Model-based Optimization of Biopolymer Production from Glycerol

The present study focuses on sustainable production of biodegradable polymers by Cupriavidus necator DSMZ 545 using glycerol as substrate. The batch growth and biopolymer production kinetics were established in a 7-L bioreactor, which resulted in a total biomass of 8.88 g L–1 and poly(3-hydroxybutyrate) (PHB) accumulation of 6.76 g L–1. The batch kinetic and independently acquired substrate inhibition data were then used to develop a mathematical model for PHB production process. This was eventually used to design different nutrient feeding strategies under constant feed rate, decreasing feed rate, and pseudo steady state of substrate (glycerol) to optimize the PHB production during fed-batch cultivation. Among all the fed-batch cultivation strategies, the highest PHB accumulation and productivity of 13.12 g L–1 and 0.27 g L–1 h–1, respectively, was achieved in fed-batch bioreactor cultivation where a pseudo steady state with respect to glycerol was maintained. This work is licensed under a Creative Commons Attribution 4.0 International License

Development and optimization of low power non-thermal plasma jet operational parameters for treating dyes and emerging contaminants

Emerging contaminants (ECs) have come out as the latest class of environmental contaminants, which are highly recalcitrant and toxic in nature. Currently, no suitable rectification methods are available against the ECs, resulting in a continuous increase in their concentration. Non-thermal plasma, as an advanced oxidation process, has been emerging as a promising technology against the ECs treatment. In the present work, a detailed experimental study is carried out to evaluate the efficacy of a non-thermal plasma jet with two dyes, Rhodamine B and Methylene Blue, as model contaminants. The plasma jet provided a complete dye decoloration in 30 min with an applied voltage of 6.5 kV. .OH, having the highest oxidation potential, acts as the main reactive species, which with direct action on contaminants also acts indirectly by getting converted into H2O2 and O3. Further, the effect of critical operational parameters viz., sample pH, applied voltage (4.5-6.5 kV), conductivity (5-20 mScm-1), and sample distance on plasma treatment efficacy was also examined. Out of all the assessed parameters, the applied voltage and sample conductivity was found to be the most significant operating parameter. A high voltage and low conductivity were found to favor the dye decoloration, while the pH effect was not that significant. To understand the influence of plasma discharge gas on treatment efficacy, all the experiments are conducted with Argon and Helium gases under the fixed geometrical configuration. Both the gases provided a similar dye decoloration efficiency. The DBD plasma system with complete dye removal also rendered maximum mineralization of 73 % for Rd. B, and 60 % for Met. Blue. Finally, the system's efficiency against the actual ECs (four pharmaceutical compounds, viz., metformin, atenolol, acetaminophen, and ranitidine) and microbial contaminant (Escherichia coli) was also tested.Comment: 23 pages, 7 figure

Increased waterborne blaNDM-1 resistance gene abundances associated with seasonal human pilgrimages to the Upper Ganges River

Antibiotic resistance (AR) is often rooted in inappropriate antibiotic use, but poor water quality and inadequate sanitation exacerbate the problem, especially in emerging countries. An example is increasing multi-AR due to mobile carbapenemases, such as NDM-1 protein (coded by blaNDM-1 genes), which can produce extreme drug-resistant phenotypes. In 2010, NDM-1 positive isolates and blaNDM-1 genes were detected in surface waters across Delhi and have since been detected across the urban world. However, little is known about blaNDM-1 levels in more pristine locations, such as the headwaters of the Upper Ganges River. This area is of particular interest because it receives massive numbers of visitors during seasonal pilgrimages in May/June, including visitors from urban India. Here we quantified blaNDM-1 abundances, other AR genes (ARG) and coliform bacteria in sediments and water column samples from seven sites in the Rishikesh-Haridwar region of the Upper Ganges and five sites on the Yamuna River in Delhi to contrast blaNDM-1 levels and water quality conditions between season and region. Water quality in the Yamuna was very poor (e.g., anoxia at all sites), and blaNDM-1 abundances were high across sites in water (5.4 ± 0.4 log(blaNDM-1·mL-1); 95% confidence interval) and sediment (6.3 ± 0.7 log(blaNDM-1·mg-1)) samples from both seasons. In contrast, water column blaNDM-1 abundances were very low across all sites (2.1 ± 0.6 log(blaNDM-1·mL-1)) in February in the Upper Ganges and water quality was good (e.g., near saturation oxygen). However, per capita blaNDM-1 levels were 20 times greater in June in the Ganges water column relative to February and blaNDM-1 levels significantly correlated with fecal coliform levels (r=0.61; p=0.007). Given waste management infrastructure is limited in Rishikesh-Haridwar; data imply blaNDM-1 levels are higher in visitor's wastes than local residents, which results in seasonally higher blaNDM-1 levels in the river. Pilgrimage areas without adequate waste treatment are possible "hot spots" for AR transmission, and waste treatment must be improved to reduce broader AR dissemination via exposed returning visitors

