The SULKA (New and innovative methods of water purification to reduce loading from peat extraction)

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Elisangela Heiderscheidt
added a research item
Chemical treatment is considered best available technology for purification of peat extraction runoff in Finland, due to its capability to remove dissolved organic carbon (DOC), suspended solids and nutrients. However, lack of optimisation and adaptation of this method for purification of diffuse pollution sources, e.g., peat extraction runoff, has led to significant fluctuations in purification efficiency. This thesis evaluated the suitability of commercially available coagulants for the treatment of typically humic water. Inorganic (ferric sulphate, aluminium sulphate and a mixed product) and organic (polyDADMAC, polyamine, chitosan and tannin products) coagulants were studied. Investigations included assessment of required dosage and the influence of process parameters (pollutant concentration, mixing, water pH and temperature) on coagulant performance. In addition, the process conditions in existing treatment systems were examined in field experiments aimed at identifying possible factors affecting purification. Ferric sulphate (FS) was the most effective of the coagulants tested. It produced excellent flocs and achieved higher removal efficiency, particularly for DOC, than the other coagulants. However, the dosage required for FS was significantly higher than for e.g., polyDADMAC and chitosan. Moreover, samples treated with FS displayed high iron concentration and acidic pH. The organic polymers achieved satisfactory results, but further research is needed before they can become viable alternatives to metal salts. The quality of peat extraction runoff water was found to vary significantly. It was also observed that variations in DOC concentration, even for particulate rich samples, controlled coagulant dosage and, consequently, treatment efficiency. For inorganic coagulants, mixing provided during flocculation had a more significant influence on purification than mixing provided during coagulation. This is relevant hence in now existing treatment facilities no mixing is employed during flocculation. Based on the research conducted, suggestions were formulated for process optimisation aimed at reducing variations in purification efficiency, thus increasing the reliability of the method and reducing related environmental impacts.
Elisangela Heiderscheidt
added a research item
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 Mahtikalkki (Ca(OH)2, CaCO3 and CaO), by-products of the cement and paper industry, respectively. Time of pH adjustment in relation to time of coagulation addition had a significant influence on purification efficiency, especially when solid coagulant was used. Adjustment of pH at 30 s before coagulant dosing resulted in a negative effect on treatment results. Based on results obtained, suitable points of pH adjustment are during the flocculation stage or at the outlet of sedimentation, particularly if solid coagulants are used. Full text available:
Elisangela Heiderscheidt
added an update
Greetings mining industry experts!
Interreg Nord-funded Min-North and RESEM projects will host a joint seminar on the 21st of September 2017 at the University of Oulu, Finland.
We would like to invite you to attend the seminar which will focus, generally on environmental impacts of mining activities and the responsibility of different stakeholder on achieving sustainability and more specifically, on the topics of the hosting projects which are:
- Development, evaluation and optimization of measures to reduce the impact on the environment from mining activities (Min-North)
- How remote sensing can be used on monitoring of mines (RESEM)
During the seminar, key results from both projects will be presented from all partners institutions (from Finland, Sweden and Norway) and discussed together with the invited key note speakers from mining industry, environmental authorities and other stakeholder groups.
The detailed (preliminary) seminar program can be found as an attachment. Please note that there are no fees for seminar registration and attendance.
You can register to the seminar using the provided link. Please register the latest by 12.9.2017:
On behalf of Min-North and RESEM project teams,
We warmly welcome you to the seminar!
Elisangela Heiderscheidt
added 2 research items
Peat extraction runoff water requires chemical treatment to remove organic matter and phosphorus. In Finland, ferric sulphate (FS) is normally used as coagulant agent, but significant variations in runoff water quality and the lack of optimisation of process parameters has led to increased acidity, metal and sulphate concentrations in the purified water. The use of synthetic organic polymers as an alternative to the commonly applied metal salt coagulant is suggested to better cope with typical variations in runoff water quality. This study evaluated the suitability of two synthetic organic polymers (polyDADMAC and polyAmine) for the purification of humic and sediment-rich diffuse runoff by comparing their performance to the normally applied iron-based coagulant. FS was found to require up to fourfold higher dosages but achieved higher overall purification levels than the organic polymers. In particular, removal of organic matter was substantially higher when FS was used. Of the two synthetic organic products, polyDADMAC achieved slightly better purification rates and required lower effective dosages than polyAmine. Low water temperature (2°C) had a detrimental effect on the performance of all coagulants, especially regarding removal of suspended solids. Decreasing the initial water pH (6.5–4.5) resulted in a substantial decrease in the coagulant dosages required to achieve acceptable purification levels. Although FS presented higher overall removal efficiency, the synthetic organic polymers performed satisfactorily and can potentially replace metal salts as primary coagulants in the treatment of humic and sediment-rich water.