Effect of Biofilm in Waste Water Treatment by Using Bactericidal Activity of Nitrogen Doped Metal Oxide Nanoparticles

Background: Biofilm of different microorganisms can stabilize harmful components from waste water. It can be effectively use for the treatment of waste water. Objective: Development of Rotating Drum Biological Reactor (RDBR) for the treatment of waste water and to study the effect of biofilm developed on RBDR for the reduction in BOD, COD and phenol concentration in waste water. Synthesis of TiO2 nanoparticles to study antimicrobial property against developed biofilm. Results: Synthetic waste water with initial concentration of phenol as 50 mg/lit and with COD and BOD values 2080 mg/lit and 1600 mg/lit respectively was treated in RDBR. After 60 hrs of operation phenol concentration drops to 0.0028 mg/lit and COD, BOD values were reduced to 178 mg/lit and 71.2 mg/lit respectively. The reduction of phenol concentration was upto 99.7%. Conclusion: Based on the experimental results we can conclude that rotating drum biological reactor (RDBR) technology is one of the promising technology for the treatment of waste water. After treatment of synthetic waste water in RDBR there was drastic reduction in the initial concentrations of COD, BOD and Phenol was observed. Results show the reduction in phenol concentration upto 99.7%. It has been also found that nitrogen doped TiO2 nanoparticles shows good antimicrobial activity over the biofilm developed. INTRODUCTION Water is the most important constituent for all the living things. Water contamination is now a major problem in the global context as a consequence of industrialization, globalization, population growth, urbanization and warfare combined with increased wealth and more extravagant lifestyles (UNWorld Water Development Report, 2006). Eutrophication of lakes and the sea is caused by discharge of nutrients originating from of human activities, industries and agriculture, which threatens the maintenance of biodiversity and human health. Suspended, colloidal or dissolved degradable organic materials, quantities and ratios depend on the nature of the wastewater characteristics of wastewater are measured in terms of chemical oxygen demand (COD), Biological oxygen demand (BOD), and volatile suspended solid (VSS). Biological wastewater treatment is therefore of utmost importance for the wellbeing of our water bodies. Biological treatment is one of the most widely used removal methods as well as for partial or complete stabilization of biologically degradable substances in wastewater and wastes. Most biological waste and wastewater treatment processes employ bacteria as primary microorganisms; certain other micro-organisms may play an important role. Degradation of organic matter is effected by its use as food by micro-organisms to produce protoplasm for new cells during the growth process, population dynamics of bacteria is biological treatment depends on environmental factors which include pH, temperature, type and concentration of essential nutrients (e.g. Nitrogen, Phosphorous, Sulphur etc.), essential minerals, osmotic pressure, media toxicity, by-products and degree of mixing.A biofilm can be defined as a complex coherent structure of cells and cellular products, like extra-cellular polymers (Characklis, 1990), which either form spontaneously as large, dense granules (Lettinga et al., 1980), or grow attached on a static solid surface (static biofilms) or on suspended carriers (particle supported biofilms) (Heijnen, 1984). Biological wastewater treatment is mainly carried out by prokaryotes, even if fungi, protozoa, algae and rotifers may also be represented (Bitton G, 2005). Municipal wastewater is composed of organic material, i.e. proteins, carbohydrates, fats and oils; nutrients, mainly nitrogen and phosphorus; as well as trace amounts of recalcitrant organic compounds and Metals (Bitton G, 2005). The most frequently found prokaryotes in biological wastewater treatment systems belong to the classes Alpha-, Betaand Gamma proteobacteria, Bacteroidetes and Actinobacteria (Wagner M and Loy A, 2002). These bacteria in aquatic environments are predominantly not in a free-floating planktonic stage, but have a tendency to attach to surfaces and form multi-species communities called biofilms (Metcalf & Eddy, PRATIBHA: INTERNATIONAL JOURNAL OF SCIENCE, SPIRITUALITY, BUSINESS AND TECHNOLOGY (IJSSBT), Vol. 2, No. 2, May 2014 ISSN (Print) 2277—7261 19 1991; Syron & Casy, 2007). The microbes produce extracellular polymeric substances (EPS), which form complexes with the surface materials (Andersson S et al., 2009). A mature biofilm is a complex mixture of active and dormant or drying cells, inorganic and organic materials and tunnels filled with water, and the biofilm contains both aerobic and anaerobic niches (Korber et al., 1995; O‘Toole et al., 2000). The most commonly used process for the treatment of municipal and industrial waste water is activated sludge process, but increasingly biofilm technologies are utilized. Biofilm waste water treatment processes can be roughly divided into 1) the fixed-medium systems, and 2) moving-medium systems (Rodgers et al., 2003). In the fixed-medium systems (fixed bed bioreactor; FBBR) the biological reactions take place in the biofilm growing on a static medium. In the moving medium systems the biofilm media are kept in continuous movement by mechanical, hydraulic or air forces. Rotating bed bioreactors (RBBR) are an application of moving bed biofilm reactors with a higher filling rate of carrier elements. Nanoparticles in waste water treatment: The waste water treatment plant in which trickling filter, RBC, packed bed reactor are used involve formation of biofilm, which reduces the COD of treated water (Nicholas P. Cheremisinoff,2003). More recently, several natural and engineered nanomaterials have also been shown to have strong antimicrobial properties, including chitosan (Qi et al., 2004), silver nanoparticles (nAg) (Morones et al., 2005), photocatalytic TiO2 (Cho et al., 2005; Wei et al., 1994), fullerol (Badireddy et al., 2007), aqueous fullerene nanoparticles (nC60) (Lyon et al., 2006), and carbon nanotubes (CNT) (Kang et al., 2007). The biofilm form during water treatment process can be stabilised/ degraded by using the metal oxide nanoparticles such as TiO2, the surface of TiO2 crystal is occupied by O2 atoms with high electron density. The bactericidal effect of TiO2 is attributed to the decomposition of bacterial outer membranes by reactive oxygen species [ROS], primarily hydroxyl radicals [*OH] which leads to phospholipids peroxidation and ultimately cell death. Nitrogen Doping Of Metal Oxide Nanoparticles: TiO2 is the most commonly used semiconductor photocatalyst.Among the different nanomaterials, it is the most studied. Activated by UV-A irradiation, its photocatalytic properties have been utilized in various environmental applications to remove contaminants from both water and air (Gelover et al., 2006; Murray et al., 2007; Salthammer and Fuhrmann, 2007). A wealth of information on TiO2 photocatalytic inactivation of bacteria has been acquired over the last 20 years (Matsunaga et al., 1985; Wei et al., 1994). TiO2 can kill both Gramnegative and Gram-positive bacteria, although Gram-positive bacteria are less sensitive due to their ability to form spores (Wei et al., 1994). More recently, nano-sized TiO2 was also reported to kill viruses including poliovirus 1 (Watts et al., 1995), hepatitis B virus (Zan et al., 2007), Herpes simplex virus (Hajkova et al., 2007), and MS2 bacteriophage (Cho et al., 2005). The concentration of TiO2 usually required to kill bacteria varies between 100 and 1000 ppm, depending on the size of the particles and the intensity and wavelength of the light used (Wei et al., 1994). An attractive feature of TiO2 photocatalytic disinfection is its potential to be activated by visible light, e.g. sunlight. Metal doping has long been known to improve visible light absorbance of TiO2 (Anpo et al., 2001), and increase its photocatalytic activity under UV irradiation (Choi et al., 1994). Materials and Methods