Study On Mechanism Of Floating Plants Purifying Iron-polluted River Water

In order to solve the problem of iron-polluted acid pickling ent ering polluted river water due to the imperfect construction of sewa ge pipe network system in Longwan,Wenzhou.The purification effect of floating plants on iron-polluted river water is studied.The effect s of initial Fe²⁺concentration,biomass and initial pH on the purific ation effect of floating plants are investigated,and the mechanism o f floating plants purifying iron-polluted river water was discussed.T he main conclusions are as follows:（1）Myriophyllum verticillatum,Hydrocotyle verticillata,Hygroryza aristata,Ludwigia peploides Kaven subsp.Stipulacea Raven,Pistiastra tiotesL,Rotala Rotundifolia Koehne,six different floating plants have different purification ability for iron-polluted water.The order of p urification ability of Fe²⁺is Hygroryza aristata>Hydrocotyle verticilla ta>PistiastratiotesL>LudwigiapeploidesKavensubspStipulaceaRaven>My riophyllum verticillatum>Rotala Rotundifolia Koehne,the removal rat es are 96.74%,96.71%,96.59%,87.36%,85.18%and 84.42%;the o rder of purification ability of total iron is Hygroryza aristata>Pistia stratiotesL>Hydrocotyleverticillata>Myriophyllum verticillatum>Ludwig ia peploides Kaven subsp.Stipulacea Raven>Rotala Rotundifolia Koe hne,the removal rate is 90.66%,88.73%,87.04%,82.91%,79.25%and 71.10%.Among them,Hygroryza aristata has strong tolerance to iron-polluted water and the best purification effect.The removal rate of total iron is as high as 90.62%,which has significant adva ntages compared with other floating plants.（2）When Fe²⁺is between 1.0 mg/L and 10.0 mg/L,the remov al rate of iron-polluted water increases firstly,then decreases.The tre atment effect is the best at 5.0 mg/L,and the total iron concentrati on in water decreases to 0.453 mg/L.When the concentration of Fe²⁺is 5.0 mg/L and the biomass is 200 g-500 g,the variation trend of Fe²⁺concentration and total iron concentration in water is similar.After 72 hours,when the biomass is 350 g,the concentration of i ron ion in water decreases to 0.22 mg/L;The optimum pH for the purification of iron-polluted water by Hygroryza aristata is 5-8.U nder the condition,the removal rate of Fe²⁺and total iron are 95.43%-98.41%and 92.29%-94.57%,respectively.Intermittent repeated a eration and continuous aeration can promote the purification of iron-polluted water,but the treatment of continuous aeration is better.A fter 24 h,the removal rate of water iron pollution by continuous a eration is 94.6%.（3）The mechanism by which Hygroryza aristata purifies iron-p olluted water is plant accumulation,followed by sedimentation.The accumulation of iron increased with the increase of iron concentrat ion.The accumulation of iron at different concentrations are 176.739 mg·kg^-1,419.198mg·kg^-1,1288.277 mg·kg^-1,1358.888 mg·kg^-1,144.8038 mg·kg^-1.（4）Under different phosphorus concentrations,the iron plaque quality of roots is not much different.However,when the phosphor us concentration is 1.0 mg/L,the phosphorus enrichment of iron pla que is as high as 2268 mg·kg^-1,which is much higher than 789 m g·kg^-11 when the phosphorus concentration is 2.5 mg/L.（5）Under dynamic simulation of iron-polluted river,using Hyg roryza aristata and aeration treatment can achieve optimal purificati on effect on iron-contaminated water.The effluent total iron concentr ation is reduced to 0.5 mg/L after 24 h.