Microbiological and physicochemical quality enhancement of treated wastewater using raw and chemically modified clays from Sidi Bouzid region, Tunisia.

Environmental discharge of wastewater represents a source of chemical and biological pollutants. This study firstly evaluates the microbiological and physicochemical quality of treated wastewaters collected from two wastewater treatment plants (WWTPs) located in two different Tunisian cities namely Sidi Bouzid (SB) and Gafsa (G). Then, the capacity of three raw and acid/base-activated local clays to enhance the quality of wastewaters was assessed. The results indicate that the quantities of enteric bacteria (oscillating from 1.381 × 103 to 1.4 × 108 CFU/100 mL), fungi (between 1.331 × 103 and 1.781 × 104 CFU/100 mL), as well as SARS-CoV-2 (between 4.25 × 103 and 5.05 × 105 CFU/100 mL) and Hepatitis A virus RNA (form 4.25 × 103 to 7.4 × 104 CFU/100 mL) detected in effluent wastewaters were not in compliance with the Tunisian standards for both studied WWTPs. Likewise for other indicators such as electrical conductivity (ranging 4.9-5.4 mS/cm), suspended matter (145-160 g l-1), chemical oxygen demand (123-160 mg l-1), biological oxygen demand 5 (172-195 mg l-1), chloride, Total Kjeldahl nitrogen (TKN) and phosphorus contents (710, 58-66 and 9.47-10.83 mg l-1 respectively), the registered values do not agree with the set standards established for wastewater treatment. On the other hand, the pH values fitted (oscillating from 6.86 (at G) to 7.24 (at SB) with the Tunisian standards for both WWTPs. After treatment, wastewaters showed better values for the microbiological parameters, especially for the clays designed as AM and HJ1, which eliminated 100% of viruses. In addition, when acid-activated AM clays were applied, a marked improvement in the quality of physicochemical parameters was obtained, especially for suspended matter (2 and 4 g l-1 for SB and G, respectively), TKN (5.2 (SB) and 6.40 (G) mg/l), phosphorus (1.01 (SB) and 0.81 (G) mg/l). Our results open perspectives for the possibility of efficiently using these specific clays in the enhancement of the quality of treated wastewaters.

Analysis of LoRaWAN 1.0 and 1.1 Protocols Security Mechanisms.

LoRaWAN is a low power wide area network (LPWAN) technology protocol introduced by the LoRa Alliance in 2015. It was designed for its namesake features: long range, low power, low data rate, and wide area networks. Over the years, several proposals on protocol specifications have addressed various challenges in LoRaWAN, focusing on its architecture and security issues. All of these specifications must coexist, giving rise to the compatibility issues impacting the sustainability of this technology. This paper studies the compatibility issues in LoRaWAN protocols. First, we detail the different protocol specifications already disclosed by the LoRa Alliance in two major versions, v1.0 and v1.1. This is done through presenting two scenarios where we discuss the communication and security mechanisms. In the first scenario, we describe how an end node (ED) and network server (NS) implementing LoRaWAN v1.0 generate session security keys and exchange messages for v1.0. In the second scenario, we describe how an ED v1.1 and an NS v1.1 communicate after generating security session keys. Next, we highlight the compatibility issues between the components implementing the two different LoRaWAN Specifications (mainly v1.0 and v1.1). Next, we present two new scenarios (scenarios 3 and 4) interchanging the ED and NS versions. In scenario three, we detail how an ED implementing LoRaWAN v1.1 communicates with an NS v1.0. Conversely, in scenario four, we explain how an ED v1.0 and an NS v1.1 communicate. In all these four scenarios, we highlight the concerns with security mechanism: show security session keys are generated and how integrity and confidentiality are guaranteed in LoRaWAN. At the end, we present a comparative table of these four compatibility scenarios.

A novel bioprocess combining anaerobic co-digestion followed by ultra-filtration and microalgae culture for optimal olive mill wastewater treatment.

