The Study of the Effects of Flow Rate on the Physiochemical and Microbial Properties of Aerated Compost and the Growth Promotion of Brassica Rapa (Dwarf Bak Choy)

Lim, Keith Khay Yan (2022) The Study of the Effects of Flow Rate on the Physiochemical and Microbial Properties of Aerated Compost and the Growth Promotion of Brassica Rapa (Dwarf Bak Choy). Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Microbial composting is a method of waste treatment where organic wastes are processed mainly by the microorganisms. Aerated composting is used where airflow is induced through the mix of materials using an electric blower. The microbial composting process uses microbes to produce carbon dioxide, heat and leachate from the compost and the composting process requires oxygen as the microorganisms undergo aerobic respiration in order to carry out the process. The microorganisms will affect the soil ecosystem and function as they have an important role in the soil as they help in the decomposition of organic matter, and nutrient cycling as well as plant nutrient availability. The entire aerated composting process aims to convert organic material into stable material with the production of fibre-rich carbon containing humus which is rich in inorganics such as nitrogen, phosphorus, the final product of the compost can be used as fertilizers and soil amendments. The objective of this experiment is to investigate the optimum air flow rate in an aerated compost and the effects of different air flow rate in physiochemical properties of the compost. To investigate the effects of different air flow rate on the compost affecting the growth of the Brassica Rapa as well as the microbial composition in the compost. There are 5 flow rates in this experiment which are 0,10,15,20, and 25ml/min. The microorganisms were collected at the beginning and end of the experiment for the quantification of the microbial population. The differences between the abundance of microbe were quantified as CFU/g of the compost, the compost with the aeration rate of 20ml/minute shows a decrease in CFU/g while the others showed an increase. The selected bacteria species that are tested for are Rhizobium sp., Pseudomonas sp., Salmonella sp., Escherichia coli, Azotobacter sp., and Enterococcus faecalis sp., and tested with gram-staining, KOH test, Methyl-red test, vogues-Proskauer test, catalase test, citrate test, and Eosin methylene blue test, chloramphenicol and ampicillin antibiotic test for further testing. The compost sample was analysed physiochemically and shown that the nitrate content in the compost increased as the aeration increased to a certain extent. After the composting process, the compost was mixed with sand and used to plant Brassica Rapa and grown for 4 weeks. The growth of the plant was measured and taken at the starting and the end of the experiment shows that the compost with the 20ml/min has the greatest growth overall