Experimental operation and performance evaluation of waste remover in aquaculture ponds

Use your smartphone to scan this QR code and download this article ABSTRACT The development of new technologies in automation to increase labor productivity has been increasingly enhanced in recent decades. The problem of cleaning water in shrimp ponds greatly affects the quality as well as shrimp production. Environmental pollution of shrimp farming is a matter of concern because the current waste treatment solutions are not yet thorough. A waste remover of shrimp waste combined with pond bottom siphon method has been researched and developed to increase the ability to thoroughly handlewaste generated in the culture environment. This device helps to automate themanual cleaning of the pond bottomby farmers. The device performs operations to clean waste, suck, filter and remove waste from the culture environment. This device is self-propelled or manually controlled and operates in all weather conditions. This article introduces the process of testing and evaluating the efficiency of waste extraction equipment in shrimp ponds. The device was tested at a super intensive shrimp farm and evaluated for operational efficiency. The experimental model consists of a shrimp pond operating a waste suction device, a control pond, an automaticmonitoring system of water quality parameters (DO, H2S, NH3 , pH and temperature). Experimental ponds operating waste disposal equipment, control ponds are manually cleaned, other farming conditions of the two ponds are similar. The impacts of waste on shrimp culture environment are determined through analyzing the results of measuring water quality criteria in the pond, thereby assessing the efficiency of waste removal of the equipment. The measurement results show that water quality parameters reach a value within the threshold if operating a waste suction device once per day. The benefits of waste remover operate are to help save the cost of labor to clean the pond bottom, protect workers' health.


INTRODUCTION
Brackish water shrimp farming is an important eco-2 nomic industry of Vietnam with current export in 3 amount of USD 3.85 billion and expected export in 4 2025 is USD 10 billion. 5 To increase productivity, high tech intensive and sup- 6 per intensive shrimp farming methods are imple-7 mented to production practice with increasing pro-8 portion. 9 The area of high-tech shrimp farming is planned to be 10 100,000 ha in 2020.

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The main features of high-tech shrimp farming are us- surface. This layer of the organic material also be-21 comes the favorable environment for harmful bacte-22 ria to grow. It is observed that there is a sticky, slip-23 pery layer on the surface and it is not easy to be re-24 moved just by water flow caused by paddle wheels. 25 Most of the waste is collected in the siphon pit, but 26 the rest need to be removed from the pond. Sig-27 nificant sludge buildup may negatively affect the tar-28 get crop by increasing biological oxygen demand, re-29 ducing usable habitat, decreasing availability of natu-30 ral prey organisms and releasing toxic compounds 2 . 31 Typically, effluents from aquaculture are character-32 ized by increased nitrogen species (ammonia, nitrites, 33 and nitrates), organic carbon, phosphates, suspended 34 solids, and high biological oxygen demand (BOD) 35 and chemical oxygen demand (COD) 3 . Significant 36 issues can result in the release of nutrient rich efflu-37 ents such as these including increased algal blooms, 38 degradation of benthic communities, oxygen deple-39 tion, and overall degraded water quality 4 . Success-40 ful shrimp aquaculture requires maintenance of wa-41 ter quality conducive for the growth of shrimp. Com-42 mon water quality concerns for shrimp aquaculture 43  The schematic diagram (Figure 2) illustrates the ar-97 rangement of main components and the motions 98 when the equipment is operating.

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The control system of the waste remover (Figure 3) 100 uses two microcontrollers on the central control 101 board and the control board communicates with each 102 other and receives control information from the user 103 and executes control commands for three motors.

Trial run and evaluation
105 Experiment is carried out in 2 shrimp pond in Can 106 Gio District of Ho Chi Minh City; from these 2 ponds, 107 1st is experimental pond, and 2nd pond is controlled 108 pond.

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Experimental conditions are listed in Table 1.

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Water quality 114 During testing period, water quality parameters, such 115 as dissolved oxygen (DO), temperature, pH, and con-116 centration of H 2 S, NH 3 are measured 7 .

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The condition of measurement such as: equipment, 118 sensors, and frequency are listed in Table 2.

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There is no temperature adjustment equipment then 120 water temperature depends on the environment tem-121 perature. Water temperature during experiment var-122 ied from 28 o C to 32 o C, and is the same in both ponds. 123 Dissolved oxygen is adjusted by aeration equipment 124 and it is kept the same in both ponds, in level from 125 4.0 ppm to 6.8 ppm. 126 pH is adjusted by adding calcium oxide (CaO) and 127 molasses to keep this value the same in both ponds 128 and in level from 7.5 -8.0. Adding calcium oxide 129 (CaO) and molasses is carried out twice a day, at 6:00 130 am and 17:00 pm.

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Probiotics are added to the both ponds in the same 132 scheme.

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Siphon and water change is the same for both ponds 134 during testing period.

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The results of H 2 S measurement during 15 days show 136 that water does not contain H 2 S. This is explained by 137 fact that there is very little sludge accumulation at the 138 bottom because bottom is cleaned daily manually or 139 by waste remover.

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The NH 3 measuring results (ppm) during 15 days are 141 presented in Figure 4.

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Statistical data of NH 4+ measurement results is listed 143 in Table 3.     The planned sale price is USD 8000 and then equip-163 ment is paid back after one year.

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Using waste remover twice daily to improve water 165 quality requires additional study.

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-Waste remover can work well on HDPE shrimp pond 168 bottom.

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-1 time per day cleaning by waste remover gives the 170 same water quality in comparison with manual clean-171 ing.

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-Waste remover can save worker's health and help to 173 solve the manpower shortage.

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-Waste remover expected to be paid back after 1 year. 175 -Additional study is required for 2 times cleaning us-176 ing waste remover to improve water quality and elec-177 tricity saving.