Pritha Chatterjee

Preparation of a fouling-resistant sustainable cathode for a single-chambered microbial fuel cell.

Two different binder materials of varying water affinity, viz. poly vinyl alcohol (PVA) and poly-tetrafluoroethylene (PTFE), and biocide vanillin were tested for cathode fouling in a single chamber air-cathode microbial fuel cell (MFC) constructed with a low-cost baked clayware cylinder and operated under fed-batch mode. PVA and PTFE loadings of 0.5 mg/cm(2) were used for MFC-1 and MFC-2, respectively as a binder; and a 1:1 mixture of PVA + PTFE was used as binder in MFC-3 with same binder loading. Vanillin was mixed with PVA and also applied at a loading of 0.5 mg/cm(2) for MFC-4. Results showed organic matter removal efficiencies around 90% for all MFCs both before and after fouling. Coulombic efficiency was, however, found to decrease 50% after fouling in the MFC-3 coated with both PVA and PTFE. After 5 weeks of operation, due to fouling 56, 40 and 69% reduction in power densities were observed in MFC-1, MFC-2 and MFC-3, respectively. In the MFC-4 having PVA and vanillin, the least fouling was observed. A consistent volumetric power of 233 mW/m(3) was observed for MFC-4, thus potentially offering a suitable solution to alleviate the problem of fouling in the making of single-chamber air-cathode MFCs.

Development of anammox process for removal of nitrogen from wastewater in a novel self-sustainable biofilm reactor.

Effluent of an upflow anaerobic sludge blanket reactor was treated in a downflow rope-bed-biofilm-reactor (RBBR) to remove residual organic matter and nitrogen. Nitrogen removal was observed in phase 1 and phase 2 with and without aeration, respectively for 320days each. Organic matter, ammonia and total nitrogen removal efficiencies of 78±2%, 95±1% and 79±11% were obtained in phase 1 and 78±2%, 93±9% and 87±6% in phase 2, respectively. In phase 2, anammox bacteria had a specific anammox activity of 3.35gNm(-2)day(-1). Heme c concentration, sludge characteristics and reaction ratios of dissolved oxygen, alkalinity and pH corroborated contribution of anammox process. Using experimental results kinetic coefficients required for design of RBBR were estimated. Anammox gave more stable performance under varying nitrogen loading and this option is more sustainable for solving problem of nitrogen removal from sewage.

Low efficiency of sewage treatment plants due to unskilled operations in India

Centralized sewage treatment plants may not be a sustainable solution for a developing country such as India. Therefore, we conducted for the first time an integrated assessment of the different technologies currently used for sewage treatment in the state of West Bengal, India. Five decentralized sewage treatment plants and one centralized sewage treatment plant located in different parts of Kolkata were evaluated. We compared influent and effluent water quality, energy consumed, capital and operating costs, and treated wastewater reuse potential. F test was used to validate results on the effect of working days and holidays and seasons on treated water quality. Wastewater management strategy was assessed by performance indicators. Our results show that treatment efficiency was lowest in anaerobic plants not because of faulty technology but due to unskilled operation. Therefore, performance improvement of plants is expected if factors such as monitoring, training of staff, regular and scrupulous desludging, reuse aspects, and rational water tariff are implemented earnestly.

Increasing methane content in biogas and simultaneous value added product recovery using microbial electrosynthesis

Electrosynthesis of multi-carbon compounds from the carbon dioxide present in biogas is a nascent approach towards purification of biogas. Microbial electrosynthesis (MES) cells, fabricated using different electrode materials, were operated using different electrolytes and mixed anaerobic culture as biocatalysts in the cathodic chamber under an applied cathode potential of -0.7 V vs standard hydrogen electrode (SHE). The rate of production of acetate, isobutyrate, propionate and 2-piperidinone from reduction of CO2 in the cathodic chamber of the MES was 0.81 mM/day, 0.63 mM/day, 0.44 mM/day and 0.53 mM/day, respectively. As methane was also present in the biogas, methyl derivatives of these acids were also found in traces in catholyte. It was observed that the use of nickel foam as an anode, 1 M NiSO4 solution as anolyte, graphite felt as a cathode, phosphate buffer solution as catholyte at a pH of 5.2 proved to be the best possible combination for MES for this study to get enhanced product yield at higher energy efficiency.

Water Pollutants Classification and Its Effects on Environment

With increasing urbanization and advancement of science, researches in nanotechnology and nanomaterial development are experiencing unprecedented expansion. Nanoparticle pollution is considered to be the most difficult pollution being managed and controlled. This chapter briefly describes the different types of water pollutants with a more detailed discussion on nanoparticle pollution. The chapter also gives an effort to visualize the challenges associated with dealing with nanoparticle waste.