Bio-physico-chemical treatment for removal of colour from pulp and paper mill effluents

61-64Combination of biological and physico-chemical treatment method is adopted for colour removal of paper mill effluents. On treatment of effluent with Trichoderma sp in batch studies, 72 % colour reduction was achieved within 24 h. In continuous mode, treating effluent with the same fungus in a fluidized bed reactor, around 27 % colour reduction was achieved. This biologically treated effluent is further treated with a poly-electrolyte (potash alum) to improve the colour reduction. Maximum colour reduction of 81 % was obtained by this combined treatment

An energy-efficient process for treatment of sewage sludge

Abstract: A new process technology has been evolved, based on laboratory-scale experimental studies, which addresses the problems of (i) volatile solids reduction (ii) pathogen elimination and (iii) heavy metal removal from sewage sludges with high level of energy and cost conservation. The new process envisages a two-stage, aerobic, biological process. In the first stage, which operates in the batch mode, aerobic sludge digestion takes place at a temperature of 55 -60 o C. The aerobically digesting sludge temperature is maintained at this value through the heat released by the process itself. Experimental results show that this is possible by maintaining the initial concentration of biodegradable solids in the sludge at a value not less than 20 g/l. Elemental sulfur is added to the system at the start of the batch operation. The batch time is about 24 hours, during the initial 4-5 hours of which the sludge undergoes aerobic digestion at a temperature of 55 -60 o C under auto-heated conditions. This was experimentally observed to be sufficient enough to eliminate all indicator organisms. The temperature starts falling with reduction in the solids concentration and this is accompanied by reduction in the sludge pH due to the activity of the autotrophic, thermophilic thiobacillus sp. present in the sludge. At the end of the batch operation, the pH comes down to 4.5 -5.0 and the temperature, 45 o C. This is then subjected to further treatment in a continuous process where the pH is maintained at 2.0 and temperature at 45 o C. The output from this second stage is a stabilized sludge with complete removal of indicator bacteria and more than 98% of the heavy metals originally present in the sludge leached out. A crucial point in the entire process is the development of a consortium of aerobic sulphur oxidizing microorganisms native to municipal sewage sludge that is capable of reducing the pH of municipal sewage sludge from 7.0 to 4.8 at 60°C and from 4.8 to 2.0 under mildly-thermophilic (45°C) temperatures. Keywords: Aerobic sludge digestion, heavy metal leaching, indicator organism, thermophilic, thiobacilli,. INTRODUCTION Aerobic digestion of biological sludges could be done under mesophilic conditions (25 -40C) as well as under thermophilic conditions (45-75C). Thermophilic digestion is attractive due to its high rate of solids removal. Also, under thermophilic conditions, pathogenic organisms are inactivated very effectively in a way that stabilized sludge will be a processed and sterilized end product, safe for land disposal (Kabrik and Jewell 1982). However, heat is required for keeping thermophilic digesters at the desired operational temperature range (normally at 55-65ºC). A very attractive approach to solve this high energy input requirement problem is the auto-heated thermophilic process in which the digestion process can generate the energy required to keep itself under the thermophilic temperature range. For an aerobic digestion process, autothermal conditions could be achieved through the heat generated by the bio-oxidation energy released during the digestion process (Kambhu and Andrews 1969). The amount of energy released through aerobic digestion is inherent and same to both mesophilic and thermophilic digestions. However, the increased rate of degradation under thermophilic conditions may enhance the feasibility of operating the process as an autothermal thermophilic aerobic digestion (ATAD) process. This could happen when the heat released by the biological oxidation process overcomes all the heat losses taking place from the digeste

