Dynamic Potential of Indigenous and Effective Microbes in Wastewater Treatment Processes

JEYABALAN SANGEETHA,1

SHIVASHARANA CHANDRABANDA THIMMAPPA,2 DEVARAJAN THANGADURAI,3

MEGHA RAMACHANDRA SHINGE,2 ABHISHEK MUNDARAGI,4 RAVICHANDRA HOSPET,3 SIMMI MAXIM STEFFI,1 MOHAMMED ABDUL MUJEEB,2 and PRATHIMA PURUSHOTHAM3

'Department of Environmental Science, Central University of Kerala, Periye, Kasaragod-561716, Kerala, India

2Department of Microbiology and Biotechnology,

Karnatak University, Dharwad-580003, Karnataka, India

'Department of Botany, Karnatak University, Dharwad-580003, Karnataka, India

4Department of Microbiology, Davangere University, Davangere-577002, Karnataka, India

INTRODUCTION

As the world population glows and many developing countries modernize, the significance of water supply and wastewater treatment becomes a much greater area in the welfare of nations. Nowadays, the competition for water sources combines with adverse amalgamates of wastewater releases with freshwater supplies makes subsidiary challenge on wastewater treatment systems (Aziz and Mojiri, 2014). Recently, scientists focus on wastewater treatment by various methods with minimal cost and maximum efficiency. Rapid industrialization and urbanization release large volumes of waste effluents, which are drastically utilized as a potent resource for agriculture and irrigation in urban and rural areas. Wastewater treatment leads significant economic growth, and a healthy environment assists countless livelihoods mainly of fanners and substantially improves the quality of natural water bodies (Marshall et al., 2007; Rajasulochana and Preethy,

2016). It is noted that highly polluted and drastic effects of consumption of such polluted water and its sanitation problem are increasing gradually in most developing countries. This leads to water scarcity and makes a negative influence on human livelihoods, economic development, and environmental sustainability around the world. Hence, there is an urgent need to address the seriousness of the issue to protect water bodies from getting polluted and to develop advanced, cost-effective techniques for the protection and sustainable utilization of natural water resources (Kaur et al., 2012; Shivajirao, 2012; Rajasulochana and Preethy, 2016).

The importance and necessity of industrial and municipal waste- water treatment have become more apparent in program to conserve and protect vital water resources. A current challenge to professionals in the wastewater treatment field is the potential utilization of effective microbial sources for municipal and industry-based wastewater treatment in the soundest and cost-effective maimer. It is investigated that nearly

1.1 billion people drink unsafe water all over the world (Rajasulochana and Preethy, 2016). As per the reports of the World Bank, around 21% of the communicable diseases in India, are from waterborne (Marshall et al., 2007; Aziz and Mojiri, 2014). The majority of microbial pathogens observed in wastewater treatment plants (WWTPs) are bacteria, viruses, protozoa, algae, fungi, and helminths. The existence of these pathogens in water leads to the spread of various waterborne diseases. The diverse microbial pathogens in wastewater can cause severe chronic diseases with long-term effects, such as stomach ulcer, typhoid, gastroenteritis, and degenerative heart disease. The population density and diversity of these microbial pollutants can vaiy depending on the intensity and prevalence of infection in sewered community (Akpor et al., 2014). The detection, isolation, and identification of the different types of microbial pathogens in wastewater are always laborious, time-consuming, and expensive. To avoid this, indicator organisms are always used to analyze the relative risk of the possible presence of specific pathogen in wastewater (Paillard et al., 2005; Akpor et al., 2014). The major chemical pollutants constitute in wastewater are phosphorus and nitrogen. It is observed that pesticides, detergents, and heavy metals are the most persistent limiting agents in the process of eutrophication (Schultz, 2005; Thawale et al., 2006).

