Effectiveness of combined tools: adsorption, bioaugmentation and phytoremediation for pesticides removal from wastewater.

The aim of this study was the comparison of two process in pentachlorophenol (PCP: 100 mg L-1) removal by combined process bioaugmentation-adsorption and bioaugmentation-phytoremediation in secondary treated wastewater (STWW). The phytoremediation procedure was conducted by using two plants such as Typha angustifolia and Schoenoplectus acutus, and the bioaugmentation procedure was operated by Pseudomonas putida HM 627618 as a plant growth promoting bacteria (PGPR). The adsorption process was performed by palm date activated carbon. The PCP monitoring was assessed by high performance liquid chromatography (HPLC) and the optical density determination at 600 nm (OD600). The performance of the two processes was observed by the determination of total bacteria, chlorophylls and physical and chemical analysis (COD, pH, conductivity, chloride, and organic carbon). The alfalfa seed germination test was conducted to assess the two operational performance procedures. According to the results obtained from the physical and chemical analysis of the treated STWW, there was no significant differences in the pH and in the EC content of the bioaugmentation-phytoremediation treatment, while a significant increase of the EC content was observed in the bioaugmentation-adsorption to 5.08 mS cm-1. The COD value significantly decreased up to 1320 mg L-1 in bioaugmentation-adsorption treatment (control value 2400 mg L-1) and 98 mg L-1 in bioaugmentation-phytoremediation treatment (control value 98 mg L-1). Microbial biomass monitoring of P. putida shows significant greater in both processes in the order of 9.18 and 7.01 Log CFU mL-1 for bioaugmentation-adsorption and bioaugmentation-phytoremediation, respectively. The chlorophyll content in Typha angustifolia and Schoenoplectus acutus significantly decreased after 144 h with the exception of the chlorophyll a content of Schoenoplectus acutus in which the content increased up to 3.31 mg mL-1. Comparing the performance of these two treatments, it was found according to HPLC analysis that the bioaugmentation-adsorption process was more efficient in removing about 97% of PCP after 48 h, against around 90% of PCP after 72 h for the phytoremediation-bioaugmentation. The alfalfa seeds showed a germination rate after the 5th day of incubation of 100% and 95%, respectively for the PCP-non-contaminated and treated STWW, while for wastewater containing PCP the germination was totally inhibited.

This paper describing sensitive methods of combined bioaugmentation-phytoremediation and bioaugmentation-adsorption for pentachlorophenol (PCP) depletion in wastewater. The novelty is the choice of a macrophyte Typha angustifolia and Schoenoplectus acutus in constructed wetland fixed in clay matrix. The two-selected plants are still used for the elimination of heavy metals but not for pesticide in wastewater. Also, the combined process bioaugmentation-adsorption was not tested in other researches. On the other side, in this study, the phytoremediation technique combined with bacteria positively affected the plants activity in order to promote pollutant remediation. Hence, the Pseudomonas putida HM 627618 in wastewater with the macrophyte presence or date stone adsorbent have a great capacity to reduce this pollutant (PCP) by improving the bioremediation process.

Effects of heavy metals on growth and biofilm-producing abilities of Salmonella enterica isolated from Tunisia.

This study aims to test the toxicity of some metallic elements on Salmonella enterica strains and their power to grow and to develop a biofilm to overcome this environmental stress. From 50 selected strains of Salmonella, 70% belong to the Kentucky serotypes that is the most frequent one, followed by the other serotypes such as Amsterdam 6%, anatum 4%, derby 4% Enteritidis 4%, Zanzibar 4%, typhyrimium 2%, gallinaruim 2%, inbondaka 2% and Newport 2%. All the strains have presented the invA invasion gene involved in the virulence and Salmonella infection. Genotypic BOX-PCR analysis of these strains showed 18 profiles, with a discrimination index of 0.93. The Salmonella growth has mainly revealed that the variation of the rates of different metallic elements showed a significant influence on the Salmonella growth. The qualitative, quantitative study and biofilm tubes showed that 40% of the strains have a strong capacity to form biofilm, and the wild-type phenotypes (RDAR; rigid film; Strong), This phenotype varies according to the nature and the concentration of the metal (0.1 mM-1 mM) considered. In the presence of copper, zinc, cobalt, and chromium, the Salmonella strains showed a potent capacity to form a biofilm with a slight variation in the wild-type phenotype. However, when chromium rates increased, Salmonella loses the RDAR morphotype. Addition of mercury and cadmium in the growth medium reduced the production of Salmonella biofilm by around 14 and 15%, respectively, if compared with the control free of metals.

Combined bioaugmentation and biostimulation techniques in bioremediation of pentachlorophenol contaminated forest soil.

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.

Removal of pentachlorophenol from contaminated wastewater using phytoremediation and bioaugmentation processes.

The phytoremediation procedure was conducted by Lemna gibba (L) and Typha angustifolia (T) and the bioaugmentation procedure used P. putida HM627618. The ability of the selected P. putida HM627618 to tolerate and remove PCP (200 mg L-1) was measured by high performance liquid chromatography analysis and optical density at 600 nm. Five different experiments were conducted in secondary treated wastewater for PCP testing removal (100 mg L-1) including two phytoremediation assays (T + PCP; L + PCP), three bioaugmentation-phytoremediation assays (T + B + PCP; L + B + PCP; L + T + B + PCP) and a negative control assay with PCP. Various analytical parameters were determined in this study such as bacterial count, chlorophylls a and b, COD, pH and PCP content. The main results showed that the average PCP removal by P. putida HM627618 was around 87.5% after 7 days of incubation, and 88% of PCP removal was achieved by treatment (T + B) after 9 days. During these experiments, pH, COD and chloride content showed a net increase in all treatments. The chlorophylls a and b in case of (T) and (L) Chlorophylls a and b for T and L phytoremediation showed a decrease with a value less than 10 µg/mg of fresh material after 20 days of cultivation.