| At present,the water pollution caused by agricultural source pollution such as livestock and poultry breeding wastewater is serious,but the traditional way of treating aquaculture wastewater by biological method is still insufficient.We proposed a strategy that the water and nutrients in swine wastewater can be utilized for co-culture of plants and algae and the wastewater can be remediated at the time of plant and algal production.In this study,co-culture experiments were carried out to investigate the growth of plants and algae,the purification effect and mechanism by plants and algae in the swine wastewater,and the future application of co-cultivation in wastewater treatment was proposed.The main results are as follows:In the cultivation experiment of sweet potato-Spirogyra communisn-swine wastewater,the biomass in the sweet potato-Spirogyra communisn co-culture treatment was higher than that of sweet potato monocultures with Hoagland nutrient solution and with swine wastewater after one month of cultivation.On the 15th day of the culture period,the plant growth rate in the Dictyosphaerium sp.-Vetiver co-culture was 12.8±1.2（n=3）g FW·D-1,which was significantly higher than that of the Vetiver monoculture with swine wastewater 1.5±1.0（n=3）g FW·D-1,（P<0.01）.The relative growth rate of algae in the co-culture was 0.168 and 0.151（n=3）respectively,and the biomass was significantly higher than that in the algal monoculture with swine wastewater.The results showed that there were significant positive interactions between plants in the swine wastewater culture medium.The co-culture experiment of vetiver and Dictyosphaerium sp.showed that the co-culture could effectively remove the high concentration of ammonia nitrogen and phosphorus in the wastewater and inactivate the various pathogenic bacteria in the wastewater.In the treatments of plant monoculture,algal monoculture and plant-algal co-culture,the time required for NH4+-N to decrease from 102 mg·L-1 to 5 mg·L-1 in wastewater was 65.5 days,34.2 days and 13.3 days,respectively.The time required for TP to decrease from 12.5 mg·L-1 to 2 mg·L-1 was 82.7 days,25.5 days and 16 days,respectively.Pathogens in the plant-algae co-culture treatment were inactivated by supersaturated dissolved oxygen and reactive oxygen species released by algae in the closed containers.In the plant-algae co-culture,35 bacterial genera were detected,among which 31 bacterial operational taxonomic units（OTUs）tended to decrease with culture time.This study analyzed the positive interaction mechanisms between plants and algae in the process of swine wastewater purification via co-culture of plants and algae,and the following main mechanisms were identified:nutrient co-utilization;plant root respiration leading to the acidification of wastewater and the reduction of ammonia toxicity;the consumption of bicarbonate by algae reducing the toxicity of bicarbonate to plants;the oxygen released by algal photosynthesis reducing hypoxia stress and promoting plant growth.Three application modes of using co-culture of plants and algae were constructed to cultivate and purify swine wastewater:ecological hydroponics,plant-algae water purification floating island and plant-algae water purification pond.Ecological hydroponics can be used for modern farm production to obtain plant and algae output.Plant-algae water purification floating island and plant-algae water purification pond are suitable for combined use with other sewage purification technologies.Relevant requirements were putting forward for these application modes,which provided practical reference for the purification of water and resource utilization of the co-culture of plants and algae. |
