# The Use of Chalcogenite as a Biosorption Bed in the Treatment of Groundwater
## 3 Results
The concentrations of nitrite nitrogen were in the range from 0.008 to 2.35 g N-NO\({}_{2}\)\({}^{-}\)/m\({}^{3}\) and from day 24, exceeded the permissible value of 0.15 g N-NO\({}_{2}\)\({}^{-}\)/m\({}^{3}\). It was only after the 59 th day of the experiment that the content of nitrites decreased, indicating that the nitrification process had been carried out in full. The beginning of the second phase of the nitrification process, characterized by the increase of nitrates in the treated water, occurred after the 51 st day of the experiment (Figure 2). Introduction of the second degree of biofiltration (water II) additionally increased the efficiency of ammonium nitrogen removal, and from day 33 the NH\({}_{4}\)\({}^{+}\) values were on a level from 0 to 0.2 g N-NH\({}_{4}\)\({}^{+}\)/m\({}^{3}\), with a standard deviation of 0.22 (efficiency 69-100%) (Figure 3). The longer contact time of the treated water with the filtration material contributed to the increased microbiological activity of the beds. The increase in the content of nitrites in the treated water was observed from the first days of the bed's operation (phase I of the nitrification process), and the increase of nitrates in the spill occurred from day 24 (phase II of the nitrification process) (Figure 3). In the water treatment system without pre-activation of the bed (water III), the time of biofilm formation (maturation of the bed) was comparable to the two-stage biofilration system with pre-activation (water II). In this case, a higher efficiency of ammonium nitrogen removal was observed from the first days of the biofilter's operation (effectiveness for the entire test period was 78-97%) and the permissible value of 0.39 mg N-NH\({}_{4}\)\({}^{+}\)/m\({}^{3}\) was obtained more quickly (on the 7 th day) (Figure 4). The values in the outflow were from 0 to 0.7 N-NH\({}_{4}\)\({}^{+}\), with a standard deviation of 0.14. Among the  
Figure 3: Change in the content of nitrite nitrogen compounds after biofilration on the chaledonite bed in the analyzed systems. Figure 2: Change in the content of ammonium nitrogen compounds after biofilration on the chaledonite bed in the analyzed systems. samples analyzed, as many as 90% met the requirements for water intended for consumption. For comparison, in the system with a chemically activated bed, the required level of ammonium nitrogen was achieved only on the 24 th day of the filter's operation. The obtained test results confirm the effectiveness of the biofiltration process on the chalcogenite beds in the removal of ammonium nitrogen from groundwater. Regardless of the analyzed variant, from day 32, the efficiency oscillated in the range from 75% to 100%. In the initial phase of the experiment, a less effective NH4+ elimination was observed in the activated bed system (water III). This phenomenon was caused by a longer time of the formation of the nitrifying biofilm, as evidenced by smaller changes in the content of nitrite and nitrate ions as compared with changes occurring on the non-activated bed (Figures 2-4). The effectiveness of manganese removal was highest in a two-stage biofiltration system activated with KMnO4 solution (water II) (Figure 5). In this case, the efficiency was at a level of 52% -99% and in 30% of the analyzed samples, values below 0.05 g Mn/m3 were achieved. Chalcedonite grains activated with the KMnO4 solution are covered with MnO2 coating and sorb and catalyze the oxidation of manganese at a much faster rate than the unactivated bed. However, the use of only single-stage filtration (water I) did not allow us to obtain satisfactory results in terms of Mn removal either (Figure 5). On the chemically unactivated bed (water III), a reduction in the concentration of manganese after the biofiltration process was observed only in the initial days (up to day 21). This was caused by the low sorption properties of chalcogenite.