for the removal of acetaminophen and dissolved organic matter

Electro-oxidation of acetaminophen (ACT) in three different doped secondary effluents collected from a conventional Municipal Waste Water Treatment Plant (MWWTP), a MWWTP using a membrane bioreactor (WWTP MBR) and a lab-scale MBR treating source-separated urine (Urine MBR) was investigated by electro-Fenton (EF) coupled with anodic oxidation (AO) using sub-stoichiometric titanium oxide anode (Ti₄O₇). After 8 h of treatment, 90 ± 15%, 76 ± 3.8% and 46 ± 1.3% of total organic carbon removal was obtained for MWWTP, MWWTP-MBR and Urine-MBR respectively, at a current intensity of 250 mA, pH of 3 and [Fe²⁺] = 0.2 mM. Faster degradation of ACT was observed in the WWTP MBR because of the lower amount of competitive organic matter, however, >99% degradation of ACT was obtained after 20 min for all effluents. The acute toxicity of the treated effluent was measured using Microtox® tests. Results showed an initial increase in toxicity, which could be assigned to formation of more toxic by-products than parent compounds. From 3D excitation and emission matrix fluorescence (3DEEM), different reactivity was observed according to the nature of the organic matter. Particularly, an increase of low molecular weight organic compounds fluorescence was observed during Urine MBR treatment. This could be linked to the slow decrease of the acute toxicity during Urine MBR treatment and ascribed to the formation and recalcitrance of toxic organic nitrogen and chlorinated organic by-products. By comparison, the acute toxicity of other effluents decreased much more rapidly. Finally, energy consumption was calculated according to the objective to achieve (degradation, absence of toxicity, mineralization).

Effect of cathode material and charge loading on the nitrification performance and bacterial community in leachate treating Electro-MBRs

Electro-MBR technology, which combines an electrocoagulation process inside the mixed liquor of a membrane bioreactor, was studied for the treatment of a high-strength ammonia leachate (124 ± 4 mg NH₄-N L^-1). A lab-scale aerobic Electro-MBR was operated with a solid retention time of 45 days, hydraulic retention times of 24h and 12h, and charge loading ranging from 100 to 400 mAh L^-1. At 400 mAh L^-1, with a combination of a Ti/Pt cathode and a sacrificial iron anode, removal percentages for ammonia nitrogen, total organic carbon, and total phosphorus were 99.8%, 38%, and 99.0%, respectively. At 400 mAh L^-1, the estimated ferric ion dosage was 325 mg Fe³⁺ L^-1. Experiments conducted with different cathode materials showed that previously reported inhibition phenomena may result from a cathodic nitrate reduction into ammonia nitrogen. Conventional cathode materials, such as graphite, have electrochemical nitrate reduction rates of -0.03 mg NO₃-N mAh^-1. By comparison, when using Ti/Pt, the rate was -0.0045 mg NO₃-N mAh^-1(85% lower than graphite due to its low hydrogen overpotential). Charge loading tested in this study had no significant impact on both nitrification performance and microbial population diversity. However, the relative abundance of the mixed liquor's Nitrosomonas increased from 4.8% to 8.2% when the charge loading increased from 0 to 400 mAh L^-1. Results from this study are promising for future applications of the Ti/Pt - Iron Electro-MBR in various high-strength ammonia wastewater treatment applications.

Photocatalytic Degradation of Myclobutanil and Its Commercial Formulation with TiO₂ P25 in Slurry and TiO₂/β-SiC Foams

Viticulture is one of the crops most subject to pest control by fungicides. Their drainage towards the fresh water affects the aquatic environment, the fauna, the flora and especially the human health. It is therefore necessary to find an adequate solution to solve this problem. Heterogeneous photocatalysis is an advanced oxidation method for the degradation and mineralization of organic pollutants in water and air using semi-conductor (e.g., TiO²). TiO₂ P25 in suspension (0.75 g·L^-1) is used to treat Myclobutanil contaminated water and a commercial formulation Systhane™ 20EW, a fungicide produced by BASF. After 120 min of batch treatment under our conditions (pH = 6.7, Co = 10 mg ·L^-1), 96% and 98% of Myclobutanil and Systhane were removed with 94% and 92% mineralization, respectively. In order to avoid the recovery of nanoparticles of TiO² P25 after treatment, we have taken care of β-SiC foam cells. Under the same experimental conditions, 45% and 56% of Myclobutanil and Systhane degraded after 4 h with mineralization of 29% and 27%, respectively in recirculation in a fixed-light photoreactor by UV-A lamps. These results are very encouraging: filtering is not necessary to separate the catalyst from the treated water, it is very important for large-scale use of this process.