New Age of Wastewater Treatment Employing Bio-electrochemical Systems

Bio-electrochemical systems (BESs) as an energy-efficient wastewater treatment technology have attracted increasing interest in the past decade. A BES is a bio-electrochemical reactor capable for conversion of chemical energy present in the chemical bonds of organic compounds directly to other usable forms of chemical energy or electrical energy by using catalytic reactions initiated by micro-organisms in anaerobic conditions. Energy crisis in recent time has attracted researcher’s interest in BESs as an option to produce electric power or other forms of energy from biomass without producing any carbon emission to the environment. BESs can also be utilized at wastewater treatment facilities to treat different types of organic matter present in the wastewater and recover valuable products, thus ensuring economic sustainability. This chapter comprehensively reviews BES with emphasis on their applications for wastewater treatment. It is anticipated that insights offered in this chapter would facilitate for the use of BES as an energy-efficient wastewater treatment option coupled with direct electricity or recovery of resources.

Sludge granulation in an UASB–moving bed biofilm hybrid reactor for efficient organic matter removal and nitrogen removal in biofilm reactor

ABSTRACT A hybrid upflow anaerobic sludge blanket (UASB)–moving bed biofilm (MBB) and rope bed biofilm (RBB) reactor was designed for treatment of sewage. Possibility of enhancing granulation in an UASB reactor using moving media to improve sludge retention was explored while treating low-strength wastewater. The presence of moving media in the top portion of the UASB reactor allowed a high solid retention time even at very short hydraulic retention times and helped in maintaining selection pressure in the sludge bed to promote formation of different sized sludge granules with an average settling velocity of 67 m/h. These granules were also found to contain plenty of extracellular polymeric substance (EPS) such as 58 mg of polysaccharides (PS) per gram of volatile suspended solids (VSS) and protein (PN) content of 37 mg/g VSS. Enriched sludge of nitrogen-removing bacteria forming a porous biofilm on the media in RBB was also observed in a concentration of around 894 g/m2. The nitrogen removing sludge also had a high EPS content of around 22 mg PS/g VSS and 28 mg PN/g VSS. This hybrid UASB-MBB-RBB reactor with enhanced anaerobic granular sludge treating both carbonaceous and nitrogenous matter may be a sustainable solution for decentralized sewage treatment.

Biomass granulation in an upflow anaerobic sludge blanket reactor treating 500 m3/day low strength sewage and post treatment in high rate algal pond

A pilot-scale upflow anaerobic sludge blanket-moving bed biofilm (UASB-MBB) reactor followed by a high-rate algal pond (HRAP) was designed and operated to remove organic matter, nutrients and pathogens from sewage and to facilitate reuse. For an influent chemical oxygen demand (COD) concentration of 233 ± 20 mg/L, final effluent COD was 50 ± 6 mg/L. Successful biomass granulation was observed in the sludge bed of the upflow anaerobic sludge blanket (UASB) reactor after 5 months of operation. Ammonia removal in HRAP was 85.1 ± 2.4% with average influent and effluent ammonia nitrogen concentrations of 20 ± 3 mg/L and 3 ± 1 mg/L, respectively. Phosphate removal after treatment in the HRAP was 91 ± 1%. There was a 2-3 log scale pathogen removal after treatment in HRAP with most probable number (MPN) of the final effluent being 600-800 per 100 mL, which is within acceptable standards for surface irrigation. The blackwater after treatment in UASB-MBBR-HRAP is being reused for gardening and landscaping. This proper hydro-dynamically designed UASB reactor demonstrated successful granulation and moving bed media improved sludge retention in UASB reactor. This combination of UASB-MBB reactor followed by HRAP demonstrated successful sewage treatment for a year covering all seasons.

A Basic Overview of Fuel Cells: Thermodynamics and Cell Efficiency

In the last century, there has been rapid urbanization leading to increased energy demand with an ever increasing load on nonrenewable resources and subsequent escalation of pollution. A viable solution to these two problems can be a power supply technology that is able to produce energy with minimum or zero pollutant emission into the environment. Fuel cells appear to be an eco-friendly power supply technology. Main advantage of fuel cell technology is represented by direct conversion of fuels into electrical energy, with zero emissions, when hydrogen is used as fuel. This article describes the basic overview of fuel cell technology in order to better understand the construction and also the working principle of this eco-friendly technology.