| Utilization of steel slag made artificial algal reef to construct artificial algal field will be international central issue to rebuild damaged marine ecology system and solve the seawater eutrophication. This technology originated from Japan and have been used in certain closed bays with serious pollution. This technology have not be introduce to our country. At present, this technology place extra emphasis on steel slag's certain feature, such as porous, stable, rich of nutrient element, while ignore the possibility of utilizing steel slag to get rid of nitrogen and phosphorus in the eutrophic seawater, the influence about the quality of the seawater and alga with steel slag are also absent. This paper take steel slag from Qingdao steelwork and Gracilaria lemaneiformis as experimental materials, focus on the treatment effects of eutrophic seawater with steel slag, Gracilaria lemaneiformis and steel slag-Gracilaria lemaneiformis, in addition, this paper study the influence about the quality of the seawater and alga with steel slag, investigated the possibility of utilizing steel slag as artificial algal reef material.This paper research the removal rate of nitrogen and phosphorus in the eutrophic seawater with steel slag. And experiment results show that most of phosphorus in the eutrophic seawater was removed by steel slag. When the concentration of phosphorus was 0.20mg/L, the added steel slag's density was 10g/L, granularity was smaller than 80 grids,97.91% of phosphorus were removed. When the concentration of phosphorus<0.20mg/L, the added steel slag's density was lOg/L, granularity was smaller than 80 grids, the removal rate of phosphorus with steel slag rise while the concentration of phosphorus in the seawater rise. But steel slag will dissolve nitrogen out to the seawater, so steel slag has no use on removing nitrogen of eutrophic seawater.This paper research the removal rate of nitrogen and phosphorus in the eutrophic seawater with Gracilaria lemaneiformis. Experiment results show that, when the concentration of nitrogen was 1.20mg/L, concentration of phosphorus was 0.20mg/L, the Gracilaria lemaneiformis with the initial density of 3g/L has highest removal rate of nitrogen and phosphorus. Utilization of Gracilaria lemaneiformis with the initial density of 3g/L to treat eutrophic seawater (concentration of nitrogen was 0.3～4.8mg/L, concentration of phosphorus was 0.05-0.8mg/L), the removal rate of nitrogen and phosphorus in the eutrophic seawater with Gracilaria lemaneiformis fall after rise while the concentration of nitrogen and phosphorus rise in the eutrophic seawater. When the concentration of nitrogen was 4.8mg/L, concentration of phosphorus was 0.8mg/L, the removal rate of nitrogen and phosphorus with Gracilaria lemaneiformis was 67.38% and 40.42%, and Gracilaria lemaneiformis grow badly.In order to combine the advantages of steel slag and Gracilaria lemaneiformis about treated eutrophic seawater, the two materials are composed of "steel slag-Gracilaria lemaneiformis" system in certain ratio, and the systems are used to treat eutrophic seawater. Result show that:when the added steel slag was lOg/L, the initiatory density of Gracilaria lemaneiformis was 2g/L,77% of nitrogen and 99% of phosphorus were removed. The concentrations of nitrogen in the cheated seawater was 0.268mg/L, better than level two seawater standard; The concentrations of phosphorus was 0.002mg/L, better than level one seawater standard. Steel slag will not affect the quality of seawater and the growth of Gracilaria lemaneiformis when the content of steel slag≤10g/L.Steel slag physical adsorption and chemical precipitation of phosphorus, Gracilaria lemaneiformis biological uptake of phosphorus and nitrogen are combined in "steel slag-Gracilaria lemaneiformis" system, so the system can obviously reduce the concentrations of nitrogen and phosphorus of eutrophic seawater. Utilization of "steel slag-Gracilaria lemaneiformis" system to treat eutrophic seawater was firstly proposed by this paper, this technology not only solve the difficult problem of handle steel slag, but also solve the problem of eutrophic, promote the sustainable development of steel industry. |
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