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.

Degradation of Chloramphenicol in Synthetic and Aquaculture Wastewater Using Electrooxidation.

Chloramphenicol (CAP) is a broad-spectrum antibiotic widely used in animal farming and aquaculture industries. Despite its ban in many countries around the world, it is still used in several developing countries, with harmful effects on the surrounding aquatic environment. In this study, an electrooxidation process using a Ti/PbO anode was used to investigate the degradation of CAP in both synthetic solution and real aquaculture wastewater. A central composite design was used to determine the optimum conditions for CAP removal. Current intensity and treatment time had the most impact on the CAP removal. These two factors accounted for ∼90% of CAP removal. The optimum conditions found in this study were current intensity of 0.65 A, treatment time of 34 min, and CAP initial concentration of 0.5 mg L. Under these conditions, 98.7% of CAP removal was achieved with an energy consumption of 4.65 kW h m. The antibiotic was not present in the aquaculture wastewater, which received 0.5 mg L of CAP and was treated (by electrooxidation) under the optimum conditions. A complete removal of CAP was obtained after 34 min of treatment. According to these results, electrooxidation presents an option for the removal of antibiotics, secondary compounds, and other organic and inorganic compounds from solution.

Techno-economic evaluation of simultaneous production of extra-cellular polymeric substance (EPS) and lipids by Cloacibacterium normanense NK6 using crude glycerol and sludge as substrate.

This study used the technical, economic analysis tool, SuperPro designer in evaluating a novel technology for simultaneous production of extracellular polymeric substance (EPS) and biodiesel using crude glycerol and secondary sludge. As renewable energy sources are depleting, the process utilizes municipal sewage sludge for production of EPS and biodiesel along with crude glycerol, which is a waste byproduct of biodiesel industry providing an alternate way for disposal of municipal sludge and crude glycerol. Newly isolated Cloacibacterium normanense NK6 is used as micro-organism in the study as it is capable of producing high EPS concentration, using activated sludge and crude glycerol as the sole carbon source. The technology has many environmental and economic advantages like the simultaneous production of two major products: EPS and lipids. Sensitivity analysis of the process revealed that biomass lipid content is a most significant factor where unit cost production of biodiesel was highly sensitive to lipid content during bioreaction. B7 biodiesel unit production cost can be lowered from $1 to $0.6 if the lipid content of the biomass is improved by various process parameter modifications.

Electrochemical removal of carbamazepine in water with Ti/PbO2 cylindrical mesh anode.

Carbamazepine (CBZ) is one of the most frequently detected organic compounds in the aquatic environment. Due to its bio-persistence and toxicity for humans and the environment its removal has become an important issue. The performance of the electrochemical oxidation process and in situ production of reactive oxygen species (ROS), such as O3 and H2O2, for CBZ removal have been studied using Ti/PbO2 cylindrical mesh anode in the presence of Na2SO4 as supporting electrolyte in a batch electrochemical reactor. In this integrated process, direct oxidation at anode and indirect oxidation by in situ electrogenerated ROS can occur simultaneously. The effect of several factors such as electrolysis time, current intensity, initial pH and oxygen flux was investigated by means of an experimental design methodology, using a 2(4) factorial matrix. CBZ removal of 83.93% was obtained and the most influential parameters turned out to be electrolysis time, current intensity and oxygen flux. Later, the optimal experimental values for CBZ degradation were obtained by means of a central composite design. The best operating conditions, analyzed by Design Expert(®) software, are the following: 110 min of electrolysis at 3.0 A, pH = 7.05 and 2.8 L O2/min. Under these optimal conditions, the model prediction (82.44%) fits very well with the experimental response (83.90 ± 0.8%). Furthermore, chemical oxygen demand decrease was quantified. Our results illustrated significant removal efficiency for the CBZ in optimized condition with second order kinetic reaction.

Surfactants in aquatic and terrestrial environment: occurrence, behavior, and treatment processes.

