Study On Ammonia Treatment For Aquaculture Wastewater

The industry of aquaculture has been developing rapidly in recently. Great deal of aquaculture waste water was produced and entered the environment with bad effects such as entrophication and red tide. The balance of zoology and diversity of creatures were also destroyed, which lead to economical loss. Ammonia is the most important contamination of aquaculture waste water and it is very difficult to remove from the water. There are rare special technologies of method for aquaculture waste water treatment. For the sea water system, it is more difficult because of the high salinity and complexion of the composition. Physical method such as foam separation and filtration are popular methods for aquaculture waste water treatment. These methods can remove suspended particles effectively but can not reduce the concentration of solvable matters, including ammonia.In this study, several method were set to treat aquaculture waste water. Experiments were designed for fresh water and seawater separately. Ammonia removal rate of all the methods and the characters of the course were noted. Appropriate methods were selected according to the treatment result and the aim concentration. After this period, the routine of water treatment craftwork were designed. Cost and benefit were calculated cursorily. All the result refers significative data for further study of aquaculture wastewater treatment. The main results were summarized as follows:1. The results of ammonia removal of different methods in freshwater system were examined and craftwork with effective methods were set up.(1)Immobilized sludge in fluidized bed has a good ability to remove ammonia from aquaculture wastewater and its result was better than normal sludge. Experiment was designed to improve the properties of immobilized beads. The result showed that the best composition of immobilization reagent was: PVA80g/L,Sodium alga acid 4g/L,activated coal10 g/L,SiO28g/L,CaCO30.5g/L。The value of Sludge/Reagent is 1:4 (w/w),and the best diameter for beads was 3mm。When used to treat aquaculture wastewater, the best condition for work was: with beads delivery 150 g/L, resident time4-8h是,temperature 25-30℃,pH 7-9.(2)Spiralina depended on ammonia as necessary nutrient for growth after the process of domestication culture. High concentration ammonia has a toxic effect on Spiralina. The higher the concentration, the stronger the effect is. The appropriate ammonia range is below 50mg/L. The best working condition of Spiralina for ammonia removal is pH6-11,temperature 25-40℃, algae delivery amount 91×104个/mL。(3)The ammonia concentration of real aquaculture wastewater treated only by immobilized sludge can reach China discharge water quality Standard. When resident time is 5h, ammonia concentration can reach Class 2 standard(below 25mg/L),and treatment cost was 0.547yuan/ m3. When resident time is 6h, ammonia concentration can reach Class 1 standard(below 15mg/L), and treatment cost was 0.656yuan/ m3. To satisfy the quality requirement for aquaculture reuse, further treatment was needed. After treated by Spiralina for 8h, ammonia concentration is below 0.5mg/L and non-ioned ammonia is no more than 0.02mg. The water could be reused for aquaculture.2. By raising the seawater ratio in the water gradually, sludge and Spiralina at last got used to the seawater system. he results of ammonia removal of different methods in freshwater system were examined and craftwork with effective methods were set up.(1)Sludge got used to mariculture system by raising seawater ratio gradually. And the result showed that it can also reduce the ammonia concentration in mariculture wastewater. The best condition for use is: temperature25-35℃,pH7-9,resident time12-16h。 (2)Ozone was used to remove the ammonia remained after former treatment process. The reaction of Ozone with ammonia was so fast that it ended in 1h. there is a problem that producing ozone cost too much.( 3 ) Chlorella pynenoidos,Synechocoocus sp,Dunallelia salin and Phaeodactylum tricornutum origined from seawater and were selected to treat ammonia in mariculture wastewater after comparison experiment.(4)The ammonia concentration of real aquaculture wastewater treated only by sludge can reach China discharge water quality Standard after a treatment process of 12h. And the treatment cost was 0.713yuan/m3 wastewater. To satisfy the quality requirement for aquaculture reuse, further treatment was needed. After treated by Spiralina for 36h, ammonia concentration could satisfy the requirement for reuse. The algae collected produced a profit of about 0.30yuan/m3 wastewater. Using ozone as a succedent treatment may cost 8.42 yuan/ m3 wastewater.