RESUMEN
This study investigated an alternative carbon source derived from maize cobs (MCs) to enhance nitrogen removal in saline constructed wetlands (SCWs). The main objectives were to select the proper pretreatment method of MCs for rapid carbon release; and to investigate the effects of maize cob pieces (i.e. MCP) and three addition levels of maize cob lixiviums (i.e. L-MCL, M-MCL and H-MCL) on nitrogen purification performance and microbial characteristics of SCWs. Results showed NaOH pretreatment enhanced carbon release of MCs in seawater (from 7.5 ± 0.4 mgCOD g-1 to 16.4 ± 0.2 mgCOD g-1). The 80-d trial showed SCWs with M-MCL addition performed well on nitrogen removal: NO3-N, 88.8 ± 11.6%; NO2-N, 91.1 ± 3.5%; TAN, 96.5 ± 1.6%; TIN, 89.8 ± 10.4%; with 2 mg L-1 effluent COD. Denitrification parameters confirmed MCL to be a high quality carbon source: denitrification potential (PDN) = 0.16 gN gCOD-1; heterotrophy anoxic yield coefficient (YH) = 0.54 gCOD gCOD-1. The MCP and H-MCL treatments improved substrate dehydrogenase activity, indicating a higher microbial activity in these SCWs. Sequencing analysis revealed that, regardless of addition manners, carbon sources from MCs changed the rhizosphere microbial community. At genus level, Anaerophaga (10.1%), Granulosicoccus (8.2%) and Sulfurimonas (6.6%) dominated in SCWs under MCP treatment. Increased MCL addition levels improved the relative abundance of Vibrio, Malonomonas and Caldithrix, suggesting the enhancement of denitrification. Relative high proportions of Desulfotignum and Desulfovibrio, and Sulfurimonas were observed in MCP and H-MCL SCWs, implying that sulfate reduction occurred in SCWs with excess carbon sources.
Asunto(s)
Nitrógeno/aislamiento & purificación , Eliminación de Residuos Líquidos/métodos , Humedales , Zea mays/química , Acuicultura , Bacterias/genética , Carbono , Desnitrificación , Procesos Heterotróficos , Microbiota/genética , Rizosfera , Agua de MarRESUMEN
Chicken manure substrate (fermented chicken manure:fermented corn stalk:river sand=3:4:3) and cattle manure substrate (fermented cattle manure:fermented corn stalk:river sand=3:4:3) were used to study the effects of microbial agents ('Difulai', enzyme microorganism, EM bacteria, Bacillus subtilis, and agricultural microbial agent) on substrate enzyme activities and tomato yield and quality. The results showed that the activities of urease, invertase and alkaline phosphatase in both two substrates all significantly increased at 40 d and 60 d after microbial agent addition. The growth, yield and vitamin C content of tomato were higher than those of control. Among the microbial agents, 'Difulai' showed the best effect in both two substrates. Plant yield increased by 14.7% and 40.0%, tomato vitamin C content increased by 22.2% and 39.7% respectively in chicken manure and cattle manure substrate with 'Difulai' addition. Yield and vitamin C content of tomato plant in chicken manure substrate without microbial agent addition were higher than that in cattle manure substrate, while there was no significant difference in two substrates with 'Difulai' addition.