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Several mathematical models are developed to explain microorganism responses to ultraviolet irradiation. During this study, Pseudomonas aeruginosa was taken as a microorganism model. The experimental results obtained during a batch UV-reactor established that the disinfection kinetics is far from being uniform over the batch. Application of the first-order Chick-Watson model, in its original form or modified form, to validate the speed changes over the disinfection process, does not report any significantly improved results. Application of the Collins-Selleck model fits better the kinetic curves of UV disinfection of wastewater for all the tested strains of P. aeruginosa. At the same time, various continuous alternative reactors are checked, by accounting for the fluid flow hydrodynamics, that is, a perfectly mixing reactor without and with short circuits in the flow stream, or without and with dead zone inside the reactor, a plug flow reactor, and a series of perfectly mixed reactors. The results indicate that the succession of 4 perfectly mixed reactors is the best alternative to the process scale-up. Key words: Disinfection, hydrodynamics, kinetics model, reactor of disinfection, treated wastewater, UV radiation.

The aim of this paper was to propose a modeling system of water ultraviolet (UV) disinfection. Results reveal that application of the model of Chick-Watson in its original form or modified are not representative of the kinetics of disinfection. For this reason, the application of a new kinetic model of Collins-Selleck in UV inactivation of Pseudomonas aeruginosa in secondary wastewater appeared to be the best applied model. The modeling of the reactivation process at range of 7.5-50°C temperature was shown. First-order saturation does not fit the obtained data in photoreactivation; a modification of the model is proposed coinciding with the classical logistic equation. To better explain the process of inactivation, we have assumed that the action of disinfectant on the survival of lonely microorganisms is faster than its action on suspended solids protected or agglomerated to each other. For this reason, the application of a new kinetic model by introducing a third factor reflecting the influence of suspended solids in water on disinfection kinetics appeared to be determinant for modeling UV inactivation of P. aeruginosa in secondary treated wastewater. Key words: Secondary wastewater, ultraviolet (UV) disinfection, modeling, photoreactivation. Pseudomonas aeruginosa, suspended solids.

The purpose of this research stream is to evaluate the kinetics of bacterial strains of Pseudomonas aeruginosa, to establish the influence of UV doses on the kinetics of disinfection, to study UV-resistant strains of Pseudomonas aeruginosa, and to underline the influence of suspended solids on the inactivation kinetics of these strains. Furthermore, and due to the lack of readily available information about the influence of temperature on microorganism inactivation processes subsequent to inactivation with UV radiation, a series of batch studies were performed at 5℃, 25?C, 37.5℃ and 50℃. This paper investigates the impact of UV irradiation on bacterial strains of P. aeruginosa inactivation in both primary and secondary wastewater effluents and to show the influence of filtration in the process of disinfection of water by UV irradiaton. Our results indicate that the effect of temperature within the normal operating range of most treatment plants, i.e., 25℃ to 37.5℃, was found to be not statistically significant on the kinetics of the UV disinfection process. However, the kinetics of the UV disinfection process was highly affected by system operating at extreme temperatures, i.e., at 10 and 50℃. In a temperature range of 25℃ to 37.5℃, the inactivation of P. aeruginosa strains varied according to the incubation time and did not exceed 4 U-Log. Consequently, having more than 102 organisms/100ml of P. aeruginosa in treated wastewater would cause serious health and environmental problems. Low inactivation was observed when the operating temperature was reduced to 10℃ regardless of the incubation time tested. In contrast, a considerable increase in the inactivation rate was noted when the temperature of the disinfected wastewater was increased to 50℃. Hence, as 5℃ and 50℃ are outside the operating range of most treatment plants, as in our country, Tunisia, it is reasonable to assume that the effect of temperature change on the kinetics of UV disinfection process is negligible.

In order to test the ability to produce antibacterial substances within marine bacteria, prior to select potential probiotics for use in shellfish farming, we targeted a large collection of bacterial isolates (132 strains), brought from the clamRuditapes decussatus and 37 reference strains. First, we proceeded to their biochemical identification and the screening of antibiotic resistance profiles. Else, we investigated their inhibitory activityin vitro against several fish and shellfish pathogens, using two methods: the double-layer agar and the direct simultaneous antagonism methods. The results showed high frequencies of inhibitory producing bacteria (IPB) within the isolates. These bacteria (25%) were aerobic mesophylic bacteria belonging to various bacterial groups: 33.7% oxidase-positive Gram-negative bacteria, 7.4%Enterobacteriaceae and 28% lactic acid bacteria. Besides this group, nine strains produced strong inhibition effect. These bacteria belonged to:Aeromonas hydrophila, Aeromonas sobria, Pseudomonas cepacia, Vibrio sp,Serratia liquefaciens andLactobacillus rhamnosus. They were active against pathogenic bacteria belonging to the genera:Aeromonas, Pseudomonas andVibrio. These potential probiotics were submitted to further investigations prior to their introduction in larval shellfish farming.

