Evaluating the influence of pH adjustment on chemical purification efficiency and the suitability of industrial by-products as alkaline agents

Journal of Environmental Management
Elisangela Heiderscheidt, Tiina Leiviskä

Abstract

Metal salts of iron are currently used in several treatment facilities purifying peat extraction runoff water. Although chemical purification is considered best available technology for the treatment of this natural humic water, fluctuations in purification efficiency occur with low pH (3-4) and high metal concentration found in treated waters. The need for pH neutralisation increases the costs and overall environmental impacts related to chemical purification. The use of industrial by-products can decrease costs while supporting the sustainable use of natural resources and the principle of a circular economy. This study investigated the suitability of a range of calcium-based alkaline products (including by-products of the paper, cement and mineral industries) for neutralisation of chemically treated runoff water. The influence of the time of pH adjustment relative to time of coagulant addition (before coagulant, after but within coagulation, during flocculation and after sedimentation) on purification efficiency was evaluated. The hypotheses that the physical form of the coagulant was a relevant factor affecting purification was also assessed. The best performing pH-adjusting products were cement kiln dust (CaO and SiO2) and ...Continue Reading

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