Study On Farmland Low-level Contaminated Water Purification Of Ottelia Acuminate-M.melanioides Wetland In Erhai Basin

In recent years, the buffer zones surrounding Erhai were exploited harderand the pollution load become heavier. Prevention and treatment of farmlandlow-level contaminated water become a difficulty in these regions. Withfarmland pollution is getting worse, the ecosystem was seriously threatenedaround Lake erhai, and the endemic species Ottelia acuminate and Margaryamelanioides have almost disappeared. This research was aimed at discussingthe feasibility of M.melanioides survival in Ottelia acuminate wetlands andeffect of adding M.melanioides in Ottelia acuminate wetlands on waterpurification and pollution degradation of sediments though constructingOttelia acuminate-M.melanioides hydroponics economy wetland, besides,wetland economic benefit was studied either to provide the basis for Otteliaacuminate and M.melanioides restoration and farmland low-levelcontaminated water control. Main results were as follows:(1) Feeding characteristics of M.melanioides on four typical attachedalgae (Navicula.sp, Nitzschia.sp, Planktothrix mougeotii and Scenedesmusquadricauda) of Ottelia acuminate wetland was studied though cultivation. M.melanioides preferred to eat Navicula.sp; When temperature was from20℃to25℃, illumination was between1000lx and2000lx, DO was above3.6mg/Ldid good to M. melanioides’ feeding; The Ingestion Rate had a significantnegative correlation with M. melanioides’ weight (P <0.05), showed a goodexponential relationship with individual wet weight: y=1.620x-1.42, the youngintake algae more than the adults significantly. The investigation results ofOttelia acuminate wetlands showed that there had proper temperature, pH, DO,illumination and adequate Navicula.sp, it’s suitable for M. melanioides’ living,we can build Ottelia acuminate wetland for M. melanioides’ survival andmultiplies.(2) The Ottelia acuminate wetlands whether was added with M.melanioides or not all performed a well purification efficiency on the low-level contaminated water. In HRT7d wetlands, removal ratio of TN,NO3--N, TP reached above50.8%、61.2%,72.4%, respectively, and TN, TPtreatment capacity were above79.9g/(m2·a)、22.8g/(m2·a), respectively; InHRT42d wetlands, removal ratio of TN, NO3--N, TP reached above76.9%、90.9%,87.2%correspondingly, and the TN, TP treatment capacity were above14.1g/(m2·a)、4.6g/(m2·a); Overall, there has little effect on waterpurification when put M. melanioides in.(3) M. melanioides significantly affacted wetland sediment. When M.melanioides existed, the pH was lower, and the Eh was higher. M. melanioidespromoted removal of organic matter, total nitrogen, total phosphorus, it canincrease the amount of microorganisms either.(4) Ottelia acuminate wetlands had a considerable economic benefit, theHRT7d Ottelia acuminate wetland economic benefit can reached10600yuanper mu per year while7900yuan in HRT42d wetlands；When added with M.melanioides wetlands income can be increased at least3200yuan per mu peryear. Ottelia acuminate-M. melanioides wetlands can make benefit more than13000yuan per mu per year.(5) To guarantee the normal growth of Ottelia acuminate, TN, TPconcentration should be controlled above1.02mg/L,0.12mg/L, respectively,in water.Comprehensive consideration of the performance of farmland low-levelcontaminated water purification, degradation of sediment pollution load,normal growth of Ottelia acuminate, and the economic benefit of wetlands,the HRT7d Ottelia acuminate-M. melanioides wetland can be priority inpractical application.