Esko Lakso

Contribution of cation exchange property of overflow wetland peat to removal of NH4+ discharged from some Finnish peat mines

Abstract The importance of adsorption on peat for decreasing NH 4 + was estimated in four overland flow areas (OFA) in northern Finland, where peat mining water is purified by conducting it across a natural mire of a given size. The effective cation exchange capacity (ECEC) values of peat in the OFAs ranged from 21.4 to 92.7 meq per 100g, being generally highest in the surface 0–15 cm. It was estimated that about 4.6–5.8% of the peat cation exchan e sites could be occupied by NH 4 + , corresponding to a NH 4 + retention capacity of about 0.18 to 0.77 g kg −1 dry peat. Assuming that the retention was attributable to the 0–15 cm surface peat layer alone, the calculated NH 4 + retention potential of OFA peat should have lasted under 6 months with the loadings imposed on the OFAs and the decreases in NH 4 + amounts in peat mining water considered here. The actual duration of peat capacity to retain NH 4 + in the OFAs has, however, already been shown in this research to be longer, and apparently will be so also in future, probably as a result of two processes: nitrification and subsequent N loss through denitrification, and biological assimilation. Hence, cation exchange capacity of OFA was an important property that contributed to surface water protection against eutrophication by N.

The Effect of Ozonation on the Size Fractions of Manganese

Manganese is a commonly found substance in groundwater in Finland. As a powerful oxidant, ozone can be used for the oxidizing of manganese even without raising the pH. The SFS (Finnish Standards Association) standard has set the accepted limit for soluble manganese to 0.45 μm. However, some research papers have used the limit of 30 kD (kilodalton) for soluble manganese. This research concentrates on the size fractions of manganese in four samples of untreated groundwater and in four samples of ozonized groundwater when treated with 0.45 μm, 0.20 μm, 100 kD, 30 kD, and 10 kD filters. In all tests, nearly all manganese contained in raw water penetrated all filters. There were slight variations in the flocculation of manganese in ozonized groundwater; nevertheless, hardly any reduction in manganese levels took place beyond 100 kD. After ozonation, there were two water samples which surpassed the manganese limit of 50 μgl−1 set for domestic water when the filtration was 0.20 μm and another two samples when the filtration was 100 kD.

The effect of ozonation on the size fractions of iron and total organic carbon in groundwater.

This paper deals with the size fractions of iron and organic matter in four samples of untreated (raw) and ozonized humus-containing groundwater. The fractionation was made to specify the needed pore size of possible membranes for the removal of oxidated iron and organic material. In the tests, iron contained in two of the raw water samples penetrated all filters almost completely. The iron in ozonized water flocculated somewhat differently in different types of water. In three water samples, the set limit for domestic water was reached after filtration with a 0.20 μ m filter, which was done after ozonation had flocculated the iron. One water sample required a 100 kD filtration.