The Research Of Fine Particles Removal Techniques In The Seawater Recirculating Aquaculture System

Since the21st century, water shortages threatening the production and life of manyregions of the world. Traditional extensive aquaculture production not only to competewith human resources, but also cause their own water and pollution of the surroundingenvironment, because the aquaculture wastewater contains particulate solid waste,dissolved metabolic wastes, nutrients, anti-microbial agents and drug residue will;Accordingly to change the mode of aquaculture imperatively. Recirculating aquacultureis an important way to to achieve efficient, green and clean fish production,industrialized recirculating aquaculture is one direction of the aquaculture development,is a pillar technology of industrialized recirculating aquaculture in the future, this trendmade more stringent requirementsof circulating water treatment process. In recent years,under the support of many national projects, seawater industrialized recirculatingaquaculture has been promoted and applied on a larger scale, In Shandong、Liaoningand other places have been gradually showing a trend to replace traditional farmingmodel. However, the current practical application situation shows that, most of theactual production capacity of the system did not meet the original design specifications,remains in low-density working conditions. Analysis of the reasons, the fine particles（≤60μm） do not get good control and removal which is a major problem. For thisstudy on seawater recirculating aquaculture systems to remove fine particles technologywill provide technical and theoretical support from a different perspective for the furtherdevelopment of the aquaculture industry.The paper, in the laboratory we design of two devices in the actual breedingenvironment: an impeller type (also known as the rotor broken gas type) flotation device and airlift sand filter, in seawater recirculating aquaculture industry dealing withphysical filtration treatment, get the actual treatment effect, water quality sampling, datacollection, data analysis ultimately be dealt with the effects of two devices, thepredecessors of the device and compare the treatment effect, draw some conclusionsand put forward my own views,and expected to make some contribution for theaquaculture industry.Impeller flotation device includes a motor, spindle, support tube, bubble occurs,top and bottom cover, motor support base and other several parts assembled, the thesisof the selection and design of some parts has rigorous calculation and selection. Afterthe prototype design is completed, the water recirculating aquaculture systemsworkshop tested and corrected more than two months, get a lot of water to process data.Tests showed that this simple impeller flotation device structure, low energyconsumption, stable system operation, small motor noise, improve the farmingenvironment; through data analysis shows that this impeller flotation devices for seawater recirculating aquaculture systems water particles suspended solids (SS) in theintake valve controlling the intake air pressure is10m3/h, HRT is the best deal under25min conditions, the average removal rate was42.13%; the system uses YSI waterquality parameters dissolved in water tester oxygen (DO) for data acquisition andanalysis, concluded that the impeller-type flotation device pool of dissolved oxygenfrom6.18mg/L to6.83mg/L, SS removal of visible devices but also can effectivelyincrease the dissolved oxygen. Impeller flotation device chromaticity, TN (TN), CODremoval have some effect, the average removal rate were16.93%,32.64%,32.69%, itis worth mentioning that the ammonia water for farming nitrite removal ineffective. Thepaper impeller flotation device designed experimental test has a certain value; I believewill provide some help for the research aspects of factory aquaculture water treatmentplant.Traditional pressure sand filter after long time working intercepts large amounts ofsolid particles and leads to difficult backwash，in order to solve this problem, the research optimize the equipment based on the original one and developed a airlift sandfilter that can backwash itself while operating；Airlift sand filter set filtration、separation、flotation、self－cleaning and other functions in itself, could replace thetraditional sand filters、filter cell without valve、mechanical air flotation and otherphysical filtration device in aquaculture workshop；Test apparatus used quartz sand (1～2mm) as the filter medium，the aquaculture sewage flowed upward slowly from thebottom，then quartz sand intercepted the suspended solids；Meanwhile，the fixed flowgas flowed from the bottom that made the dirt and quartz sand were institutedsimultaneously，during this process，sand and water were sufficient contact in theequipment，since interaction force between the sand and seawater, a large number ofbubbles are resulted，suspended solids were wrapped with bubbles，quartz sand wascleaned by the sand washing device on the top of the system，due to the action ofgravity，sand fallen into the system，suspended solids and waste water out flow from theoutfall；the research showed that，airlift sand filter equipment has the advantages ofsimple equipment、convenient operation, backwash without stopping the equipment,smooth and continuous system running， low energy consumption and easy tomaintenance and repair；data show that，this sand filter for marine recirculatingaquaculture systems of the suspended solids (SS)and chemical oxygen demand (COD)removal efficiency is41.31%、34.04%；before the text，the number of large particlessuspended solids (60mu m or higher) was11.1%, its mass fraction was71.77%and itsmass concentration was93.53㎎/L; However, after the water has been processed, thelarge particles suspended solids were decreased in number and mass fraction,respectively0.68%and38.07%, and its mass concentration reduced to15.72㎎/L; atthe beginning of the test, the number of micro particles (60microns or less) was88.92%,its mass fraction was28.23%, and its mass concentration was as high as36.79㎎/L,after the experimental treatment, the micro particles that below30microns accountedfor87.45%, its number of mass fraction was13.61%, and its mass concentration was5.62㎎/L, as we can conclude from the result, the effect of particulate removal treatment is significant; at the same time，it also reduces the content of ammonianitrogen，nitrite in the system，after filtration，the suspended solids in recirculatingaquaculture systems is≤67.33㎎／L that meet the requirements of the watertreatment in marine recirculating aquaculture workshop.This study aims to use these two flotation and sand filtration techniques, and get asuitable removal fine particulate process in seawater recirculating aquaculture system,to design special aquaculture water treatment equipment. Expected to provide referencefor the further development of the domestic recirculating aquaculture technologyupgrade.