Treatment of olive mill wastewater (OMW) has received considerable research globally due to its influence on the technical, economic, and environmental sustainability of wastewater biogas production. This work presents a novel combined biological process for OMW treatment in terms to produce for the first time, treated OMW and a valuable microalgae biomass. The process involves anaerobic co-digestion (AD), a low cut-off membrane ultra-filtration (UF) and a subsequent Scenedesmus sp. culture. The AD of OMW was conducted at high initial COD ranging from 28 to 38 g/L using an up-flow anaerobic fixed bed bio-reactor (300 L). Results revealed that the maximum biogas production was about 0.507 L/g CODintroduced.day containing 73% of methane corresponding to a methane yield of 0.370 L/g CODintroduced.day obtained at an organic loading rate of 4.58 g COD/L.day. High removal levels of COD, total phenolic compounds, and total suspended solids in the anaerobic liquid digestate (ALD) were achieved after AD and UF. Scenedesmus sp. was then cultivated on the ultra-filtrated ALD. A maximum biomass productivity of 0.15 g/L.day was recorded when Scenedesmus sp. is grown on 25% of ultra-filtrated ALD with a maximum nitrogen removal rate of 15.18 mg/L.day and an almost total elimination of phosphorus and phenolic compounds.

Anaerobic biological treatment of industrial saline wastewater: fixed bed reactor performance and analysis of the microbial community structure and abundance.

The purpose of the present work is to treat saline Tuna fish wastewater, with the salt concentration of 43 g L-1 and total organic carbon (TOC) of 8.3 g L-1, using an anaerobic fixed bed reactor involving salt-tolerant bacteria from the natural hypersaline environment during 150 days. The highest volatile solids (VS) removal efficiency of 84.1% was recorded for the organic loading rate (OLR) of 1.04 g TOC L-1.d-1 and the lowest salinity of 14.6 g NaCl L-1. In addition, the maximum biogas production of 0.8 L-1.d-1 for a working volume of 4 L and an organic loading rate of 2.07 g TOC L-1.d-1 correlated with the decrease of Volatile fatty acids (VFA) content. The Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) and the phylogenetic analysis of the bacterial community showed the action of hydrolytic, acidogenic, halotolerant sulfate-reducing and halophilic fermentative bacterium during the processing time. A stable archaeal and methanogenic community's diversity including hydrogenotrophic methanogens was demonstrated with Quantitative-PCR (Q-PCR). The highest bacterial population abundance was detected for 1.45 g TOC L-1.d-1 and the important methanogenic community abundance for 2.07 g TOC L-1.d-1 may be related to the highest biogas production in this charge for an effluent salinity of 27.7 g NaCl L-1.

Comparison between Thermo-Alkaline and Electro-Fenton Disintegration Effect on Waste Activated Sludge Anaerobic Digestion.

Disintegration of municipal waste activated sludge (WAS) using thermo-alkaline (TA) and electro-Fenton (EF) methods was investigated and compared in terms of the efficiency of sludge solubilisation and enhancement of anaerobic biodegradability. Performance of organic matter solubilisation (soluble COD, proteins, polysaccharides) of sludge pretreated with EF was proved to be better than that with TA pretreatment, which resulted in the enhancement of anaerobic biodegradability. Comparison of results indicated that percentages of PN and PS release obtained after EF pretreatment (68.95 and 65.22%) were higher than those obtained by TA method (45.25 and 35.22%) respectively. An improvement of biogas potential about 2 and 1.6 times was achieved respectively by EF and TA pretreatment in comparison to raw sludge. During semi-continuous fermentation study in continuous stirred tank reactor, EF pretreated sludge gave the best biogas yield (0.6 L biogas/g COD) at an OLR of 2.5 g COD/L. d in comparison to TA pretreated sludge (0.3 L biogas/g COD), where low biogas yield about 0.1 L biogas/g COD was registered by raw sludge in the same CSTR. Therefore, the integration of EF process to anaerobic digestion might be a promising process for sludge reduction and biogas recovery.

Effect of bacterial lipase on anaerobic co-digestion of slaughterhouse wastewater and grease in batch condition and continuous fixed-bed reactor.