Ciprofloxacin removal via sequential electro-oxidation and enzymatic oxidation

The combination of electro-oxidation and enzymatic oxidation was tested to evaluate the potency of this system to remove ciprofloxacin (CIP), a fluoroquinolone antibiotic, from water. For the electro-oxidation boron-doped diamond (BDD) and mixed metal oxides anodes were tested, at three current densities (4.42, 17.7 and 35.4 A/cm²). BDD anode at 35.4 A/cm² exhibited the highest removal efficiency in the shortest time (>90 % removal in 6 min). For the enzymatic oxidation, laccase from Trametes versicolor was chosen. Laccase alone was not able to remove CIP; hence the influence of redox mediators was investigated. The addition of syringaldehyde (SA) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) resulted in enhanced CIP transformation. About 48.9±4.0 % of CIP remained after 4 h of treatment when SA-mediated laccase was applied and 87.8±6.6 % in the case of ABTS-mediated laccase. The coupling of enzymatic oxidation followed by electro-oxidation led to 73 % removal of the antibiotic. Additionally, the antimicrobial activity increased up to its original efficiency after the treatment. The combination of electro-oxidation followed by enzymatic oxidation led to 97-99 % removal of CIP. There was no antimicrobial activity of the solution after the treatment. The tests with wastewater confirmed the efficacy of the system to remove CIP from the complex matrix.

Techno-economic analysis for extracellular-polymeric substances (EPS) production using activated sludge fortified with crude glycerol as substrate and its application in leachate treatment

Economic assessment of bio-flocculant production process has been carried out by SuperPro Designer where extracellular-polymeric substances (EPS) were produced using activated sludge fortified with crude glycerol in fermenter followed by centrifugation. Considering EPS concentration of 60 g/L in production fermenter at 96 h, the unit production cost for slime EPS was estimated to be $ 0.95/L. The unit price of S-EPS was sensitive to inoculum size and EPS productivity (EPS concentration and fermentation time) in the fermented broth. Economic analysis was also conducted for EPS aided leachate treatment. The unit leachate treatment cost was 7.78 $/m³ and was sensitive to S-EPS unit production cost. To get same leachate treatment cost as current industrial practice (4 $/m³), S-EPS unit production cost should lower down to $ 0.5/L. The process has several advantages: 1) sludge and crude glycerol valorization for bio-flocculant production 2) Leachate treatment using environment friendly bio-flocculant.

Electro-generation of hydrogen peroxide using a graphite cathode from exhausted batteries: study of influential parameters on electro-Fenton process

In this work, the study of hydrogen peroxide (H₂O₂) electro-generation using graphite from exhausted batteries (Gr-Bat) was conducted. Linear sweep voltammetry and electrolysis experiments were carried out in a single compartment electrochemical cell. Study of the possibility to use this electrode revealed that it presents, as vitreous carbon (VC) electrode, a reduction of oxygen with two successive waves (bi-electronic reduction). The first wave corresponds to the reduction of O₂ to H₂O₂, while the second one corresponds to the reduction of H₂O₂ to H₂O. The cathodic potentials for electro-generation of H₂O₂ appeared at -600 and -700 mV vs. Ag/AgCl for Gr-Bat and VC electrodes, respectively. Subsequently, electrolysis experiments were conducted by imposing the potentials required for H₂O₂ formation. The effect of several operating parameters on H₂O₂ production, such as the nature and concentration of the electrolyte, the pH, the presence of ferrous ions and O₂ injection were studied using Gr-Bat and VC electrodes, respectively. For both electrodes, the acidic medium was more favorable for H₂O₂ electro-generation. The oxygen injection in solution promoted an increase of H₂O₂ concentration, but its effect was more pronounced in the case of VC electrode. Application for crystal violet degradation by electro-Fenton revealed that Gr-Bat had the best purification performance. A removal rate of 73.18% was obtained with Gr-Bat electrode against 62.27% with VC electrode for an electrolysis time of 120 min. This study has demonstrated the possibility of recycling Gr-Bat by using them as cathode materials in the electro-Fenton process.

MBR treatment of leachates originating from waste management facilities: A reference study of the design parameters for efficient treatment

The main objective of the study was to define the interaction between the solid retention time (SRT) and the contaminant loading rate on a membrane bioreactor's efficacy in removing contaminants frequently detected (chemical oxygen demand (COD), NH₄⁺, total phosphorus and metals) above the discharge criteria in waste-originating leachates. The rates and coefficient calculated from this study's experimental data can be used for the design of membrane bioreactor treating wastewaters, even beyond the scope of this experiment. Over a period of 152 days, SRTs of 28 and 47 days and HRTs of 13, 25, 36 and 52 h were studied using a real leachate with a constant composition. Results showed that membrane bioreactors can efficiently treat >1850 mg COD L^-1 d^-1 of highly to moderately biodegradable COD, with the SRT having no significant impact on the removal of recalcitrant COD. Overall ammonium removal rates of >740 mg NH₄-N L^-1 d^-1 can be achieved as long as a residual alkalinity of 200 mg CaCO₃ L-1 and an adequate dissolved oxygen concentration (6-7 mg L^-1) are both maintained. Overall phosphorus removal rates are independent of the phosphorus loading rate. However, the highest overall phosphorus removal rate (39 ± 2 mg P per g of total suspended solids) was obtained at the lowest SRT (28 days) due to an increased extracellular polymeric substance production. Finally, membrane bioreactor's metal removal capacity is mostly dependent on the metals' affinity to both the leachate's recalcitrant COD as well as sludge concentrations.