Surfactants belong to a group of chemicals that are well known for their cleaning properties. Their excessive use as ingredients in care products (e.g., shampoos, body wash) and in household cleaning products (e.g., dishwashing detergents, laundry detergents, hard-surface cleaners) has led to the discharge of highly contaminated wastewaters in aquatic and terrestrial environment. Once reached in the different environmental compartments (rivers, lakes, soils, and sediments), surfactants can undergo aerobic or anaerobic degradation. The most studied surfactants so far are linear alkylbenzene sulfonate (LAS), quaternary ammonium compounds (QACs), alkylphenol ethoxylate (APEOs), and alcohol ethoxylate (AEOs). Concentrations of surfactants in wastewaters can range between few micrograms to hundreds of milligrams in some cases, while it reaches several grams in sludge used for soil amendments in agricultural areas. Above the legislation standards, surfactants can be toxic to aquatic and terrestrial organisms which make treatment processes necessary before their discharge into the environment. Given this fact, biological and chemical processes should be considered for better surfactants removal. In this review, we investigate several issues with regard to: (1) the toxicity of surfactants in the environment, (2) their behavior in different ecological systems, (3) and the different treatment processes used in wastewater treatment plants in order to reduce the effects of surfactants on living organisms.

Occurrence, fate and effects of Di (2-ethylhexyl) Phthalate in wastewater treatment plants: a review.

Phthalates, such as Di (2-ethylhexyl) Phthalate (DEHP) are compounds extensively used as plasticizer for long time around the world. Due to the extensive usage, DEHP is found in many surface waters (0.013-18.5 µg/L), wastewaters (0.716-122 µg/L), landfill leachate (88-460 µg/L), sludge (12-1250 mg/kg), soil (2-10 mg/kg). DEHP is persistent in the environment and the toxicity of the byproducts resulting from the degradation of DEHP sometime exacerbates the parent compound toxicity. Water/Wastewater treatment processes might play a key role in delivering safe, reliable supplies of water to households, industry and in safeguarding the quality of water in rivers, lakes and aquifers. This review addresses state of knowledge concerning the worldwide production, occurrence, fate and effects of DEHP in the environment. Moreover, the fate and behavior of DEHP in various treatment processes, including biological, physicochemical and advanced processes are reviewed and comparison (qualitative and quantitative) has been done between the processes. The trends and perspectives for treatment of wastewaters contaminated by DEHP are also analyzed in this review.

Photosonochemical degradation of butyl-paraben: optimization, toxicity and kinetic studies.

The objective of the present work is to evaluate the potential of a photosonolysis process for the degradation of butyl-paraben (BPB). After 120 min of treatment time, high removal of BPB was achieved by the photosonolysis (US/UV) process (88.0±0.65%) compared to the photochemical (UV) and the conventional ultrasonication (US) processes. Several factors such as calorimetric power, treatment time, pH and initial concentration of BPB were investigated. Using a 2(4) factorial matrix, the treatment time and the calorimetric power are the main parameters influencing the degradation rate of BPB. Subsequently, a central composite design methodology has been investigated to determine the optimal experimental parameters for BPB degradation. The US/UV process applied under optimal operating conditions (at a calorimetric power of 40 W during 120 min and under pH7) is able to oxidize around 99.2±1.4% of BPB and to record 43.3% of mineralization. During the US/UV process, BPB was mainly transformed into 1 hydroxy BPB, dihydroxy BPB, hydroquinone and 4-hydroxybenzoic acid. Microtox biotests (Vibrio fisheri) showed that the treated effluent was not toxic. The pseudo-first order kinetic model (k=0.0367 min(-1)) described very well the oxidation of BPB.

Photocatalytic degradation of carbamazepine in wastewater by using a new class of whey-stabilized nanocrystalline TiO2 and ZnO.

