Study on Circulating Aquaculture Water Treatment Based on Micro-electrolysis

Transcription

1 145 A publication of CHEMICA ENGINEERINGTRANSACTIONS VO. 55, 216 Guest Editors:Tichun Wan, Honyan Zhan, ei Tian Copyriht 216, AIDIC Servizi S.r.l., ISBN ; ISSN The Italian Association of Chemical Enineerin Online at DOI: 1.333CET Study on Circulatin Aquaculture Water Treatment Based on Micro-electrolysis Zhaoxue Wu, Qian Wan, Yinchun Yan, Chenmao Cao* Collee of enineerin, Anhui Ariculture University, China chenmaoedu@mail.com We verified the effects of micro-electrolysis technoloy on the treatment of aquaculture water, and studied the chane of the water quality parameters and the rowth situation of the fish in the process of micro-electrolysis treatment simulated the aquaculture water in the recirculatin aquaculture system, and verified the feasibility of micro-electrolysis technoloy applied to circulatin aquaculture water treatment. At the same time, the rowth situation of fish was also tested. The results showed that micro-electrolysis could effectively remove ammonia nitroen and maintain the stability of water quality parameters. The fish weiht kept increasin durin the culture, and there was no sinificant difference compared with the theoretical increase. 1. Introduction In the recirculatin aquaculture system, the rapidly accumulation of TAN (total ammonia nitroen) is caused by the decomposition of fish excreta and food residues. In the aquaculture of the recirculatin water system, the breedin density is hih and the water volume is limited, which will lead to the rapidly deterioration of the water quality of the aquaculture, and this problem is particularly important in circulatin water culture. In addition, the nitrification efficiency of the biofilter in seawater is lower than in fresh water. Since non-ionic ammonia and nitrite are hihly toxic to fish, it is necessary to adopt new techniques to avoid the accumulation of these toxic compounds and to achieve the effective removal, which is necessary to consider the reuse of aquaculture water to reduce environmental problems and save operatin costs. The water treatment technoloy is an important part of the cycle of aquaculture and the key factors to determine the success of farmin. We use the water treatment technoloy combined with the micro-electrolysis to carry out research on recycled water. 2. Materials and methods 2.1 Experimental materials and equipment The cultivation object is Gifu Tilapia. Granularity aquaculture feed (fish meal, summer rain, peanut money, squid thorn, hih-luten flour are as the main raw material). UV-visible spectrophotometer, Seven-Multi-type ph ORP Conductivity eneral-purpose tester, BSA822 electronic balance; sterile console, autoclave, constant temperature incubation, PVM-3 multi-filter, AP series of vacuum-free without candle diaphram, water bath, thermometer (-4-5 C), portable turbidity meter (HACH21P, Hach), stabilized voltae supply, UV, titanium-based platinum electrode; lutamate acid deaminase, transaminase and carbonic anhydride kit. 2.2 Testin apparatus The recirculatin aquaculture system based on micro-electrolysis is shown in fiure 1. The size of the fiberlass aquaculture pond is φ8mmx75mm; the flow rate of the catastrophe splitter is 1 h; the combined electrolytic cell (the outer cylinder size is φ3mm, the inner cylinder size is φ2mm, the power of two ultraviolet lamps is 16w, the size of electrode slice is 25x15cm); The size of the buffer tank is 1x3x5mm, activated carbon filter (the hih is 125mni, in which the quartz sand layer is 15cm, the fine carbon layer is 9mm). Please cite this article as: Wu Z.X., Wan Q., Yan Y.C., Cao C.M., 216, Study on circulatin aquaculture water treatment based on microelectrolysis, Chemical Enineerin Transactions, 55, DOI:1.333CET165525