Generally, the process for removal of impurities in wastewater is characterized into chemical and biological process. Chemical removal techniques include coagulation/flocculation, chloramination, chlorination, ozonation, and ultraviolet (UY) light treatment. These techniques involve addition of chemicals to form particles which settle and remove contaminants. The treated water is then decanted and appropriately reused or disposed of after resultant sludge is dewatered to reduce the volume. In the case of biological-wastewater treatment processes, the potential of the microbial community utilized for various wastewater constituents to enhance the microbial metabolism and cell synthesis must be removed before discharge. This microbial metabolic process can effectively eliminate contaminants that are as diverse as raw substances and by-products (Schultz, 2005; Akpor et al., 2014). Many conventional technologies available for wastewater treatments are present for decades (Narmadha and Maiy Selvam Kavitha, 2012; Rajasulochana and Preethy, 2016), but the effectiveness and flexibility of the technology are still challenged. The advancement in new green methods and usage of microbial populations are being popularized to overcome the less effective traditional methods of wastewater treatment (Shivajirao, 2012; Kumar and Sai Gopal, 2015).

Sustainable environmental utilization and conservation have the foremost significance in the present life of mankind. Scientists have been developing new technologies and techniques for the improvement of wastewater management in agricultural and industrial waste. Indigenous microorganisms (IMOs) and effective microorganisms (EMOs) based on technology, which influenced effectively in the eastern part of the world for the enhancement of wastewater management. IMOs are the class of an innate microbial consortium which has potent ability in biodegradation, biocomposting, bioleaching, and nitrogen fixation. EMOs shows specificity in their functional activity and engineered with respect to specific needs for the effective applications hi various areas of biological sciences. The advancement in the wastewater treatment technology leads to usage of these IMOs and EMOs as potential microbial tools for wastewater treatment (Aziz and Mojiri, 2014). Industrial wastewater treatment standards are concerned with the removal of suspended solids, biodegradable organics, and pathogens. Any of the more stringent standards that have been developed recently deal with the removal of nutrients and opportunist pollutants. Hie significant physical factors of the wastewater are the total solids content, which include colloidal matter, settleable matter, and floating matter (Paillard et al., 2005; Kumar and Sai Gopal, 2015). The municipal wastewater is composed mainly of anthropogenic and agricultural wastes that are rich in nutritional supplements such as carbon, nitrogen, and phosphorus. In the meanwhile, it is noted that the cost of biological treatment of wastewater is increasing worldwide due to the population growth in urban and semi-urban areas, such problems have to address by adopting advanced, cost-effective wastewater treatment systems (Aziz and Mojiri, 2014).

The elemental reason for the wastewater treatment is to avoid the impact of water pollution and to protect natural water bodies to get contaminated by hazardous pollutants, thereby safeguarding public health through effective wastewater management against the spread of diseases. This is performed through series of wastewater treatment methods such as activated sludge, stabilization ponds, trickling filters, constructed wetlands, and membrane bioreactors wastewater treatment systems (Haandel and Lubbe, 2007; Akpor et al., 2014). The activated sludge process is one of the efficient bio-nutrient removal methods incorporated in WWTPs. Activated sludge is comprised of various microbial consortia, among which bacterial populations exhibit potent activities in the wastewater treatment process (Aziz and Mojiri, 2014). Microalgae or microphytes are the microscopic algae able to perform photosynthesis similar to plants and reproduce quickly with available nutrients such as phosphorus, nitrogen, and CO, from their environment. As the outcome of photosynthesis, released oxygen is utilized by activated sludge bacteria through the microalgae activated sludge (MAAS) process (Anbalagan et al., 2016; Huijun and Qiuyan, 2016).

The quality and reproducibility of wastewater effluents are responsible for the degradation of receiving water sources, such as rivers, lakes, and streams. Microbial populations are of major importance in treating municipal and industrial wastewater. The application of microorganisms has positive effects on the outcome of aquaculture and irrigation operations. The efficient microbial activities include the removal of toxic materials such as nitrite, ammonia, hydr ogen sulfide, and degradation of uneaten feed (Lu et al., 2009; Huijun and Qiuyan, 2016). These and other functions make microorganisms the key players in the health and sustainability of water bodies. The significant role of various microbial consortium application in the wastewater treatment with specific importance of bacteria and protozoa in removal of nitrogen, phosphorus, and other pollutants observed that microbial mediated wastewater treatment system is very effective and essential to challenge water pollutants especially from municipal and industrial origins (Thawale et al., 2006; Templeton and Butler, 2011; Huijun and Qiuyan, 2016).

