Study Of Biochemical Monitoring By Iron And Calciumcarbonate In Integrated Constructed Wetland

Integrated constructed wetland is a kind of ecological wastewater treatment with high contaminants removal efficiency.There are many contaminants removal mechanism in this ecosystem.Nitrogen removal mainly depends on nitrification-denitrification mechanism,and phosphorus removal mainly depends on the adsorption and biological phosphorus removal.Iron – calcium-carbonate affected the physical,chemical and biological mechanisms in ecosystem.The content of carbon and oxygen in system affected the performance of contaminants removal in ecosystem operation.It is necessary to study carbon and oxygen supplement for improvement of contaminants removal in wastewater treatments.In this study,a new integrated ecological wastewater treatment was designed and built.There were two different type of this new integrated treatments,half-vertical subsurface flow constructed wetlands(H-CW)and shallow algal pond-vertical subsurface flow constructed wetlands(AP-CW).Improved performance and purifying mechanism of integrated treatments were confirmed during the whole year operation.Iron and calcium-carbonate as growth adjuster were added in integrated treatments,and the effect of adjuster on contaminants removal performance and manipulation of bio-physicochemical mechanism were researched as well.The optimal dosage of adjuster in algaebacteria system in algal pond was studied.The contaminants removal performance with different initiate phosphorus source and N/Ps under different seasons in integrated treatments was confirmed as well as the influence of adjuster on contaminants removal improvement and bio-physicochemical control.The results as follow:(1)The variation of physicochemical indices,algae biomass,contaminants removal performance,bacteria communities were certain with iron and calcium-carbonate added in influent.Optimal dosage of iron and calcium-carbonate(10000 nmol/L Fe3+,5000 nmol/L iron and 0.2 mg/L calciumcarbonate powder)and iron utilization was confirmed as well.This result was proved by microbial community analysis,variation of bacteria amounts and activity of microbial.TN,TP and BOD5 VI removal was 99.98 %,77.71 % and 91 %,respectively in system,which can continuous operated for 20 days.It is positive for algae growth by using iron and calcium-carbonate.Algae biomass will increase because of adding calcium-carbonate,which hydrolyzed HCO3-prioritized to algae absorption.Iron had been supplied as microelements and iron limitation was overcame.As a result,algae biomass was increased.(2)The improved performance of contaminants removal in integrated treatments with simulated surface water was proved and the removal mechanism of nitrogen and phosphorous was discussed as well.As a result,the performance of contaminants improved significantly causing by algae,which not only absorb nitrogen and phosphorous as growing nutrients but also release oxygen for supplement of subsequent operation.Except that,dead algae can be decomposed in treatments and worked as microbial carbon source supplement.(3)The variation and supplement of carbon source in integrated treatments with different dosage of iron at different seasons were studied.AP-CW treatment was the optimal ecological integrated treatment with 10 times iron dosage as mentioned in(1)about 5.6 mg/ L Fe3+,2.8 mg /L iron powder and 0.2 mg/L Ca CO3 powder.Under the condition of dynamic balance,30 mg/L COD was increased,and after 1 day operation in treatment,nitrogen was removal completely.There is a negative relationship between concentration of COD and Fe2+ ion.Comparing to other traditional carbon source,dead algae as microbial carbon source was favor to nitrogen removal in denitrification by analysis of microbial communities though high throughput pyrosequencing.(4)The performance of nitrogen and phosphorous removal was influenced by some factors,which affected the variation and working mechanism in bio-physicochemical areas.After research and discussion,the optimal condition was confirmed,initiate phosphorous source was PO43-and N/Ps was 30 in influent at 3-day HRT with 92.85 % TN removal and 69.74 % TP removal.The removal performance by using PO43-and PO3-were similar.The DOP removal performance was obviously improved by using P2O7-.(5)Under different dosage of iron,different N/Ps,different initiate phosphorous,different seasons in different integrated treatments,the contaminants removal performance were studied.Optimal dosage of iron,influent condition and improved performance of contaminants removal were confirmed.AP-CW treatment was the optimal ecological wastewater treatment with low C/N in influent.Optimal condition was PO43-as initiate phosphorous source,N/Ps 30 and suitable adjuster(5.6 mg/L Fe3+,2.8 mg/L iron powder and 0.2 mg/L Ca CO3 powder)in influent.This results was proved by analysis of microbial communities though high throughput pyrosequencing as well.The optimal iron dosage was 10 times,and the optimal ecosystem treatment was ACW10.After oneoffs added of adjuster by adding wastewater with PO43-as initiate phosphorous source,N/Ps 30 in algal pond combined with constructed wetlands,5 repeated treatments was continuous operation with 80.6 % TN removal,57.3 % TP removal and 0.042 mg/L iron concentration in 5th effluent.Above all,we studied the algae operated mechanism and growth in algal pond.A new algal pond combined with constructed wetlands system was designed for wastewater treatment.Iron – carbon transferring mechanism and the removal of nitrogen and phosphorus were studied.Meanwhile,we confirmed the influence of iron and calcium-carbonate as growing adjuster for nitrogen and phosphorus removal in integrated treatments as well.