Preparation and characterization of activated carbon from sunflower seed oil residue via microwave assisted K2CO3 activation

Sunflower seed oil residue, a by-product of sunflower seed oil refining, was utilized as a feedstock for preparation of activated carbon (SSHAC) via microwave induced K(2)CO(3) chemical activation. SSHAC was characterized by Fourier transform infrared spectroscopy, nitrogen adsorption-desorption and elemental analysis. Surface acidity/basicity was examined with acid-base titration, while the adsorptive properties of SSHAC were quantified using methylene blue (MB) and acid blue 15 (AB). The monolayer adsorption capacities of MB and AB were 473.44 and 430.37 mg/g, while the Brunauer-Emmett-Teller surface area, Langmuir surface area and total pore volume were 1411.55 m(2)/g, 2137.72 m(2)/g and 0.836 cm(3)/g, respectively. The findings revealed the potential to prepare high surface area activated carbon from sunflower seed oil residue by microwave irradiation.     

Effects of glucose and phenol on soluble microbial products (SMP) in sequencing batch reactor systems

Soluble microbial products (SMP) are ubiquitously present in the effluents of biological wastewater treatment systems. In sequencing batch reactor (SBR) systems, effects of influent concentration and temperature on the amount and the molecular weight (MW) distribution of SMP were investigated for the two substrates, glucose and phenol. The values of effluent SMP/S₀ of phenol were higher than those of glucose at different influent concentrations and temperatures. It was found that the effluent SMP (S_e) was linearly correlated to the influent total organic carbon (TOC) (S₀) for both substrates. The slope and intercept of the equation were affected by the temperature. According to the analysis of the MW distribution, it was shown that there exists a bimodal pattern with the majority of SMP having a MW<1 kDa or >10 kDa. The low MW fraction (<1 kDa) amounts to 47.3–70.4% of the effluent SMP. The high MW fraction (>10 kDa) slightly fluctuates in the range of 21.2–32.8% of the effluent SMP.     

Phenol-mediated improved performance of active biomass for treatment of distillery wastewater

Activated sludge from a wastewater treatment plant consists of a consortium of microbes that utilize various organic molecules including persistent organic pollutants for their survival. Phenolic compounds and their derivatives along with dibenzofuran (DBF) are found as dominating pollutants in distillery waste. The acclimatization process leads to selective enrichment of the microbial community; and in this study, we report the acclimatizing effect of phenol on improving the treatment efficiency of two different distillery sludges—sludge from conventional aeration tanks (CAT), and from an extended aeration tank (EAT). The adaptation-dependent performance of activated biomass was studied by monitoring the increase in colony-forming units (CFUs) on mineral media and the utilization pattern for phenol (300×10³ and 530×10³ CFU for CAT and EAT sludge, respectively) and DBF (260×10³ and 430×10³ CFU for CAT and EAT sludge, respectively). The study showed that the acclimatization process remarkably improved the performance sludge for treatment of distillery wastewater. There was an improvement in chemical oxygen demand (COD) removal efficiency from 19% (unacclimatized sludge) to 31% in the case of acclimatized sludge (raw wastewater), which improved further to 82% and 87% with dilution of wastewater by 10 times (0.1×) and by 50 times (0.02×), respectively. Highest growth yields were observed with 0.1× wastewater (0.324 and 0.308 g g⁻¹ d⁻¹ for CAT and EAT sludges, respectively), while lower values are reported for the remaining two forms of wastewater. The study proposes that acclimatization step could be included as part of a treatment plant where the activated biomass could be intermittently metabolically charged by exposing it to selected molecules to increase treatment efficiency.     

Improvement of nitrogen removal and reduction of operating costs in an activated sludge process with feedforward–cascade control strategy

In this paper, a feedforward–cascade controller for dissolved oxygen concentration in an activated sludge process is designed in order to meet stricter effluent quality standards at a minimum cost. Conventional proportional and integral (PI) constant dissolved oxygen set-point control and feedforward–cascade dissolved oxygen set-point control are evaluated using the reduced model of activated sludge model no. 1 and reduced IWA simulation benchmark. The feedforward–cascade control has been based on a hierarchical structure where a high level or cascade control selects the set-point of the low level or conventional controller and low level directly control dissolved oxygen concentration. And feedforward control is introduced in the control system for preventing the influent loading from influencing the system. Simulation results show that feedforward–cascade control of the activated sludge process is more successful than conventional PI control in meeting the effluent standards and reducing operational costs. This control strategy can be expected to be accepted by the operating personnel in wastewater treatment plants.     

Biodegradation of wastewater pollutants by activated sludge encapsulated inside calcium-alginate beads in a tubular packed bed reactor

The wastewater treatment plants produce large quantities of biomass (sludge) that require about one-third of the total inversion and operation plant costs for their treatment. By the microorganisms immobilization it is possible to handle high cell concentration in the reactor, increasing its efficiency, reducing the loss of biomass and the wash out is avoided. Moreover, there is no cell growth then the sludge production is reduced. In this study, the COD removal and VSS variation were modeled in a tubular reactor with activated sludge immobilized in Ca-alginate. Moreover, two aspects that are commonly not considered in the performance of the actual reactors of this kind were introduced; the performance in non-steady state and the dispersion effect. The model was calibrated with an actual wastewater taken out from a Mexican wastewater treatment plant. The results of the performance of the tubular bioreactor at different scenarios (i.e., different residence time and VSS in the reactor) are presented. With longer residence times and higher VSS concentration in the Ca-alginate beads in the tubular bioreactor it is possible to increase the time operation of the bioreactor and to treat higher volumes of wastewater. During the process, the sludge generation was drastically reduced and it is possible to remove nitrogen form the wastewater making this process more attractive.     