Identifying the link between MBRs' key operating parameters and bacterial community: A step towards optimized leachate treatment

A MBR treating compost leachate was studied in order to link the operating parameters (solid and hydraulic retention time) to contaminant's specific bacterial catabolic activity. In this context, a lab-scale aerobic membrane bioreactor was operated for 200 days, at solid retention times (SRT) of 30 and 45 days and four different contaminant load rates. Results showed that increasing the food to microorganism ratio (F/M) by increasing the contaminant load rates lessened the selectivity pressure, which allowed the proliferation of subdominant operational taxonomic units (OTU) (relative abundance >3%) that were otherwise inhibited by highly adapted dominant OTUs (relative abundance >10%). Subsequently, increasing the SRT resulted in a lower species richness and the selection of two dominant types of bacteria: 1) genera with low growth rates that feed on non-limiting substrates or substrates with few competitors, and 2) genera with metabolisms that are highly specific to the available substrates and that can outcompete the other genera by using the substrate more efficiently. The bacterial population evolution observed during this study suggests that the mixed liquor population diversity and structure can be modulated with the operating conditions for the bioenhancement of contaminant specific catabolic activity. Identified dominant and subdominant genera were linked to the MBR's NH₄⁺ and COD removal performances. Interestingly, nitrification performances were unaffected by the organic load rate and the Nitrosomonas relative abundance.

Cost, energy and GHG emission assessment for microbial biodiesel production through valorization of municipal sludge and crude glycerol

In this study, cost simulations were made based on 20 million L blended biodiesel B-10 production per year using INRS and conventional process. In case of INRS process, microbial lipid was produced by T. oleaginosus using washed municipal secondary sludge fortified with crude glycerol while lipid was extracted from wet biomass using biodegradable surfactant and petroleum-diesel (PD). The conventional process uses commercial substrates for lipid production and organic solvents for lipid extraction from dry biomass. The unit B-10 production cost of INRS process was estimated to be $ 0.72/L for an annual capacity of 20 million L, which is 9.5 times more economical than conventional biodiesel production process. For INRS process, the unit B-10 biodiesel production cost was sensitive to plant capacity and lipid productivity during the fermentation. INRS process exhibited positive net energy gain and positive GHG capture, which proves to be energetically and environmentally viable.

The bacterial community structure of submerged membrane bioreactor treating synthetic hospital wastewater

The pharmaceuticals are biologically active compounds used to prevent and treat diseases. These pharmaceutical compounds were not fully metabolized by the human body and thus excreted out in the wastewater stream. Thus, the study on the treatment of synthetic hospital wastewater containing pharmaceuticals (ibuprofen, carbamazepine, estradiol and venlafaxine) was conducted to understand the variation of the bacterial community in a submerged membrane bioreactor (SMBR) at varying hydraulic retention time (HRT) of 6, 12 and 18 h. The variation in bacterial community dynamics of SMBR was studied using high throughput sequencing. The removal of pharmaceuticals was uniform at varying HRT. The removal of both ibuprofen and estradiol was accounted for 90%, whereas a lower removal of venlafaxine (<10%) and carbamazepine (>5%) in SMBR was observed. The addition of pharmaceuticals alters the bacterial community structure and result in increased abundance of bacteria (e.g., Flavobacterium, Pedobacter, and Methylibium) reported to degrade toxic pollutant.

Kinetics and mechanism of Paraquat's degradation: UV-C photolysis vs UV-C photocatalysis with TiO2/SiC foams

In this study, the photolytic and photocatalytic removal of the herbicide paraquat is investigated under UV-C (254 nm). For photocatalytic experiments, SiC foams were used with P25-TiO₂ nanoparticles deposited by dip-coating. The foams were characterized by scanning electron microscopy and paraquat's degradation under UV-C photolysis or photocatalysis, followed by UV-vis spectroscopy, total organic carbon analyzer, LC-MS and ion chromatography. After 3 h of reactions by photolysis and photocatalysis, 4% and 91% of TOC removal were observed. An analysis of degradation by-products showed a similar degradation pathway with pyridinium ions observed by LC/MS and carboxylic acids (succinate, acetate, oxalate and formate) detected by ion chromatography. In conclusion, these two different photo-degradation processes are able to remove paraquat and produce similar by-products. However, the kinetics of degradation is rather slow during photolysis and it is recommended to combine the UV-C lightning with a TiO₂ photocatalyst to improve the mineralization rate.