Ultraviolet irradiation (UV-C) is proven to be effective to inactivate microorganisms. The present study investigates the effect of sublethal UV-C rays on the membrane fatty acid profile of four Staphylococcus aureus strains isolated from air, patient, food and animal. Our results show that S. aureus isolated from patients and air are the most sensitive to UV-C rays and that their inactivation achieves a greater than 2-log reduction after a UV-C exposure of 210 mJ cm−2. However, the strain isolated from food is the most resistant one. The fatty acid analysis indicates that this strain (food) reveals a decrease of branched chain fatty acids (BCFA iso and anteiso) and an increase of straight chain saturated fatty acids (SCFA).

This paper aimed to the study of microbiological quality of wastewater effluents issued from a sand filter system used as a secondary treatment; this sand filter was coupled to UV irradiation system as a tertiary treatment to assume their possible application as alternatives to chemical disinfection of municipal wastewater before agronomic utilization. For that reason, an infiltration basin of 100 m² of area equipped with two wells of sampling, in the center and in the periphery, has been constructed on the irrigated perimeter of Dissa in Gabes (south east of Tunisia). A comparative study was undertaken concerning the quality of effluents obtained from the sand filter as secondary effluent and from the UV irradiation disinfection system as a tertiary municipal wastewater treatment. Both the combined systems gave effluent of excellent microbiological quality (almost total absence of E. coli, faecal coliforms and P. aeruginosa). However, if the microbiological quality of effluent remained constant in the case of a sand filter system which depends only on the quality of the influent, while with the UV-disinfection process, microbiological quality of tertiary effluent was shown to depend on the quality of secondary effluent. The monitoring of the UV irradiation device using a UV dose of around 96 mW.s.cm-2 and corresponding to an exposure time of 16 sec, for the secondary effluent at the outlet of Sand Filter, showed that the average bacterial inactivation rate was around 3 U-Log for E. coli, faecal coliforms and P. aeruginosa, respectively. Therefore, the average concentration remaining in the effluent at the output of the UV reactor, was less than a 100 cfu/ 100 ml for E. coli and faecal coliforms, and less than a 100 bacteria/ 100 ml for P. aeruginosa. These values coincided with the range recommended by several standardized international guidelines.

This paper deals with the study of bacteriological quality of effluents that have undergone consecutively different macrofiltration system (pressure sand filter or disc filter used as a secondary treatment) and UV254 irradiation process (used as a tertiary treatment). These two successive systems of treatment were evaluated to determine their possible application as commonly alternatives to the conventional system of wastewater treatment and disinfection before wastewater reuse. They both combined systems of wastewater treatment released effluent of excellent bacteriological quality, with almost total absence of feacal coliforms, of E. coli and of P. aeruginosa). However, if the bacteriological quality of the effluent remained constant in the case of macrofiltration system (disc filter or pressure sand filter); the UV disinfection process showed to deeply depend on the quality of effluent, particularly with regard to UV transmittance. The daily bacteriological monitoring of the secondary effluent at the exit of the pressure sand filter by UV reactor and by using a dose of 96 mJ/cm(2), corresponding to an exposure of 16 min, showed an average rate of inactivation of around 3 U-Log, for feacal coliforms, E. coli and P. aeruginosa, respectively. Therefore, the average bacterial concentration remaining in the water at the exit of the UV reactor is less than 1000 cfu/100 ml for feacal coliform and E. coli. For P. aeruginosa, the remaining number is less than 100 bacteria/100 ml. These two last values coincide substantially with the range recommended by several standardized international guidelines. Therefore, numerous authors reported that P. aeruginosa is very resistant to UV irradiation compared to the other bacterial indicators. In contrast, our study revealed that feacal coliforms and E. coli were more UV light resistant than P. aeruginosa. This finding could be explained by the fact that E. coli and feacal coliform forms aggregates in the treated effluent, while P. aeruginosa exists either as discrete cells or as cell pairs.