INDUSTRIAL AND MUNICIPAL WASTEWATER: SOURCES AND TREATMENT PROCESSES

Environmental pollution due to direct discharge of wastewater into water bodies is a major concern as the components and contaminants of waste are having a hazardous effect on public health and the ecological system. Rapid industrialization and anthropogenic activities are the major sources of contaminants of wastewater (Abdel-Raouf et al., 2012). However, as the industrial wastewater and municipal wastewater have different sources and also various contaminants, wastewater treatment strategies are also different, depends on the properties of wastewater to be treated (Templeton and Butler, 2011). Energy required for the treatment process, sludge generation and disposal strategies, complexity of the process, strength, and adaptability of the treatment, cost-effectiveness, and need of manpower are the important factors directed at the effective process of selection and designing. Though the sources and pollutants of industrial and municipal wastewater are different, they involve overall principles of unit operations and unit processes for the removal of contaminants from wastewater (EPA, 1997; Akpor et al., 2014).

11.2.1 UNIT OPERA TIONS IN WASTEWA TER TREA TMENT

The unit operation consists of physical operations required to eliminate the contaminants present in the water (Kapagiannidis et al., 2012). The screening process involves uses of different types of coarse, medium, and fine screens meant for removal of larger substances from wastewater like rags, paper, plastics, and metals. The screening method is essential in preventing clogging and damage of downstream equipment and processes (Templeton and Butler, 2011). Grit removal, also called primary clarification for both industrial and municipal wastewater, contains different types of grit as domestic and food waste, organic, inorganic, and heavier solid materials (Nannadha and Maiy Selvam Kavitha, 2012). Grit removal facilities usually precede primary clarification and monitor screening.

Quantity and characteristics of grit are crucial factors in the selection of the existing type of grit removal system, for example, aerated grit chambers, vortex or paddle grit, detritus tanks, horizontal flow grit chamber and hydrocyclones (Tchobanoglous et al., 2014).

  • 11.2.2 UNIT PROCESSES IN WASTEWA TER TREA TMENT
  • 11.2.2.1 MICROBE MEDIATED BIOLOGICAL WASTEWATER TREATMENT PROCESS

These set of processes involves biological and chemical conversion of waste. Furthermore, secondary sewage treatment process includes series of unit processes that facilitates biological degradation of sewage with the use of microorganism. In the biological waste treatment process, microorganisms usually use aerobic metabolism to degrade organic pollutants in the liquid sludge (Nielsen et al., 2009, 2010). The objective of microbial degradation of sewage aimed at forcing the resident microbial flora of sewage to degrade organic pollutants for safe treated effluent discharge. The resident microbial flora of sewage plays an important role in effective biological treatment process (Siezen and Galardini, 2008). Understanding the ecology of sewage to explore variety of microorganism’s resident of sewage can play crucial role in designing sewage treatment plants and to carryout effective biodegradation of sewage. Raw sewage contains high biodegradable organic compounds and rich in nutrients, signifies excellent medium to favor the growth of microorganisms (Frigon et al., 2013). Variety of microbes have a different mode of metabolism and decomposing the ability of different pollutants, which allows degradation of different organic waste at once in a treatment plant. Microbes may follow the anaerobic or aerobic mode of waste degr adation. The rate of microbial growth in a particular reactor directly depends on the amount of organic waste present in sewage, and BOD indicates the quality of treated waste- water (Chudoba et al., 1992).