2 146 Fiure 1: Micro-electrolysis test system device diaram 1, breedin pond 2, pot spin separator 3, drawin box 4, combined electrolysis cell 5, bulkin tank 6, pump 7, activated carbon filter 2.3 Experimental methods 1) Preparation of aquaculture water In the industrial circulatin water channel, before flowin into the pond, the sea water needed to add a certain amount of fresh water to adjust the water temperature, and the sea water salinity was about 25 or so after adjustin. Therefore, the aquaculture water in this experiment was prepared by addin seawater into tap water so that the salinity reached 25, the ph value was , and the fry was placed in the pool after 24 hours. The ammonia concentration of simulated wastewater reached 5m or so by addin 1 chlorination. 2) Tilapia domestication Gifu Tilapia is a ood stock that after years of efforts, the Philippine aquaculture experts use the traditional breedin methods combined with bio-enineerin technoloy to cultivate and the breedin materials are four species of Asian Nile tilapia and four species of European Nile tilapia, named Nile tilapia "Jifu strain." The time for domesticatin the Tilapia used for testin is 5 days. The specific method of domestication is in a recirculatin aquaculture system (the size of the culture pond is φ2m, and the depth of water is 6cm), the salinity is improved 1 per day to 25. The fish is fed accordin to 1% of the fish weiht durin the domestication. The daily water exchane rate is 5%, and the salinity should be maintained stable. Aquaculture pond uses the aerated poly to increase oxyen, and the water quality indicators durin the days is that the water temperature is 23 ~ 27, ph is 7.5 ~ 7.9, and dissolved oxyen is 6. ~ 9.m. The body weiht of the fish was determined after the domestication was completed, and the fish was transferred into the experimental pool for breedin experiment. 3) Tilapia feedin There were 21 tilapias in each pool. The averae weiht was 25 ± 5, and the daily feedin amount was 3% of the weiht. After that, the feed amount was increased accordin to the increase of the theoretical weiht, and the feedin time respectively is 9:, 13: and 18:. The rest of the materials timely remove and weih. 4) Electrolytic conditions Accordin to the "hypochlorite steel enerator GB ", when 1A h of electricity went throuh the electrolyzer in diaphramless electrolytic, the theoretical production of available chlorine was a certain value. At the same time, accordin to the Faraday's law of electrolysis, the electrolytic conditions in the second chapter was amplificated to determine the electrolytic condition of this experiment was (15V, 2.5A), the ratio of electrolysis to direct reflux was 1: 2, and the electrolysis time was 5h day (9: ~ 14: ). 5) Water quality index detection Three samplin points were set in the system. The samplin point 1 was located in two aquaculture ponds. The samplin point 2 was located at the outlet of the electrolyzer. The samplin point 3 was located in the buffer tank. PH and ORP (redox potential) were determined by multifunction Ph. The residual chlorine was determined by UV spectrophotometri. The ammonia nitroen, nitrite, nitrate were determined by usin the national standard method, and the system chaned 5% water every day. 6) Tilapia rowth situation The Tilapia weiht rowth durin culture can be expressed as follows: temp [ ( Β C W ) ] t = W e days (1) W was the initial weiht of tilapia, and Wt was the tilapia weiht after t days.

