Remediation Effect On Oil Pollution From Terrestrial Sources In Artificial Wetland System Of Spartina Alterniflora

Oily wastewater from terrestrial sources not only contains complex petroleum pollutants,but also mixes with inorganic pollutants and heavy metals,etc,it gets increasingly serious harm to offshore area,port and dock environment.Artificial wetland,as one of wastewater treatment methods,has not only low cost,but also good treatment effect,still with ornamental value and adjust the ecological environment.Pollution investigation was conducted in Yongdingxinhe river estuary and offshore area,Beitang,Tianjin.Based on the results,a Spartina alterniflora wetland simulation system was built to study the concentrations changes trend of TPH in surface water&sediment,and analyze the remediation effect on oil pollution from terrestrial sources,and study the TPH abatement from terrestrial sources in Spartina alterniflora wetland in Yongdingxinhe river estuary through monthly monitoring in 2015.The main conclusions were as follows:(1)The surveying results for regional surface seawater in Nov.2015 were:the concentrations of DO were 6.98?8.2 mg/L,an average of 7.4 mg/L;the concentrations of CODMn were 2.78?3.09 mg/L,an average of 2.90 mg/L;the concentrations of inorganic nitrogen were 0.427?0.489 mg/L,an average of 0.458 mg/L;the concentrations of active phosphate were 0.032?0.045 mg/L,an average of 0.039 mg/L;the concentrations of TPH were 0.097?0.148 mg/L,an average of 0.119 mg/L;the concentrations of PAHs were 107.3?159.2 ng/L,an average of 129.7 ng/L,which belong to the inferior forth class of seawater quality standard.Petroleum,inorganic nitrogen and active phosphate were the major pollutants.TPH concentrations in sediments were 551.97?599.29 mg/L,which belong to the second class of marine sediment quality standard.(2)Spartina alterniflora enhanced the adsorption,absorbtion and degradation on TPH in wetland simulation system.After 30 days experiment,the TPH changes in overlying seawater of the experimental groups were:the TPH removal rate of control group was 52.20%,the outlet TPH concentration was 0.190 mg/L;the TPH removal rate of indigenous bacteria group was 84.35%,TPH concentration in the outlet seawater was 0.062 mg/L;the TPH remval rate of Spartina alterniflora-indigenons bacteria group was 87.67%,TPH concentration in the outlet seawater was 0.049 mg/L.The TPH removal rates in surface 10 cm sediment were the TPH removal rate of control group was 10.60%,the TPH removal rate of indigenous bacteria group was 19.75%,the TPH removal rate of Spartina alterniflora-indigenous bacteria group was 25.14%;in intermediate 10 cm sediment,the TPH removal rate of control group was 11.11%,the TPH removal rate of indigenous bacteria group was 19.04%,the TPH removal rate of Spartina alterniflora-indigenous bacteria group was 21.83%;in bottom 10 cm sediment,the TPH removal rate of control group was 10.65%,the TPH removal rate of indigenous bacteria group was 16.66%,the TPH removal rate of Spartina alterniflora-indigenous bacteria group was 19.06%.(3)Biofortification improved purification capacity of TPH in wetland simulation system.The TPH removal efficiency in biological strengthening group was significantly higher than that in non-biological strengthening group.After 30 days,the TPH changes in overlying seawater of the experimental groups were:the TPH removal rate in indigenous bacteria group was 80.13%,the outlet seawater concentration was 0.077 mg/L;the TPH removal rate in indigenous bacteria-dominant bacteria group was 88.00%,the outlet seawater concentration was 0.047 mg/L;the TPH removal rate in Spartina alterniflora-indigenous bacteria group was 81.88%,the outlet seawater concentration was 0.070 mg/L;the TPH removal rate in Spartina alterniflora-indigenous bacteria-dominant bacteria group was 89.16%,the outlet seawater concentration was 0.042 mg/L.The TPH removal rates in the surface 10 cm sediment were the indigenous bacteria group was 10.26%,indigenous bacteria-dominant bacteria group was 13.93%,Spartina alrerniflora-indigenous bacteria group was 12.64%,Spartina alterniflora-indigenous bacteria-dominant bacteria group was 15.09%;in the intermediate 10 cm sediment,indigenous bacteria group was 5.84%,indigenous bacteria-dominant bacteria group was 9.30%,Spartina alterniflora-indigenous bacteria group was 9.26%,Spartina alterniflora-indigenous bacteria-dominant bacteria group was 13.19%;in the bottom 10 cm sediment,indigenous bacteria group was 4.23%,indigenous bacteria-dominant bacteria group was 6.08%,Spartina alterniflora-indigenous bacteria group was 7.71%,Spartina alterniflora-indigenous bacteria-dominant bacteria group was 10.94%.(4)The monitoring results in remediation site showed that the Spartina alterniflora wetland can reduce the flux from the terrestrial pollutants into the sea.From Apr.2015 to Nov.2015,the concentrations of inorganic nitrogen were 0.437?0.650 mg/L,the concentrations of active phosphate were 0.031?0.087 mg/L,the concentrations of TPH were 0.033?0.166 mg/L in Spartina alterniflora wetland adjacent sea.The pollutants distributions in surface seawater were:pier adjacent waters>seaward channel>offshore area,the concentrations of TPH from June to September was significantly lower than that in other month,and the TPH concentrations during flood was less than that during ebb.The concentrations of TPH in September was 0.045 mg/L during flood and 0.034 mg/L during ebb,which was lowest throughout the year.The sediment concentrations of TPH were 505.49?693.79 mg/kg,which was no obvious difference in space and time.