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Publication type: Bachelor thesis
Title: Sun oxygen system : oxygen supply in fish breeding ponds
Authors: Jonathan, Konrad
Advisors / Reviewers: Tschudi, Fridolin
Regazzoni, Luca
DOI: 10.21256/zhaw-22881
Extent: 73
Issue Date: 2021
Publisher / Ed. Institution: ZHAW Zürcher Hochschule für Angewandte Wissenschaften
Publisher / Ed. Institution: Winterthur
Language: English
Subjects: Sun Oxygen System; SOS; Dissolved oxygen; DO; Tilapia; Smiling Gecko
Subject (DDC): 639.8: Aquaculture
Abstract: Fish from aquaculture is becoming increasingly important for global food security. For the Cambodian population, fish is the most important source of animal protein. In 2014, the NGO Smiling Gecko Cambodia was founded. Through cooperation with the Zurich University of Applied Sciences, the Smiling Gecko Fish Project was launched 4 years later. In order to promote the education and income of surrounding smallholder women farmers and to counteract gender inequality, the Woman in Aquaculture project was launched. The Sun Oxygen System (SOS) was developed by the ZHAW to enable the planned fish breeding ponds to be aerated independently of the electricity grid. A pump powered by a solar panel transports the surface water, which is supersaturated with oxygen through photosynthesis by algae, into deeper layers. In this way, the excess oxygen does not immediately diffuse into the ambient air but can be stored for longer by the entire water column. For this work, a feeding trial with Nile tilapias was conducted in two fish ponds (water volume 468 m3) to validate the benefits of the SOS. One pond was operated with an SOS, the other without. Besides daily measurements of dissolved oxygen (DO) concentration, water quality parameters were analysed and SOS performance was monitored. Due to excessive oxygen consumption at night and a clogged SOS pump, the trial was split into two trials. Trial A was started with a fish density of 0.96 kg/m3 (1.7 kg/m2). Trial B was continued with a fish density of 0.5 kg/m3 (0.9 kg/m2). The daily DO concentrations of the two ponds recorded during Trial B showed a 0.48 kg higher oxygen input during the day in the pond with SOS. However, this increased oxygen input was used up again overnight, so that the morning DO concentration with SOS was always lower from the 5th day (Trial B) of the trial than without SOS, and from the 7th day (Trial B) onwards no longer rose above 1 mg/l. Weighing the fish did not yield any useful data, as the feeding trial was stopped early in both trials due to the DO concentration being too low. The sample size of the weighed fish in both trials was considered too small to calculate a representative average weight, as the scatter of the weights was too large. Daily DO concentration curves were used to show the effect of SOS on pond water mixing. While without SOS a stratification with different DO concentrations takes place, with SOS the DO concentration is balanced in the evening. An analysis of the SOS performance showed that on sunny days a power surplus of 0.86 kWh is produced, which can be used for additional energy consumers. The reasons for the high oxygen consumption overnight were then discussed. Possible solutions were identified and design changes were proposed for further SOS tests.
License (according to publishing contract): CC BY 4.0: Attribution 4.0 International
Departement: Life Sciences and Facility Management
Appears in collections:Bachelorarbeiten Umweltingenieurwesen

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