Nanoscale photocatalysts have attracted much attention due to their high surface area to volume ratios. However, due to extremely high reactivity, TiO2 and ZnO nanoparticles prepared using different methods tend to either react with surrounding media or agglomerate, resulting in the formation of much larger flocs and significant loss in reactivity. This work investigates the photocatalytic degradation of carbamazepine (CBZ), a persistent pharmaceutical compound from wastewater (WW) using TiO2 and ZnO nanoparticles prepared in the presence of a water-soluble whey powder as stabilizer. The TiO2 and ZnO nanoparticles prepared in the presence of whey stabilizer displayed much less agglomeration and greater degradation power than those prepared without a stabilizer. Higher photocatalytic degradation of carbamazepine was observed (100%) by using whey stabilized TiO2 nanoparticles with 55 min irradiation time as compared to ZnO nanoparticles (92%). The higher degradation of CBZ in wastewater by using TiO2 nanoparticles as compared to ZnO nanoparticles was due to formation of higher photo-generated holes with high oxidizing power of TiO2. The photocatalytic capacity of ZnO anticipated as similar to that of TiO2 as it has the same band gap energy (3.2 eV) as TiO2. However, in the case of ZnO, photocorrosion frequently occurs with the illumination of UV light and this phenomenon is considered as one of the main reasons for the decrease of ZnO photocatalytic activity in aqueous solutions. Further, the estrogenic activity of photocatalyzed WW sample with CBZ and its by-products was carried out by yeast estrogen screen (YES) assay method. Based upon the YES test results, none of the samples showed estrogenic activity.

Photoelectrocatalytic degradation of carbamazepine using Ti/TiO2 nanostructured electrodes deposited by means of a pulsed laser deposition process.

The objective of the present work is to evaluate the potential of photoelectrocatalytic oxidation (PECO) process using Ti/TiO2 for the degradation of carbamazepine (CBZ). Ti/TiO2 prepared by pulsed laser deposition (PLD) has been used as a photo-catalyst in a photoelectrocatalytic cell. The PLD TiO2 coatings were found to be of anatase structure consisting of nanocrystallites of approximately 15nm in diameter. Factorial and central and extreme composite design methodologies were successively employed to define the optimal operating conditions for CBZ degradation. Several factors such as current intensity, treatment time, pollutant concentration and cathode material were investigated. Using a 2(4) factorial matrix, the best performance for CBZ degradation (53.5%) was obtained at a current intensity of 0.1 A during 120min of treatment time and when the vitreous carbon (VC) was used at the cathode in the presence of 10mgL(-1) of CBZ. Treatment time and pollutant concentration were found to be very meaningful for CBZ removal. The PECO process applied under optimal conditions (at current intensity of 0.3A during 120min in the presence of 10mgL(-1) of CBZ with VC at the cathode) is able to oxidize around 73.5% ±2.8% of CBZ and to ensure 21.2%±7.7% of mineralization. During PECO process, CBZ was mainly transformed to acridine and anthranilic acid. Microtox biotests (Vibrio fisheri) showed that the treated - effluent was not toxic. The pseudo-second order kinetic model (k2=6×10(-4)Lmg(-1)min(-1)) described very well the oxidation of CBZ.

Di 2-ethylhexylphtalate in the aquatic and terrestrial environment: a critical review.

Phthalates are being increasingly used as softeners-plasticizers to improve the plasticity and the flexibility of materials. Amongst the different plasticizers used, more attention is paid to di (2-ethylhexylphtalate) (DEHP), one of the most representative compounds as it exhibits predominant effects on environment and human health. Meanwhile, several questions related to its sources; toxicity, distribution and fate still remain unanswered. Most of the evidence until date suggests that DEHP is an omnipresent compound found in different ecological compartments and its higher hydrophobicity and low volatility have resulted in significant adsorption to solids matrix. In fact, there are important issues to be addressed with regard to the toxicity of this compound in both animals and humans, its behavior in different ecological systems, and the transformation products generated during different biological or advanced chemical treatments. This article presents detailed review of existing treatment schemes, research gaps and future trends related to DEHP.

[Treatment of PAH-contaminated aluminium wastes by flotation using amphoteric surfactants]. / Traitement de dechets d'aluminerie contamines en hap par flottation en presence de surfactants amphoteres.