Recombinant Microbial Bioremediation for the Treatment of Heavy Metals

Heavy metals related contamination constitutes an important health concern throughout the world. Since many polluted soils and wastes contain heavy metals in various concentrations, chemical and biological examination of heavy metals is required while working with problems of environmental concern. Use of highly precise and sensitive methods is, therefore, an urgent requirement for both the detection and quantification of these toxic and hazardous compounds. Recently, environmentalists have shown a lot of interest in the use of recombinant microbial technology for treatment of heavy metals from industrial wastewater. In the present work, the authors have discussed the application of genetic engineering for bioremediation of heavy metals as well as the development of microbial biosensors for detection and quantification of heavy metals at contaminated sites. The use of genetically engineered whole-cells containing reporter genes coupled to biological recognition components allows for the design of rapid, highly specific, and sensitive biosensing system

The remediation of wastewater containing 4-chlorophenol using integrated photocatalytic and biological treatment

Goel, Mukesh Chovelon, Jean-Marc Ferronato, Corinne Bayard, Remy Sreekrishnan, T. R.In this work. the performance of integrated photocatalytic and biological treatment was studied for the degradation of 4-chlorophenol (MCP) present in wastewaters. Photocatalysis was used as a pre-treatment to biological degradation Pollutant removal efficiency was quantified using MCP removal and total organic carbon (TOC) removal Both photocatalytic as well as biological treatments were carried out in batch reactors, using TiO2 as the photocatalyst. The inoculum for biological experiments was obtained from paper mill effluent treatment plant and was developed through a process of selection and acclimatization. Effect of TiO2 concentration on the photocatalytic degradation of MCP was studied along with the effect of the duration of photochemical oxidation and glucose concentrations (0 g/L, 1 g/L and 2 g/L) on the biodegradation of MCP Integrated biological and photochemical degradation was found to be more effective in treating MCP, especially at higher concentrations (400 mg/L) An initial MCP concentration of 400 mg/L required 96 h for complete mineralization when treated with the process combination, whereas the treatment went on up to 264 h when biodegradation alone was employed (C) 2009 Elsevier B.V All rights reserved

Identification and assessment of appropriate remediation management techniques for the recovery of soil-like material produced in landfill mining

Landfill mining has received major attention in recent years for the reclamation of waste disposal sites, including in developing countries such as India where significant efforts are being made to manage sites in this way. The bulk of the material obtained from landfill mining consists of fine-grained soil-like material (SLM) but its direct reuse in off-site applications is restricted due to the presence of harmful heavy metals, soluble salts and other pollutants. In this study, appropriate techniques for managing SLM to permit recovery and reuse are assessed. As a result, experimental investigation explores the efficacy of two remediation techniques considered appropriate for SLM management: electrokinetic remediation and phytoremediation. These were applied to SLM from a recently mined landfill and their ability to reduce heavy metal and other soluble salt burdens assessed. Electrokinetic remediation has shown considerable potential to mobilise and transport heavy metals and soluble salts through and from the SLM over an eight-week period. Phytoremediation experiments also demonstrated mobilisation and uptake of metals from the SLM over a similar duration although relatively low amounts were recovered as a result of the low biomass produced over this period. Both technologies have demonstrated potential for recovery of metals from SLM, as well as recovering the SLM itself as a potential resource