In recent years, soil contamination with pesticides has become a crucial news issue with serious short- and long-term effects on human health and its environment. Pesticides play a significant role in the success of modern farming and food production. These compounds have potential for toxicity and adverse effects on human health and ecological soil systems. Pentachlorophenol (PCP) is one of the most recalcitrant chemicals polluting the environment for its stable aromatic ring system and chloride content. Nowadays, many sites are contaminated with this substance. In these areas, concentrations may stay high for a long time because of slow degradation in the soil due to the negative effects that PCP has on soil microbial populations. Bioremediation of PCP contaminated sites can be realized introducing directly, into a contaminated system, microorganisms able to consume selectively the target compound (bioaugmentation) or increasing the microbial indigenous population by addiction of nutrients in form of organic and/or inorganic fertilizers and biosolids (biostimulation). In the present chapter, we present an overview of the effect of PCP pesticide contamination on soil microbial populations (density and diversity), enzymatic activity and physicochemical parameters. Additionally, the bioremediation process will be detailed.

Pentachlorophenol (PCP) is quite persistent in the environment and severely affects different ecosystems including forest soil. The main objective of this work was to study different bioremediation processes of artificially PCP (100 mg kg-1) contaminated forest soil (Sc). In fact, we used bioaugmentation by adding two different bacterial consortia B1 and B2, biostimulation procedures by amendments based on forest compost (FC), municipal solid waste compost (MC), sewage sludge (SS), and phosphate, and their combined treatments. Soil physical and chemical properties, residual PCP, soil microbial biomass carbon, soil respiration and some enzymatic activities at zero time and after 30 d of incubation, were evaluated. A net reduction of PCP, 71% of the initial concentration, after 30 d-incubation occurred in the sample Sc+B1+FC, as the best performance among all treatments, due to natural attenuation, immobilization of PCP molecules in the forest soil through organic amendments, and the action of the exogenous microbial consortium B1. The single application of FC or B1 led to a depletion of PCP concentration of 52% and 41%, respectively. Soil microbial biomass carbon decreased in PCP contaminated soil but it increased when organic amendment also in combination with microbial consortia was carried out as bioremediation action. Soil respiration underwent no changes in contaminated soil and increased under FC based bioremediation treatment. These results demonstrate that the combined treatments of biostimulation and bioaugmentation might be a promising process for remediation of PCP contaminated soil.

The valorization of different organic residues like municipal solid wastes, sewage sludge and olive mill wastewater is becoming more and more worrying in the different modern communities and is becoming relevant and crucial in terms of environmental preservation. The choice of the treatment technique should not be only from the point of view of economic profitability but, above all, must consider the efficiency of the treatment method. Thus, an attempt to remove polyphenols from olive mill wastewater would have a double interest: on the one hand, to solve a major environmental problem and to recover and valorize the olive mill wastewater for advanced applications in food processing and soil amendments. It is also interesting to think of associating two harmful wastes by co-composting such as sewage sludge-vegetable gardens, sewage sludge-municipal solid waste, and green wastes-olive mill wastewater…, to get a mixed compost of good physical–chemical and biological qualities useful for agricultural soil fertilization. Finally, in order to be more practical, we will describe specifically in this chapter a new variant of composting and co-composting technology intended for waste treatment that is very simple, inexpensive and easy to implement.

In December 2019, there was a cluster of pneumonia cases in Wuhan, a city of about 11 million people in Hubei Province. The World Health Organization (WHO), qualified CoVid-19 as an emerging infectious disease on March 11, 2020, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) which spreads around the world. Coronaviruses are also included in the list of viruses likely to be found in raw sewage, as are other viruses belonging to the Picornaviridae family. SRAS-CoV-2 has been detected in wastewater worldwide such as the USA, France, Netherlands, Australia, and Italy according to the National Research Institute for Public Health and the Environment. In addition, the SARS-CoV-2 could infect many animals since it has been noticed in pigs, domestic and wild birds, bats, rodents, dogs, cats, tigers, cattle. Therefore, the SARS-CoV-2 molecular characterization in the environment, particularly in wastewater and animals, appeared to be a novel approach to monitor the outbreaks of viral pandemics. This review will be focused on the description of some virological characteristics of these emerging viruses, the different human and zoonotic coronaviruses, the sources of contamination of wastewater by coronaviruses and their potential procedures of disinfection from wastewater.