The waste remover in aquaculture ponds

Use your smartphone to scan this QR code and download this article ABSTRACT Over the past decade, Vietnam's shrimp industry has made great progress and brings Vietnam into the rank of the world's largest shrimp exporters. The development trend of the shrimp industry in the world as well as in Vietnam today is in the direction of intensive and super-intensive farming, technology innovation to enhance productivity and quality. However, the shrimp farming industry in Vietnam is facingmanydifficulties; one of them is the problemof environmental pollution, raising negative impact on the economic effectiveness of farming. Causes are mainly due to excess food and untreated shrimp waste, accumulated on the pond bottom surface and disintegrated to reduce dissolved oxygen concentration, release toxic gases such as NH3 , H2S and create a favorable environment for harmful microorganisms to develop. Therefore, it is necessary to have a countermeasure to thoroughly remove waste from the farming environment. This paper introduces a general design of awaste remover, which is needed for shrimp farming ponds to removewaste and solve the mentioned problem. This equipment moves on the bottom surface of the pond and can be autonomous or manually remote controlled. During working process, the equipment brushes waste on the bottom surface of the pond and suck it into the filter bag. Thewaste remover includes such following main units: travelling unit, brushing unit, sucking unit, frame unit, transmission and control systems. The equipment uses the principle of axial pumping, sucks waste along the water stream by reducing the pressure inside the equipment and transfers waste into filter bags. This general design basically meets the requirement of waste removal and can be a fundamental for designing the detailed units, manufacturing and experiment implementation of equipment in the future.1–9


INTRODUCTION
The shrimp pond liner model 35 x 35 m with siphon 2 pit, the paddle wheel systems is the main obstacle that communities, oxygen depletion, and overall degraded 23 water quality 4 . Successful shrimp aquaculture re-24 quires maintenance of water quality conducive for the 25 growth of shrimp. Common water quality concerns 26 for shrimp aquaculture include inorganic suspended 27 solids (ISS), total suspended solids (TSS), biochemi-28 cal oxygen demand (BOD), chemical oxygen demand 29 (COD), dissolved oxygen (DO), and nitrogen 5,6 . A 30 number of physical, chemical and biological meth-31 ods used in conventional wastewater treatment has 32 been applied in aquaculture systems. These meth-33 ods are suitable for tank or small ponds 7 . Mechan-34 ical method of sludge removal may be the solution 35 for commercial intensive aquaculture. In Vietnam, 36 farmers are using sludge pump for removing sludge 37 from fish pond to create healthy environment in the 38 fish pond 8 . A sludge remover was designed and fab-39 ricated at Farm Machinery and Postharvest Process 40 Engineering (FMPE) Division of Bangladesh Agricul-41 tural Research Institute (BARI), Gazipur, Bangladesh 42 with locally available materials. The main functional 43 components of the remover were axial flow pump, en-44 gine, suction pipe, sludge collector with cutter, deliv-45 ery pipe, float, propeller, rudder, crane, etc 9 .   To increase the working time, the equipment requires 98 a large filter bag, so the filter is designed with two 99 pipes suck and two filter bags arranged on either side, 100 the suction mouth is arranged at the bottom of the 101 equipment to suck the waste on the surface of the 102 pond bottom. In order to bring water and waste into 103 the filter bag, it is necessary to select the appropriate 104 type of pump. The waste and water can be suck into 105 the filter bag, but this method must use two pumps. 106 The simpler choice is to use atmospheric pressure to 107 put the water in the filter bag, so the filter bag is placed 108 in the body cavity of the equipment. The axial pump 109 sucked water out of the body cavity through the outlet 110 on the lid of the body. The pressure in body cavity de-111 creased, the atmospheric pressure pushes the flow of 112 water and waste in the body cavity in order to balance 113 the pressure. As such, filter bags and suction pipes are 114 designed to be assembled together by quick couplers 115 for easy cleaning. At the quick couplers need one-way 116 rubber valve to prevent the waste reflux back when the 117 pump stopped working.

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Brush cluster and transmission system for 119 cluster brush 120 There are two methods to brush the surface of the 121 proposed pond bottom lining, the vertical brush shaft 122 (Figure 2a) and the horizontal brush shaft (Figure 123  2b). Regarding the vertical brushing shaft method, 124 the brushing system will consist of two shafts that are 125 rotated in opposite directions by a transmission belt, 126 brushing and pushing water and waste into equip-127 ment chassis. However, this option cause hinders 128 when the equipment overcome obstacles, and the 129 transmission for vertical brushing shaft is more dif-130 ficult than the horizontal brushing shaft. With hori-131 zontal brushing shaft system, the shaft is covered with 132 soft and long enough bristles and is transmitted from 133 the pulley shaft through the gear transmission. Due to 134 the lager transmission, the brushing shaft rotates with 135 large speed to ensure the ability of cleanliness. The 136 waste is also pushed in equipment chassis for suction. 137 The horizontal brushing shafts also supports for the 138 equipment when it overcomes obstacles which are not 139 too large at the bottom of the pond.     The second solution is replaced the GPS with ultra-167 sonic beacon sets, a mobile beacon equipment assem-168 bled on the waste remover and four fixed beacons are 169 placed at the four corners of the pond. The position 170 of the equipment is determined by the four fixed bea-171 cons via an algorithm. In addition, the equipment is 172 equipped with rotary angle and acceleration sensor to 173 adjust when the equipment moves off trajectory. For 174 monitoring location of equipment, four fixed beacons 175 create a pond map, software used to connect the navi-176 gation system to draw the operating trajectory for the 177 equipment, so that it can monitor and control the op-178 eration of equipment on the computer screen.

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Based on the initial analysis, the schematic diagram 180 and the general diagram of the equipment's control 181 system are defined.

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The schematic diagram (Figure 3) illustrates the ar-183 rangement of main components and the motions 184 when the equipment is operating. 200 where M: The mass of the equipment full water.

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From the the initial analysis, the schematic diagram 221 and the general diagram of the equipment's control 222 system, the 3D model of the waste remover is designed 223 by SolidWorks software (Figure 6) and the proposed 224 operating parameters are as follows: At a speed of 15 m / min, the waste remover will op-229 erate a 1000 m 2 (35 x 35 m) pond for a maximum of 2 230 hours and only one operator compared to two manual 231 workers as the current practice. Electricity consump-232 tion in 2 h is 1 kW equivalent to 2.700 VND (high-233 est electricity price) for each pond, which saves labor 234 costs and improves working conditions when shrimp 235 farmers haven't to wade down to the pond to clean the 236 bottom of the pond every day. In addition, the oper-237 ator can do some value creation work while the ma-238 chine is operating in automatic mode. The amount of 239 water filtered in 2 hours is 80 m 3 , so the device will 240 mainly absorb and filter a layer of water about 8cm 241 thick on the surface of the pond bottom, this is the 242 area containing waste deposited should be removed 243 from the culture environment. These results will be 244 verified through the pilot operation of the equipment 245 at a shrimp farm.

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The waste remover was designed, manufactured and 248 tested, met with technical requirements and available 249 for evaluation of operating effectiveness.