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Investigation of blast furnace slag as a filter media for phosphorus removal in small wastewater treatment plants
2003 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Swedish environmental legislation promotes reduction of nutrient supply to water bodies and reuse of nutrients found in wastewater. Therefore, in small wastewater treatment units, phosphorus entrapment may be done a filter consisting of phosphorus sorption material. Thereafter, the filter material may be used in agriculture. As different kinds of slags are known to have high sorption capacity and they come into existence in large amounts, they are an attractive alternative. In this Master’s Thesis the capacity of blast furnace slags to retain phosphorus was studied in different conditions. Moreover, the possibility to utilise used blast furnace slag filter as soil conditioner was evaluated. Within this thesis, a literature study was done and experiments in laboratory and pilot scale were conducted. Blast furnace slag material used was received from SSAB Tunnplåt AB in Luleå. The effluent used in the experiment was either artificial phosphorus solution or wastewater collected from Uddebo Wastewater Treatment Plant in Luleå, and it was primarily treated in step screen. Contact time of 2-4 is needed for phosphorus retention to take place by blast furnace slag regardless of the type of effluent. With bigger contact times no greater retention is expected to occur. The type of effluent, initial phosphorus concentrations and the preparation of filter material of blast furnace slag have an effect on phosphorus sorption capacity of blast furnace slag. Applying wastewater, using a solution of low initial phosphorus content and washing of slag material resulted in lower sorption capacity. Therefore, it is questionable to apply data from experiments done with artificial phosphorus solution in real wastewater applications. Lower than room temperature did not seem to affect greatly on sorption capacity. However, the saturation conditions of slag filter had an indirect influence on the sorption capacity of blast furnace slag. Waterlogged conditions may have extended the age of filter and thus contributed higher sorption capacity. Phosphorus sorption capacity of blast furnace slag filter may be at least 100-200 mg/kg slag when using wastewater effluent. Blast furnace slag is inexpensive by-product from iron-making industry and comes into existence in large amounts. Moreover, the material seems to have a higher capacity to retain phosphorus from wastewater than many other filter materials. Thus, it may be potential substrate for wastewater applications. However, before it can successfully utilised in wastewater applications, further studies of functionality need to done in full scale. Moreover, the effect of blast furnace slags in wastewater applications on recipient and sorption of heavy metals need to be studied further. Utilisation of used blast furnace slag from wastewater application in agriculture may have a positive effect in different ways. Conditions in soil for plant growth are promoted by improvement of soil structure, increase of soil pH and release of desired compounds. However, the leaching of heavy metals from blast furnace slag needs to be studied in situ prior to utilisation in agriculture can occur.

Place, publisher, year, edition, pages
Keyword [en]
Technology, avloppsbehandling, filter, slagg, sorption, fosfor
Keyword [sv]
URN: urn:nbn:se:ltu:diva-42153ISRN: LTU-EX--03/215--SELocal ID: 035c5ee2-3aa2-4a26-876b-2f285ef02c0fOAI: diva2:1015370
Subject / course
Student thesis, at least 30 credits
Educational program
Environmental Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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