Antibiotic resistance and survival of faecal coliforms in activated sludge system in a semi-arid region (Beni Mellal,Morocco)

The activated sludge process is one of the biological treatment methods used in many countries to reduce the high levels of organic and mineral pollutants and pathogenic micro-organisms present in wastewater. The present work was undertaken to study the dynamic and antibiotic-resistance of faecal coliforms (FC) in the activated sludge system of Beni Mellal. This work has also as objective the study of the survival of FC, protozoan cysts, helminth eggs and FC antibiotic resistance in the sludge dehydrated in drying beds in order to know if the agricultural usage of sludge presents any problems to public health. The activated sludge treatment of Beni Mellal resulted in an average reduction of FC and faecal streptococci of 90.75 and 91.06%, respectively. The overall resistance (resistance to at least one antibiotic) of 111 FC strains isolated from the system was 72.07%. This treatment system did not increase the incidence of FC antibiotic resistance in treated wastewaters. The antibiotic resistance of FC was found to be similar in both raw (71.05%) and treated sewage (77.77%). High levels of antibiotic resistance were towards streptomycin (54.05%), ampicillin (42.34%), amoxicillin (42.34%) and amoxicillin–clavulanic acid (31.53%). The treatment of sludge in drying beds appeared to be efficient in eliminating pathogenic micro-organisms: FC, protozoan cysts and helminth eggs. Moreover, the FC antibiotic resistance did not change over time in sludge-drying bed. According to the standard norms, agricultural utilization of this sludge cannot be excluded. However, it is important to study in the receptor environment the survival and the behaviour of antibiotic-resistant FC present in sludge and water.     

High phylogenetic diversity of transconjugants carrying plasmid pJP4 in an activated sludge-derived microbial community

Transconjugants of plasmid pJP4, originating from an agar plate mating of a Pseudomonas putida donor with an activated sludge-derived microbial community, were isolated and identified by partial 16S rDNA sequencing. The transconjugant strains belonged to a variety of genera of the alpha-, beta-, gamabeta- and gamma-classes of the Proteobacteria, mostly to the families Rhizobiaceae and Comamonadaceae and the genus Stenotrophomonas. Only P. putida and Delftia spp. strains were able to grow on 2,4-D as the sole carbon source.     

Influence of operation conditions and additives on the development of producer gas and tar reduction in air gasification of construction woody wastes using a two-stage gasifier

Air gasification was conducted with fractions of construction woody wastes in a two-stage gasifier, consisting of a fluidized bed zone and a tar cracking zone. The aim of this work is to investigate the influence of reaction conditions and additives on the composition of producer gas and tar content in producer gas.A producer gas obtained with activated carbon of 540 g at an ER of 0.26 was mainly composed of H₂ (25 vol.%), CO (22 vol.%) and CH₄ (5 vol.%). Regarding tar removal efficiency, activated carbon was better than olivine. The tar removal rate with virgin activated carbon reached up to 80%. The reuse of spent activated carbon caused an efficiency loss in tar removal to some extent. Overall, it seems that the strong need for intensive downstream tar removal measurements can be removed with the use of a two-stage gasifier and the application of activated carbon.     

Adsorption of Phenolic Compounds and Methylene Blue onto Activated Carbon Prepared from Date Fruit Pits

Activated carbon has been prepared from date fruit pits. The carbon, prepared at different burn‐off rates, showed a high uptake of methylene blue. At 92 % burn‐off (weight loss percent of the carbonized pits upon activation), methylene blue uptake was 590 mg/g. With this high capacity, the carbon was then used to study the adsorption of phenol, 2‐nitrophenol, 2,4‐dinitrophenol, and 2,4,6‐trinitrophenol. The prepared activated carbon showed an adsorption capacity better than that of many activated carbons in current use. The experimental adsorption data for the single components were regressed using both Langmuir and Freundlich isotherm models and the fit was generally satisfactory. The experimental adsorption data of the binary system phenol‐2‐nitrophenol were compared with the predicted results using two predictive models: the generalized Langmuir and the IAS models. The data were better represented by the IAS theory than the generalized Langmuir model even though the fit of the experimental data was not adequate.     

Comparative assessment of growth and biodegradation potential of soil isolate in the presence of pesticides

In Pakistan, to increase agricultural production, higher amounts of fertilizers and pesticides are being used. The residues of the applied pesticides stay in the environment and therefore causing contamination of air, water and land. Moreover, agricultural industries are also contributing relatively high quantities of toxic pesticides into the environment. Since most of them have no treatment facilities. These pesticides may be toxic, mutagenic or carcinogenic. They may be bioaccumulated or biomagnified by the biota. Therefore its removal from environmental systems needs special attention. In this study, bacterial isolate, Pseudomonas, designated as IES-Ps-1, was used to assess its potential for pesticide removal from industrial wastewater using the biosimulator (activated sludge process). During experimental studies conducted in the flask as well as in biosimulator, it was observed that IES-Ps-1 grows normally at low concentrations of added insecticides when compared with the control test (without pesticide). However, at high concentrations the microbial count decreased but no death occurred and the culture remained in lag phase. In many cases, the growth of organisms in the presence of the particular substrate serves as an indication about its metabolic potential. However, to confirm these results, chemical oxygen demand (COD) and HPLC analysis were performed. Under aerobic culture conditions using mechanical aerators in biosimulator, almost complete removal of Cypermethrin at 20 mg/L dose occurred during 48 h. The study findings indicate that IES-Ps-1 strain, can be used for the treatment of the pesticide contaminated environment. Such study may be valuable to scientist and engineers, who are trying to develop methods for the treatment of toxic organic waste using the biological treatment process.