The aluminium industry produces wastes polluted with polycyclic aromatic hydrocarbons (PAH). The most important PAH found in these wastes is benzo(b,j,k)fluoranthene (BJK) at concentrations exceeding the permitted levels (>1000 mg kg(-1)). The objective of this research was to compare the performances of amphoteric (BW and CAS) and non-ionic surfactants (Triton X-100 and Tween 80), at a concentration of 0.5% (w w(-1)), for PAH removal (and particularly for BJK) during washing treatment of aluminium industry wastes. The best removal yield of BJK (35%) has been measured during treatment with CAS. The efficiency of this surfactant has been further improved by using a flotation process. Flotation tests have also been realized at different CAS concentrations (0.1, 0.2, 0.25 and 0.5% w w(-1)) and using different total solids (7, 10, 15 and 20% w v(-1)). The highest BJK removal yield (68%) has been obtained using 0.5% CAS and a total solids concentration of 15%. The rate of hazardous wastes produced in these conditions represents 10% of the initial weight of aluminium wastes treated.

Removal of metals in leachate from sewage sludge using electrochemical technology.

Heavy metals in acidic leachates from sewage sludge are usually removed by chemical precipitation, which often requires high concentration of chemicals and induces high metallic sludge production. Electrochemical technique has been explored as an alternative method in a laboratory pilot scale reactor for heavy metals (Cu and Zn) removal from sludge leachate. Three electrolytic cell arrangements using different electrodes materials were tested: mild steel or aluminium bipolar electrode (EC cell), Graphite/stainless steel monopolar electrodes (ER cell) and iron-monopolar electrodes (EC-ER cell). Results showed that the best performances of metal removal were obtained with EC and EC-ER cells using mild steel electrodes operated respectively at current intensities of 0.8 and 2.0 A through 30 and 60 min of treatment. The yields of Cu and Zn removal from leachate varied respectively from 92.4 to 98.9% and from 69.8 to 76.6%. The amounts of 55 and 44 kg tds(-1) of metallic sludge were respectively produced using EC and EC-ER cells. EC and EC-ER systems involved respectively a total cost of 21.2 and 13.1 CAN dollars per ton of dry sludge treated including only energy consumption and metallic sludge disposal. The treatment using EC-ER system was found to be effective and more economical than the traditional metal precipitation using either Ca(OH)2 and/or NaOH.

[Bioleaching kinetic of a pyrite mining residue using organic wastes as culture media for Acidithiobacillus ferrooxidans]. / Cinétique de biolixiviation d'un résidu minierde pyrite en présence d'effluents organiquesutilisés comme milieu de culture pour Acidithiobacillus ferrooxidans.

In this study, the results of the leaching of metal sulphide concentrate using organic wastes as culture media for Acidithiobacillus ferrooxidans are summarized. These results indicate that the liquid fraction of municipal sewage sludge, paper mill sludge and pig manure, containing 10% (w v(-1)) pulp density of a pyritic mine waste concentrate can support the growth of the leaching bacteria and allow metal solubilization. The inhibition by dissolved organic carbon (DOC) appeared when the concentration in pig manure liquid fraction and sewage sludge filtrate is higher than 180 mg l(-1) and 500 mg l(-1), respectively. However, increase in organic concentration up to 650 mg l(-1) using paper mill sludge supernatant had no inhibitory effect on the bacterial growth. An important decrease of the DOC has been measured during all bioleaching tests. The organic matter was probably consumed by heterotrophic microorganisms activity. The growth rate of the iron-oxidizing bacteria varied from 0.05 to 0.07 h(-1). The dissolution of pyrite (FeS2) in organic waste media led to a yield of Fe solubilization of about 35%. Copper and zinc were also solubilized during the bioleaching tests. The yields of Cu and Zn solubilization ranged from 12 to 24%.

Oxidising and disinfecting by hydrogen peroxide produced in a two-electrode cell.

Hydrogen peroxide was produced by direct current electrolysis using two electrodes only, a carbon felt cathode and a dimensional stabilised anode (titanium coated with RuO2), without adding any chemical. The required oxygen was supplied by water oxidation and by transfer from the atmosphere. The intensity should be maintained under a maximum value to avoid peroxide reduction. High peroxide production rate and concentration were then reached. Electroperoxidation partially removed dissolved organic carbon (DOC) contained in solutions of phenol, salicylic acid, benzoic acid and humic acids. The DOC removal in effluent of municipal sewage plant corresponded to a breakage of the double bonds. Real effluents were significantly disinfected owing to the direct effect of electric current and the indirect effect of peroxide. Moreover, a remnant effect was ensured.