Abstract
Six different concentrations of Chlorella vulgaris microalgae culture are incorporated with raw wastewater to improve treatment efficiency in three phases. In phase one of study, 30% and 40% microalgae were incorporated with raw wastewater with 24 hrs retention period for 18 days in a batch mode and these conditions are made same for all phases. During phase two and phase three of study, 20%, 25% and 35%, 45% micro-algae concentrations used to treat raw wastewater respectively. Amongst all the six concentrations, 30% microalgae behaves most efficiently and is able to reduce 34 to 81% COD, 43 to 75% nitrate, and 36 to 99% of phosphorous. Overall ammonia nitrogen reduction varies from 80% to 99%. No attempt was made to control temperature or evaporation losses. These attempts can definitely increase the growth process of microalgae and increase the removal efficiency of nutrients in wastewater.
TopIntroduction
As the population increases demand for freshwater also increases and most of the water is fit for drinking purposes. Conventional waste water treatment processes are less efficient in removing Nutrient in form of Nitrogen and phosphorous (Migliaceio et al., 2009). Discharge of wastewater with elevated quantities of nitrate and phosphates contributes to eutrophication in waterbodies. It has been observed as significant water pollution (Tredici et al., 1992). Costal eutrophication causes higher mortality rates in aquatic species, and enhanced organic particle sedimentation (Driscoll et al., 2003). In this process, microalgae consumes nutrients and carbon dioxide, generates oxygen for aerobic microorganisms. Microalgae biomass can be utilized for bio-fuel extraction because of its rich fatty acid content (Sheehan et al., 1998).Microalgae survives easily in water enriched with nutrients this ability of microalgae signifies its importance in wastewater treatment and can be a incorporated with conventional wastewater treatment systems (Ruiz et al., 2011).Microalgae can utilizes organic carbonaceous matter for cell synthesis (Wang et al., 2010).Various kinds of algal species starting from single-cell to progressively complex multi-cellular structures, amongst which microalgae are widely available in various situations. Photosynthesis and growth rates of microalgae are comparatively higher than other plants present on land surface (Li et al., 2008). The most widely accepted microalgae strains used for treating wastewater are Chlorella and Scenedesmus (Garcia et al., 2000). Chlorella species and tolerant flexible and can be harvested physically and bio-mechanically under different wastewater conditions. Algal wastewater treatment method helps to remove nutrient and provide oxygen as a by-product in the system which is not only reduce the aeration demand also provide oxygen to aerobic microbes
Key Terms in this Chapter
Turbidity: It is the degree to which transparent liquid scatters light. Turbidity causes due to very small particle which are normally not visible to naked eye.
Chemical Oxygen Demand: It is the amount of oxygen required to consume all biodegradable and non-biodegradable organic matter.
Nutrients: Essentially required for growth of any living organisms. Plants required 11 types of compound for the growth process. Majorly 3 compound N-P-K (nitrate, phosphate, potassium) are essential for plant growth. These are commonly known as plant nutrients.
Photosynthesis: It is a process followed by plants in which light energy converted to chemical energy which supports the plant growth. It is a natural process.