11.2.2.2 ACTIVATED SLUDGE PROCESS

The activated sludge process includes the treatment of sewage using biological floes of bacteria and protozoa and aeration. In this process, dissolved organic compounds are oxidized for nutrient uptake. Sludge is aerated in aeration tank where microorganisms metabolize carbonaceous waste, part of this used to synthesize new cells, and part is oxidized into CO, and water to derive energy (Ahansazan et al., 2014). Cell biomass formed in the reaction are separated from the liquid stream in the form of flocculent sludge while settled biomass in the form of activated sludge returned to aeration tank, remaining forms waste or surplus sludge. A part of activated sludge, the nitrogenous matter is mainly oxidized into ammonia, and nitrogen also added in removing nitrogen and phosphorous (Tadkaew et al., 2010).

71.2.2.3 ATTACHED GROWTH PROCESSES

Hybridized growth processes, in combination with activated sludge and attached growth system, are incorporated into unit processes hr the treatment of sew’age. The attached growth system includes rotating biological contactors (RBC), packed beds, or suspended earner materials, hr general, these systems contain fixed-film components, which safeguards disturbance in the process systems (Gavrilescu and Macoveanu, 2000). An increase in hydrostatic pressure, expulsion of toxic compounds into the system, or breakdown in the aeration system are the demerits of process disturbance. Process disturbance takes account of the principle types of attached growth membranes (Marti et al., 2011).

11.2.2.3.1 Continuously FlowingSuspendedSystems With Fixed Film Growth Membrane

These systems are composed of plastic material and are possible to unite with fixed packing in many cases to maintain unique flow’ patterns. It enhances microbial growth in the fixed film, which is hi contact with wastewater under treatment (Han et al., 2005).

11.2.2.3.2 ContinuousFlowSuspendedWithSuspendedlnternal Packing

These materials designed to float or sink depending on the specificity of the process. These systems enhance the overall interface of attached microbial growth by circulating it into the water treatment column (Marti et al., 2011).

11.2.2.3.3 Sequencing Batch Reactors (SBRs) With Internal Packing

Iii this reactor system, sequential batches of wastewater stored for a period and treated. Batch under treatment seeded with dynamic bacterial culture and oxygenized from the treatment period. This reaction ends with the settling of flocculated bacteria and other solids. The supernatant transferred to the next chamber, the next batch begins, and the cycle repeats continuously (Fang et al., 1993).

11.2.2.3.4 Rotating Biological Contactors (RBC)

It consists of a rotating disc, hence part of fixed film partially submerged per rotation into the flow to react with wastewater under treatment. Process optimization is possible to achieve by adjusting the speed per rotation and depth of submergence (Tawfik et al., 2006; Hassard et al., 2014).

11.2.3 CHEMICAL AIDED UNIT PROCESSES

Chemical treatment processes are utilized to eliminate dissolved inorganic pollutants leftover in secondary biological treatment processes. These processes aimed at the removal of inorganic pollutants from wastewater and maintaining water quality for its safe discharge into the enviromnent (Schuler et al., 2001). Chemical contaminants of water can be removed by changing the temperature or by precipitation as solids carried out by the addition of acid or alkali in the process of chemical precipitation. Maintaining the required pH of the water is the main objective of neutralization, addition of lime, calcium hydroxide, sodium hydroxide, and sodium carbonate are the most common chemicals in use to adjust pH at an acceptable range. Disinfection is the last process of unit processes required for wastewater treatment, and this treatment is conducted by treating the effluent with the disinfectant to inactivate pathogens such as microbes, viruses, and protozoan and to meet the wastewater discharge standards. The ideal disinfectant should be less harmful, and with bacterial toxicity, and should have reliable means of detecting the presence of residues. Chemical disinfectant includes chlorine, ozone, ultraviolet radiation (UV-R), chlorine dioxide, and bromine (Fayza et al., 2007) (Figure 11.1).

General wastewater treatment process

FIGURE 11.1 General wastewater treatment process: (a) Primary wastewater treatment, (b) Secondary wastewater treatment, and (c) Tertiary wastewater treatment.

 
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