3 2.4 Data processin The drawin was completed by usin excel software to analyze, SPSS was used for analysis of variance, the results was expressed as mean ± standard deviation. 3. Results 3.1 The chane of water quality parameters of simulated circulatin aquaculture system Before the aquaculture experiment, the chlorinated inot was added to the sea water to make it reach the concentration of 5m. The electrolysis time and electrolysis power were determined by simulatin the chane of the water quality parameters and the removal efficiency of ammonia nitroen durin the electrolysis of the wastewater. The voltae was 15V, the current was 2.5A, the proportion of electrolysis part and direct reflux part was 1: 2, and the electrolysis time was 3h. The chane of ph, ORP, residual chlorine, ammonia nitroen, nitrite nitroen and nitrate nitroen in the aquaculture water after electrolysis were shown in Fiure 2 to Fiure V m 7 p H Fiure 2: The chane of ph durin the simulated electrolysis of aquaculture water From Fiure 2, it can be seen that the ph decreased rapidly to 6.78 when the pond water flowed throuh the electrolyzer. When the water in electrolysis cell was dischared into the buffer tank, the ph was kept at 7.15 due to mixin with the non-electrolyzed aquaculture water. After the buffer water went throuh the activated carbon filter, the ph value is rapidly increased because of the adsorption of the activated carbon, but it will be slihtly lower than that of the previous culture pond. In eneral, the ph of the pond water decreased from 7.68 to 7.53 in the process of electrolysis. So the electrolysis will lead to ph reduction in the breedin pool, with the prolonation of the electrolysis time, ph value decreased more obvious. In the actual breedin test, the bakin soda should be added or the medical stone should be put in the buffer pool to adjust the ph of breedin water to ensure the stability of ph ) V 2 (m P R O Fiure 3: The chane of ORP durin simulated seawater electrolysis As shown in Fiure 3, the ORP was reduced to about 17 mv when the pond water flowed throuh the electrolytic cell. When the electrolytic cell effluent enters the buffer slot, ORP remained at about 275 mv due to mixin with the untreated aquaculture water; After the buffer water went throuh the activated carbon filter, ORP decreased rapidly because of the adsorption of the activated carbon, but the ORP in oriinal breedin

4 148 pool remained basically the same; overall, in the electrolysis process, ORP of the breedin pool water remained at 231mV or so. As a result, the ORP of the breedin pool is almost constant durin the electrolysis m 8 e rin lo 6 l c h a u 4 s id e R Fiure 4: Chane of residual chlorine in the process of simulated aquaculture water electrolysis As shown in Fiure 4, the effective chlorine concentration increased rapidly when the aquaculture pond water flowed throuh the electrolytic cell, especially in the first 3min, the hihest rate reached 6.45m, then kept risin trend, and reached 11.34m at 18min. When the effluent of the electrolyzer flowed into the buffer pool, the residual chlorine increased from the 24m after leakae because of mixin with the nonelectrolysis of the pond water. After the buffer water went throuh the activated carbon filter, the residual chlorine quickly dropped to about 2m because of the adsorption of the activated carbon. From the overall view, the residual chlorine of the aquaculture pond water remained l ~.5m, which lower than the tilapia Semi-lethal concentration Ṉm 3 + H 4 N Fiure 5: The chane of ammonia nitroen in the process of simulated seawater electrolysis As shown in Fiure 5, when the simulated wastewater flows throuh the electrolytic cell, the combination of electrolysis and UV produces dwarf radicals and chlorine radicals as well as direct electrochemical oxidation, which accelerate the removal of ammonia nitroen. The concentration of ammonia in 12 min rapidly decreased from 5.89m to 1.26m. The concentration of ammonia nitroen in buffer pool and the culture pond chaned little in 6min, but decreased rapidly after 6min, and decreased to.7m in 18min. One-way ANOVA was used to analyze the concentration of NH3-N in the culture water at different time points. The results showed that the concentration of NH3-N in the buffer pool and the culture pond was not much different, but the concentration of NH3-N was hiher than that in the effluent of electrolytic cell, which indicated that the removal of NH3-N was mainly due to the direction electrolysis oxidation in the electtrolyzer. But the concentration of available chlorine was low in the bulkin tank, and the indirect electrochemical oxidation was weak, which had no effect on the removal of NH3-N. In eneral, 5m ammonia nitroen in the culture pond rapidly reduced to below 1m, which will not have an impact on the normal rowth of fish.

