Study On Acoustic Detection Of Residue In Aquaculture Water

With the global economic development and population increase,people's demand for aquatic products is also booming.In this trend,the aquaculture industry in China has developed rapidly,and the scale of aquaculture has been improved.Industrialized recirculating aquaculture is gaining more and more applications due to its high degree of intensification,breeding environment and controllability of wastewater discharge.While recirculating aquaculture brings high yield at the same time,aquaculture wastewater also damages the water environment and is not conducive to sustainable development.The main pollutants in the process of mariculture are two kinds of sources: external pollution and internal pollution.Exogenous pollution,including the system of fertilization,feeding,adding anti-disease drugs.Endogenous pollution includes biological debris,animal excreta and contaminants attached to the sediment.In aquaculture industry,food costs generally account for 50% to 80% of the total cost.In breeding process,if the amount of feeding is not enough,it will lead to fish weight loss and slow growth;if the amount of feeding is too much,then it causes waste of food,pollution in the farming environment.By monitoring the feeding process of aquaculture,the benefit of meeting the growth of aquaculture growth while effectively reducing food waste,is not only to save farming costs and reduce feed coefficient,but also to avoid excessive feeding and excessive bait,and causing aquaculture water environment pollution.In recent years,automatic feeding machine is widely used in aquaculture,especially in industrial circulating water aquaculture because of feeding precision,uniformity,reducing labor costs,etc.However,automatic feeding machine can only set the amount of feeding in advance,the food taken by fish changes due to weather,water temperature,water quality,breeding organisms and other factors.If not timely adjust the amount of food feeding,it is easy to cause food waste and deterioration in aquaculture water quality,therefore,a device can be applied in the process of aquaculture,which can timely monitor feeding residues in the process of feeding and feedback to the automatic feeding machine to timely adjust feeding amount.In underwater transmission,ultrasonic has advantages like high sensitivity,good direction,massive energy,strong penetration and etc.,so it is widely used in underwater communications.In this study,ultrasonic detection work system?including transmitter,transducer,receiver?were placed in the inlet of the solid-liquid separator out of the pond,fixed to the water surface and submerged in water.Use the amount of the bait in the pond which are detected to judge whether the feeding is excessive,and use the tethered method to measure target strength?TS?of the single bait and multiple baits.The main conclusions are as follows:?1?Change the transmission voltage between 0V 10 V to test the linear region of the system,found that the sensor response with the voltage is a linear relationship.?2?Experiment determined that the source voltage amplitude is 6V,triggering interval is 300 ms,and each cycle launches 30 sine pulse.?3?Under the water,the reflection voltage of the small steel ball meets: E²=P₀²Me²G²?1/R⁴?10^-?R·TS·D²???Use a small steel ball of which the target strength is known to determine the the coefficient in the function.?4?In the experiment,two kinds of baits with diameters of 11 mm and 9mm were used to measure the peak-to-peak voltage amplitude value of the reflected echoes of the bait and the mean value of the interval decreased of 3d B from the maxinmum voltage value.The results show that there is no obvious reflection echo of single bait,the echo is too small to be measured,and it is difficult to calculate the target strength of single bait.Multiple bait experiments were conducted,and the scattering intensity of the bait was divided by the number of particles to obtain the target strength of the single bait.The results showed that the maximum value of target strength?TS?was-6.979 d B,mean value was-5.313 d B for No.11 bait?diameter of 11mm?,and the maximum value of target strength?TS?was-3.642 d B,mean value was-2.666 d B for No.9 bait?diameter of 9mm?.The curve of the relationship between square of max value and mean value and the number of particles showed that it was a linear relationship between the two.For No.11 bait,x11 represents number of particles,y₁ represents the square of max,y₂ represents the square of mean,the expression was showed as max:y₁=21.312x11-31.036 and mean: y₂=16.857x11-25.301.For No.9 bait,x9 represents number of particles,y₃ represents the square of max,y₄ represents the square of mean,the expression was showed as max: y₃=5.9964x9+5.6346 and mean: y₄ = 4.3854x9+4.2436.In the case of the same number of particles,the reflected voltage amplitude value of No.11 bait was bigger than the No.9 bait,indicating that when other conditions are the same,the greater the measured object size,the greater the target strength.Comparing the slopes in y₁ and y₃,21.312 and 5.9964,we can conclude that the max voltage of No.11 bait increases with the number of particles faster than that of No.9 bait.Comparison the slopes of y₂ and y₄,16.857 and 4.2854,we can conclude that the mean voltage of No.11 bait increases with the number of particles faster than that of No.9 bait.This study tries to use volume scattering intensity detected to measure residual bait content in the aquaculture water.And the relevant parameters of the detection system were determined experimentally,so as the target strength of a single bait.The experiment provides a theoretical basis for the technique of precise feeding in the industrialized recirculating aquaculture and also provides the technical support for the accurate feeding in the process of industrialized recirculating aquaculture,optimizing the environment of aquaculture water and reducing the discharge of pollutants.