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Open AccessArticle

Purification of Forest Clear-Cut Runoff Water Using Biochar: A Meso-Scale Laboratory Column Experiment

1
School of Forest Sciences, University of Eastern Finland, Yliopistokatu 7, FI-80101 Joensuu, Finland
2
Department of Environmental and Biological Sciences, University of Eastern Finland, Yliopistonranta 1 E, FI-70210 Kuopio, Finland
3
Department of Forest Sciences, University of Helsinki, Latokartanonkaari 7, FI-00014 Helsinki, Finland
*
Author to whom correspondence should be addressed.
Water 2020, 12(2), 478; https://doi.org/10.3390/w12020478
Received: 16 December 2019 / Revised: 22 January 2020 / Accepted: 6 February 2020 / Published: 11 February 2020
(This article belongs to the Section Water and Wastewater Treatment)
Biochar can be an effective sorbent material for removal of nutrients from water due to its high specific surface area, porous structure, and high cation and anion exchange capacity. The aim of this study was to test a biochar reactor and to evaluate its efficiency in runoff water purification and consecutive nutrient recycling in clear-cut peatland forests. The goodness of the method was tested in a meso-scale (water volume thousands of liters) reactor experiment by circulating runoff water through wood biochar-filled columns and by determining water nutrient concentrations in the column inlet and outlet. The pseudo-first and second order kinetic models were fitted to the experimental data and the adsorption rate (Kad) and maximum adsorption capacity (Qmax) of the biochar reactor were quantified. The concentration of total nitrogen (TN) decreased by 58% during the 8-week experiment; the majority of TN adsorption occurred within the first 3 days. In addition, NO3-N and NH4-N concentrations decreased below the detection limit in 5 days after the beginning of the experiment. The maximum adsorption capacity of the biochar reactor varied between 0.03–0.04 mg g−1 biochar for NH4-N, and was equal to 0.02 mg g−1 biochar for TN. The results demonstrated that the biochar reactor was not able to adsorb TN when the water TN concentration was below 0.4 mg L−1. These results suggest that a biochar reactor can be a useful and effective method for runoff water purification in clear-cut forests and further development and testing is warranted. Unlike traditional water protection methods in peatland forestry, the biochar reactor can effectively remove NO3-N from water. This makes the biochar reactor a promising water protection tool to be tested in sites where there is the risk of a high rate of nutrient export after forest harvesting or drainage.
Keywords: adsorption; biochar reactor; column experiment; inorganic nitrogen; total nitrogen adsorption; biochar reactor; column experiment; inorganic nitrogen; total nitrogen
MDPI and ACS Style

Kakaei Lafdani, E.; Saarela, T.; Laurén, A.; Pumpanen, J.; Palviainen, M. Purification of Forest Clear-Cut Runoff Water Using Biochar: A Meso-Scale Laboratory Column Experiment. Water 2020, 12, 478.

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