Abstract: A comparison study was carried out on effects of mixing-immobilization(MI) and stratifying-immobilization(SI) of algae and bacteria removing nitrogen and phosphorus from aquacultural wastewater and influence of light intensity and temperature on the effects.Stratifying-immobilization was done in two forms,SI1and SI2.The former had algae in the outer layer and bacteria in the inner one,whereas the latter did reversely.Results show that under given conditions for 72 h,MI and SI2 removed 91.20% and 90.77%,respectively,of the nitrogen in the wastewater,while SI1 did only 60.4%.However,MI and SI1 were much better in removing phosphorus than SI2,MI and SI1 was 90.31% and 84.78%,respectively,in phosphorus removal rate,whereas SI2 was only 32.09%.When light intensity was set at <6 000 lx,the nitrogen removal rate of SI2 was over 88%,much higher than that of MI and SI1(80%);and when light intensity was high enough(>6 000 lx),the nitrogen removal rates of both SI2 or MI were over 89%,higher than that of SI1.The optimal temperature for nitrogen and phosphorus removal was 20～30 ℃ in all the three treatments,MI,SI1 and SI2.

Key words: mixing-immobilization, stratifying-immobilization, algae-bacteria immobilization, aquaculture wastewater, nitrogen, phosphorus, removal rate