Appearance of ciprofloxacin/chlortetracycline-resistant bacteria in waters of Québec City in Canada

Most of the waterborne fecal pathogens belong to the family of Gram-negative bacteria. Hence, minimal inhibitory concentrations of chlortetracycline and ciprofloxacin antibiotics towards Gram-negative representative, Enterobacter aerogenes were estimated, which were 7 μg/ml and 0.125 μg/ml, respectively. The combined antimicrobial effect of chlortetracycline and ciprofloxacin against E. aerogenes was also investigated to establish their potential interaction towards the pathogens present in water. Eventually, the water samples obtained from various drinking water treatment plants from Québec municipality were tested for the occurrence of chlortetracycline-, ciprofloxacin- and chlortetracycline/ciprofloxacin-resistant strains.

Microwave-assisted one-pot conversion of agro-industrial wastes into levulinic acid: An alternate approach

Brewery liquid waste (BLW), brewery spent grain (BSG), apple pomace solid wastes (APS), apple pomace ultrafiltration sludge (APUS) and starch industry waste (SIW) were evaluated as alternative feedstocks for levulinic acid (LA) production via microwave-assisted acid-catalyzed thermal hydrolysis. LA production of 204, 160, 66, 49 and 12 g/kg was observed for BLW, BSG, APS, APUS, and SIW, respectively, at 140 °C, 40 g/L substrate concentration (SC), 60 min and 2 N HCl (acid concentration). Based on the screening studies, BLW and BSG were selected for optimization studies using response surface methodology. Maximum LA production of 409 and 341 g/kg for BLW and BSG, respectively were obtained at 160 °C, 4.5 M HCl, 85 g/L SC and 27.5 min. Results demonstrated the possibility of using brewery wastes as promising substrates for economical and higher yield production of LA, a renewable platform chemical and versatile precursor for fuels and chemicals.

Optimization process of organic matter removal from wastewater by using Eichhornia crassipes

This study aimed to determine the optimal conditions for organic matter removal from wastewater by Eichhornia crassipes (E.C). As a matter of fact, a complete factorial design was used to determine the effect of residence time (X₁), plant density (X₂) and initial chemical oxygen demand (COD) concentration (X₃) on the phytoremediation process. The process's performance was measured on COD (Y₁), NH₄⁺ (Y₂) and PO₄^3- (Y₃), with the results indicating a reduction of 8.59-81.71% of COD (Y₁); 22.53-95.81% of NH₄⁺ (Y₂) and 0.54-99.35% of PO₄^3- (Y₃). Then, the first-order models obtained for COD, NH₄⁺ and PO₄^3- removal were validated using different statistical approaches such as statistical and experimental validation. Moreover, multi-response optimization was carried out through different scenarios. On the whole, the results obtained indicated that two serial ponds are required for an optimum organic matter removal by Eichhornia crassipes. Indeed, for the first pond, a residence time of 15 days is needed with a plant density of 60 ft/m² and an initial concentration of about 944 mg/L. The second was the same residence time as the first with similar plant density of 60 ft/m² and an initial load 192 mg/L (> 200 mg/L). Optimal organic matter removal from wastewater using Eichhornia crassipes requires two ponds arranged in chain.

Activation of persulfate by homogeneous and heterogeneous iron catalyst to degrade chlortetracycline in aqueous solution

This study investigates the removal of chlortetracycline (CTC) antibiotic using sulfate radical-based oxidation process. Sodium persulfate (PS) was used as a source to generate sulfate radicals by homogeneous (Fe²⁺) and heterogeneous (zero valent iron, ZVI) iron as a catalyst. Increased EDTA concentration was used to break the CTC-Fe metal complexes during CTC estimation. The influence of various parameters, such as PS concentration, iron (Fe²⁺ and ZVI) concentration, PS/iron molar ratio, and pH were studied and optimum conditions were reported. CTC removal was increased with increasing concentration of PS and iron at an equal molar ratio of PS/Fe²⁺ and PS/ZVI processes. PS/Fe²⁺ and PS/ZVI oxidation processes at 1:2 (500 μM PS and 1000 μM) molar ratio showed 76% and 94% of 1 μM CTC removal in 2 h. Further increased molar ratio 1:2 onwards, PS/Fe²⁺ process showed a slight increase in CTC degradation whereas in PS/ZVI process showed similar degradation to 1:2 (PS/Fe) ratio at constant PS 500 μM concentration. Slower activation of persulfate which indirectly indicates the slower generation of sulfate radicals in PS/ZVI process showed higher degradation efficiency of CTC. The detected transformation products and their estrogenicity results stated that sulfate radicals seem to be efficient in forming stable and non-toxic end products.