Strontium-containing Wastewater Treatment By A Mixing Prilling-microfiltration Combination Process

This paper investigated the treatment of strontium-containing wastewater by themixing prilling process with a lab-scale device in order to solve the problems that themembrane fouling was serious and the sludge was difficult to discharge inprecipitation–microfiltration combination process for strontium removal. Thestrontium element was removed by forming compacted crystal particles withimproved sedimentation performance when sodium carbonate and calcium carbonatewere used as precipitating agent and crystal seed, respectively. The effluent turbiditywas reduced so that the load of following microfiltration process was alleviated.On the basis of the above tests, a submerged microfiltration membrane modulewas added after the mixing prilling method to investigate the strontium-containingwastewater treatment effect by the mixing prilling-microfiltration combinationprocess with a lab-scale device. In the tests, sodium carbonate was still used asprecipitating agent. In order to improve the settling effect, flocculant ferric chloridewas dosed in the membrane separator.The method of preparing the crystal seeds was investigated first. The resultsshowed that the effluent turbidity and hardness were stable and the formed crystalparticles were compacted after30prilling cycles. The growth rate of the crystalparticles was faster when the crystal seeds were prepared using the strontium-containing water. When the strontium concentration of influent was approximate5.0mg/L, the crystal seeds were prepared using the non-strontium-containing water andthe water in which the concentration of strontium was5.0mg/L, the mean DFs were165and279, and the mean CFs were2.09×10~3and3.17×10~3, respectively. Both ofthe CF and the DF were higher when the strontium-containing water was used toprepare the crystal seeds. So we chose the raw water to prepare the crystal seeds.Secondly, the strontium-containing wastewater treatment effect was investigatedby the mixing prilling-microfiltration combination process when the temperature wassame and the strontium concentration of the raw water or the dose of ferric chloridewas different. The results showed that when the mean temperature was about21℃,the dose of ferric chloride was10mg/L and the strontium concentration of influentwere5.0mg/L and12.0mg/L, the mean DFs were279and561, and the mean CFswere3.17×10~3and2.86×10~3, respectively. The DF was improved with the increasedstrontium concentration of influent. When the mean temperature was about27℃, the strontium concentration of influent was about5.5mg/L, and the doses of ferricchloride were20mg/L and10mg/L, the mean DFs were525and484, and the meanCFs were1.65×10~3and2.12×10~3, respectively. The DF was improved with theincreased dose of ferric chloride, but the CF was reduced.