BACKGROUND: This study aimed to investigate the effects of bacterial lipase on biogas production of anaerobic co-digestion of slaughterhouse wastewater (SHWW) and hydrolyzed grease (HG). A neutrophilic Staphylococcus xylosus strain exhibiting lipolytic activity was used to perform microbial hydrolysis pretreatment of poultry slaughterhouse lipid rich waste. RESULTS: Optimum proportion of hydrolyzed grease was evaluated by determining biochemical methane potential. A high biogas production was observed in batch containing a mixture of slaughterhouse composed of 75% SHWW and 25% hydrolyzed grease leading to a biogas yield of 0.6 L/g COD introduced. Fixed bed reactor (FBR) results confirmed that the proportion of 25% of hydrolyzed grease gives the optimum condition for the digester performance. Biogas production was significantly high until an organic loading rate (OLR) of 2 g COD/L. d. CONCLUSION: This study indicates that the use of biological pre-treatment and FBR for the co-digestion of SHWW and hydrolyzed grease is feasible and effective.

Anaerobic co-digestion of Tunisian green macroalgae Ulva rigida with sugar industry wastewater for biogas and methane production enhancement.

Ulva rigida is a green macroalgae, abundantly available in the Mediterranean which offers a promising source for the production of valuable biomaterials, including methane. In this study, anaerobic digestion assays in a batch mode was performed to investigate the effects of various inocula as a mixture of fresh algae, bacteria, fungi and sediment collected from the coast of Sfax, on biogas production from Ulva rigida. The results revealed that the best inoculum to produce biogas and feed an anaerobic reactor is obtained through mixing decomposed macroalgae with anaerobic sludge and water, yielding into 408mL of biogas. The process was then investigated in a sequencing batch reactor (SBR) which led to an overall biogas production of 375mL with 40% of methane. Further co-digestion studies were performed in an anaerobic up-flow bioreactor using sugar wastewater as a co-substrate. A high biogas production yield of 114mL g-1 VSadded was obtained with 75% of methane. The co-digestion proposed in this work allowed the recovery of natural methane, providing a promising alternative to conventional anaerobic microbial fermentation using Tunisian green macroalgae. Finally, in order to identify the microbial diversity present in the reactor during anaerobic digestion of Ulva rigida, the prokaryotic diversity was investigated in this bioreactor by the denaturing gradient gel electrophoresis (DGGE) method targeting the 16S rRNA gene.

Biodegradation of fluoranthene by a newly isolated strain of Bacillus stratosphericus from Mediterranean seawater of the Sfax fishing harbour, Tunisia.

A physico-chemical characterization of seawater taken from the fishing harbour of Sfax, Tunisia, revealed a contamination by organic and inorganic micropollutants. An aerobic marine halotolerant Bacillus stratosphericus strain FLU5 was isolated after enrichment on fluoranthene, a persistent and toxic polycyclic aromatic hydrocarbon (PAH). GC-MS analyses showed that strain FLU5 was capable of degrading almost 45 % of fluoranthene (100 mg l(-1)), without yeast extract added, after 30 days of incubation at 30 g l(-1) NaCl and 37 °C. In addition, the isolate FLU5 showed a remarkable capacity to grow on a wide range of aliphatic, aromatic and complex hydrocarbons. This strain could also synthesize a biosurfactant which was capable of reducing the surface tension of the cell-free medium, during the growth on fluoranthene. The biodegradative abilities of PAHs are promising and can be used to perform the bioremediation strategies of seawaters and marine sediments contaminated by hydrocarbons.

Treatment of textile wastewater by submerged membrane bioreactor: In vitro bioassays for the assessment of stress response elicited by raw and reclaimed wastewater.

The performance of a pilot-scale membrane bioreactor (MBR) system for the treatment of textile wastewater was investigated. The MBR was continuously operated for 7 months. Very high treatment efficiencies were achieved (color, 100%; chemical oxygen demand (COD), 98%; biochemical oxygen demand (BOD5), 96%; suspended solids (SS), 100%). Furthermore, the MBR treatment efficiency was analyzed from a toxicological-risk assessment point of view, via different In vitro bioassays using Caco-2 cells, a widely used cell model in toxicological studies. Results showed that MBR treatment significantly reduced the raw textile wastewater (RTWW) cytotoxicity on Caco-2 cells by 53% for a hydraulic retention time (HRT) of 2 days. Additionally, the RTWW-induced disruption in the barrier function (BF) of the Caco-2 cell monolayer was also significantly reduced after MBR treatment under a HRT of 2 days (no disruption of BF was observed). Moreover, the effect of RTWW and treated wastewater on stress response was investigated using different stress genes: AHSA1, HSPD1, HSPA1A, HSPA5 and HSPA8. The cell exposure to RTWW significantly increased the expression of all used stress genes; interestingly, the treated wastewater (HRT 2 days) did not show any significant modulation of the stress genes.