5 Ṉm 1 - O 2 N Fiure 6: The chane of nitrite nitroen in the process of simulated seawater electrolysis As shown in Fiure 6, the concentration of nitrite increased with the prolonation of electrolysis time when the aquaculture water flowed throuh the electrolyzer, and reached the maximum at about 15 min, which was about.76 m. As the electrolysis time continued to prolon, the concentration of the nitrite started to decrease rapidly, and decreased to 12m at 24min. The chane of nitrite nitroen in the buffer pond and culture pond chaned almost the same as in the electrolytic cell, and the nitrite nitroen concentration in the culture pond was always lower than that in the electrolyzer and buffer pool in the first 15min, that is, the denitrification of the part of the nitrate occurred in this process Ṉm.8 - O 3 N Fiure 7: The chane of NO3-N in the process of simulated seawater electrolysis It can be seen from Fiure 7 that the concentration of ammonia and nitroen in the culture ponds, electrolyzers and buffer pools increased durin the first 6 min in the water treatment of the combination of electrolysis and UV, but the difference was not sinificant. With the prolonation of the time, the concentration of NO3-N of the H samplin location showed a certain differences that it was the hihest in the electrolyzer, followed by in the bulkin tank and it was lowest in culture pond. The concentration of NO3 - N in the culture pond reached 1.23m at 24min, while the concentration of NO3 - N at 3m did not affect the rowth of the culture objects in the actual breedin process. 3.2 Increase of the fish weiht durin breedin At the beinnin of the breedin, the fish were sampled at random in each culture pond and the body weiht was measured. The body weiht was then measured every 1 days in the same manner, and the theoretical body weiht ain of the fish was calculated accordin to 2-1. The result was shown in Fiure 8:

6 15 Theoretical increment Virtual increment h fis f 31 o h t i e 29 W Datedays Fiure 8: Body weiht ain of tilapia durin culture test Durin the 3-day culture period, tilapia's body weiht kept increasin, but the rowth was less than the theoretical rowth. At the end of the culture, tilapia weiht was 9.3 ± 1, which was lower than the theoretical value of 12. This is partly due to the fact that the water temperature can not be maintained at 28 C, and the temperature of the water radually decreased with time, which affects the feedin of tilapia. 4. Conclusion Micro-electrolysis can effectively remove the ammonia in aquaculture water, but at the same time will cause a short-term increase in the concentration of nitrite. In addition, durin the electrolysis process, the ORP of aquaculture water fluctuated in small amplitude, but it did not affect the fish. The residual chlorine concentration in water radually decreased with the prolonation of the culture time, and the ph value decreased with the prolonation of the electrolysis time, which needed to reularly adjust. The microelectrolysis did not affect the feedin and rowth of fish. Reference Den S., i D., Yan X., Xin W., i J., Zhan Q., 216, Bioloical denitrification process based on the Fe () carbon micro-electrolysis for simultaneous ammonia and nitrate removal from low oranic carbon water under a microaerobic condition. Bioresource Technoloy, 219, Han Y., i H., iu M., San Y., ian C., Chen J., 216, Purification treatment of dyes wastewater with a novel micro-electrolysis reactor. Separation and Purification Technoloy, 17, iu., iu Y.H., Wan.N., i T., Cai H.Y., 215, Preparation of iron carbon micro-electrolysis materials and research on its continuous treatment process of actual wastewater, Ind. Water. Treat, 35, 6. Qi Y., He S., Wu S., Dai B., Hu C., 215, Utilization of micro-electrolysis, up-flow anaerobic slude bed, anoxicoxic-activated slude process, and bioloical aerated filter in penicillin G wastewater treatment. Desalination and Water Treatment, 55, 6, Wei X., i D., i J., Hu Q., Den S., 216, Nitrate removal and microbial analysis by combined microelectrolysis and autotrophic denitrification. Bioresource technoloy, 211, Xu X., Chen Y., Zhan T., Ji F., Xu X., 216, Treatment of pharmaceutical wastewater usin interior microelectrolysisfenton oxidation-coaulation and bioloical deradation. Chemosphere, 152, Zhan Q., 215, Treatment of oilfield produced water usin FeC micro-electrolysis assisted by zero-valent copper and zero-valent aluminium. Environmental technoloy, 36(4),