AGRICULTURAL MECHANIZATION IN ASIA, AFRICA, AND LATIN AMERICA 2017 VOL.48 NO.1 22 Development of a Paddle Wheel Aerator for Small and Medium Fish Farmers in Nigeria by Omofunmi O. E. Dept. of Agricultural and Bio-Environmental Engi- neering Yaba College of Technology Yaba- Lagos NIGERIA omofunmieric@yahoo.com Adewumi J. K. Dept. of Agricultural Engineering Federal University of Agriculture Abeokuta NIGERIA Adisa A. F. Department of Agricultural Engineering Federal University of Agriculture, Abeokuta NIGERIA Alegbeleye S. O. Department of Fisheries and Aquaculture Federal University of Agriculture Abeokuta NIGERIA Abstract Pond aeration systems were de- veloped to sustain large quantities of fish and biomass materials. In this study the importance and func- tions of aeration were examined and prototype paddle wheel aerator was developed. The main features of the paddle wheel aerator were electric motor used as prime mover which was of one horse power capacity, and paddle hubs with six paddles all mounted on a shaft made of stainless steel and brass materials. Aeration experiment was conducted in water basin made up of plastic. Paddle-wheel aerator performance evaluation was conducted using un- steady state test. Physico-chemical properties of water sampled from the tested ponds were determined in accordance with the American Public Health Association standards (APHA, 2005). Performance test carried out showed that the overall oxygen transfer co-efficient (K L a) was observed to be as high as 8.19 hr -1 and standard oxygen transfer rate (SOTR) and standard aerator efficiency (SAE) ranged from 1.1- 1.2 kg O 2 hr -1 and 1.1-1.3 kg O 2 kW -1 hr -1 respectively. The paddle wheel aerator improved the water quality by addition of oxygen leading to ap- preciable increase in the fish stock density which has been a major set- back of low-income fish farmer in Nigeria. Keywords: Oxygen dissolved, overall oxygen transfer coefficient, paddle wheel aerator standard aera- tion efficiency, standard oxygen transfer rate, water basin Introduction During the past decade, pond aeration systems have been de- veloped which will sustain large quantities of fish and invertebrate biomass. These aeration systems are modiications of standard waste- water aeration equipment. Paddle- wheel aerator is surface aeration system which can be vertical shaft or horizontal shaft that producing a large air-water interface the transfer of oxygen from atmosphere is en- hanced. The importance and func- tions of aeration process is hereby highlighted by some investigators like Boyd (2001, 2003); Omofunmi, 2014; Tucker 2005, and Tucker and Robinson, 1990) include: ● it reduces the concentrations of ammonia, nitrites and carbon (iv) oxide ● it increases pH level of pond wa- ter. ● it increases the carrying capacity of an aquaculture system. ● it reduces ish mortality. ● it enhances ish reproduction sys- tems ● it reduces level of salinity espe- cially during time of low rainfall ● it increases pond productivity. ● it increases ish growth. ● it regulates water temperature especially as this can affect dis- solved oxygen (DO) of aquatic. ● it is used to control thermal strati-