EFFECT OF NUTRIENTS ON ALGAL GROWTH AND BIOGAS PRODUCTION

Abstract

The major problems that humanity faces in the 21st century are water quality issues and energy supply. In Pakistan, there are mostly simple dumping grounds that are designated for waste disposal and the resultant leachate is discharged without any treatment. On the other hand, only 8% of the wastewater generated by country is treated, while the rest is discharged into streams without treatment. Adding to the dilemma, present human systems are artificially supported by heavy inputs of nonrenewable energy (fossil fuels) to sustain the materialistic lifestyles. There has been an increasing interest in coupling wastewater and leachate treatment to bioenergy production. Microalgae is a novel green technology that possess very high potential to remove pollutants from leachate and wastewater. It is also being explored as source for third generation biofuel to combat the increasing energy crisis. Hence providing us two benefits at once i.e. leachate treatment & sustainable energy. The objective of this study was to observe the growth of microalgae strains in wastewater and leachate, along with consumption of nitrate and phosphate. Three strains (S4, S5, S6) were collected from ASAB, NUST, while one strain was isolated from a waste water stream. The four microalgae strains were acclimatized and grown in 100% wastewater and 50% leachate. The strain 3 performed well in wastewater with highest average optical density of 2.56, almost 100% nitrate reduction and 57% phosphate reduction during 15 days of growth period. While strain 4 performed well in leachate with optical density of 2.43 with 98% nitrate reduction and 97% phosphate reduction. The overall results indicated their capability to support microalgae growth. The results clearly indicate the possibility of co digestion of microalgae with wastewater and leachate respectively. The resultant algae was co-digested with wastewater and leachate along with cow dung for biogas production. The co-digestion of strain 6 with leachate gave highest methane content of 61.5% and co-digestion of strain 4 with wastewater gave the highest methane content of 57.6% in biogas. The study concluded that coupling microalgae based treatments to bioenergy production has a potential and can be applied in future for sustainable development.