Improvement of anaerobic digestion of waste-activated sludge by using H2O2 oxidation, electrolysis, electro-oxidation and thermo-alkaline pretreatments.

Disintegration of municipal waste-activated sludge (WAS) is regarded as a prerequisite of the anaerobic digestion process to reduce sludge volume and improve biogas yield. Pretreatment of WAS using thermo-alkaline (TA), H2O2 oxidation, electrolysis and electro-oxidation (EO) processes were investigated and compared in term of COD solubilization and biogas production. For each pretreatment, the influences of different operational variables were studied in detail. At optimum conditions, EO gave the maximum COD solubilization (28 %). The effects of pretreatments under the optimum conditions on anaerobic digestion were experienced with biochemical methane potential assay. Significant increases in biogas yield up to 78 and 40 % were observed respectively in the EO and TA pretreated samples compared to raw sludge. Results clearly revealed that the application of EO is a significant alternative method for the improvement of WAS anaerobic digestion.

Biological treatment of fish processing wastewater: A case study from Sfax City (Southeastern Tunisia).

The present work presents a study of the biological treatment of fish processing wastewater at salt concentration of 55 g/L. Wastewater was treated by both continuous stirred-tank reactor (CSTR) and membrane bioreactor (MBR) during 50 and 100 days, respectively. These biological processes involved salt-tolerant bacteria from natural hypersaline environments at different organic loading rates (OLRs). The phylogenetic analysis of the corresponding excised DGGE bands has demonstrated that the taxonomic affiliation of the most dominant species includes Halomonadaceae and Flavobacteriaceae families of the Proteobacteria (Gamma-proteobacteria class) and the Bacteroidetes phyla, respectively. The results of MBR were better than those of CSTR in the removal of total organic carbon with efficiencies from 97.9% to 98.6%. Nevertheless, salinity with increasing OLR aggravates fouling that requires more cleaning for a membrane in MBR while leads to deterioration of sludge settleability and effluent quality in CSTR.

Anaerobic membrane bioreactor for the treatment of leachates from Jebel Chakir discharge in Tunisia.

Landfill leachate (LFL) collected from the controlled discharge of Jebel Chakir in Tunisia was treated without any physical or chemical pretreatment in an anaerobic membrane bioreactor (AnMBR). The organic loading rate (OLR) in the AnMBR was gradually increased from 1 g COD l(-1)d(-1) to an average of 6.27 g COD l(-1)d(-1). At the highest OLR, the biogas production was more than 3 volumes of biogas per volume of the bioreactor. The volatile suspended solids (VSSs) reached a value of approximately 3 g l(-1) in the bioreactor. At stable conditions, the treatment efficiency was high with an average COD reduction of 90% and biogas yield of 0.46 l biogas per g COD removed.

Application of combined membrane biological reactor and electro-oxidation processes for the treatment of landfill leachates.

Landfill leachate (LFL) is a very complex wastewater that poses considerable hazards to local communities and the environment. With this concern in mind, the present study was undertaken to investigate the performance of an aerobic membrane bioreactor treating raw LFL from Djebel Chekir (Tunisia) discharge. The LFL samples collected from this site were found to be highly loaded with organic matter, ammonia, salts, greases, phenols and hydrocarbons. Important removals of chemical oxygen demand (COD) and NH4+-N were attained after 44 days of treatment at optimum conditions for the membrane and with organic loading rates (OLR) of 1.9 and 2.7 grams COD per litter and day. This treatment allowed for an important detoxification of the landfill leachates and a significant elimination of the microorganisms. Electrochemical oxidation using Pi/Ti was applied as a post-treatment and after the biological process in order to reduce the residual ammonia and COD. At a pH value of 9, current density of 4 A dm(-2) and electrolysis time of 60 minutes, COD and ammonia nitrogen were reduced to 1,000 mg L(-1) and 27 mg L(-1), respectively. COD and NH4+-N removals were accompanied by significant detoxification.