## 3 Results and Discussion
### N-Nh\({}_{4}\)\({}^{*}\) Removal from Coke Wastewater
From the fourth to the twelfth day of the study, in wastewater inoculated with microalgae (without clinoptilolite) (Figure 1A,B) at a dose of 100 and 50 g/L (samples: 10 CvA/10 ScA, 10 CvB/10 ScB, 5 CvA/5 ScA, and 5 CvB/5 ScB), regardless of the form of their occurrence, the concentrations of ammonium nitrogen varied within a range of 59-100, 76-101, 87-101, and 83-101 mg N-NH4\({}^{+}\)/L, respectively. At that time, the concentration of ammonium nitrogen in the control samples was 102-112 mg N-NH4\({}^{+}\)/L. The first portion of wastewater was replaced after ten days of testing. The microalgae without clinoptilolite (Figure 1A,B) needed few days to adapt to the new environment with a higher concentration of contaminants each time after the addition of the new portion of fresh wastewater. During that time, the concentration of ammonium nitrogen remained at a high level for both microalgal strains because no assimilation processes occurred. On the contrary, it was found that in the case of a mixture of microalgae with clinoptilolite and in wastewater with clinoptilolite (without microalgae, Figure 1C), the concentration of N-NH4\({}^{+}\) in wastewater was below 63 mg N-NH4\({}^{+}\)/L. Clinoptilolite had an impact on the lowering of the concentration of nitrogen ammonium in those samples. Concentrations of clinoptilolite stayed the same during the experiment, and clinoptilolite sorbed N-NH4\({}^{+}\) by means of fast physicochemical reactions. The algae needed more time to assimilate N-NH4\({}^{+}\) during their growth. At that time, the concentration of ammonium nitrogen in the control samples was 112-215 mg N-NH4\({}^{+}\)/L. The next (second) portion of wastewater was replaced after 20 days, and thereafter, the concentration of ammonium nitrogen only in samples with a mixture of microalgae and clinoptiolite dropped below 65 mg N-NH4\({}^{+}\)/L (Figure 1C), and in wastewater with clinoptiolite, the concentration of ammonium nitrogen did not exceed 64 mg N-NH4\({}^{+}\)/L. In wastewater samples with immobilized microalgae (Figure 1A), the concentration of ammonium nitrogen did not exceed 197 mg N-NH4\({}^{+}\)/L for _C. vulgaris_ and 222 mg N-NH4\({}^{+}\)/L for _S. armatus_ when the dose of both microalgae strains was 50 g/L, and it did not exceed 182 mg N-NH4\({}^{+}\)/L for _C. vulgaris_ and 184 mg N-NH4\({}^{+}\)/L for _S. armatus_ in the sample where the content of microalgae was 100 g/L. At that time, the least effective removal of ammonium nitrogen using microalgae in the form of suspension was at the level of 195-215 mg N-NH4\({}^{+}\)/L. At that time, the concentration of ammonium nitrogen in the control samples was 251-253 mg N-NH4\({}^{+}\)/L. The third portion of wastewater was replaced after 30 days. A concentration of ammonium nitrogen below the value of 65 was observed only in wastewater samples with the addition of a mixture of _C. vulgaris_ and clinoptiolite, and with the addition of clinoptiolite (Figure 1C). The mixture of _S. armatus_ and zeolite facilitates a concentration of ammonium nitrogen below 135 mg N-NH4\({}^{+}\)/L. In wastewater samples with the addition of microalgae immobilized in both doses (50 and 100 g/L) on the carrier, the concentration of ammonium nitrogen did not exceed 199 mg N-NH4\({}^{+}\)/L. At that time, the concentration of ammonium nitrogen in wastewater samples containing microalgae in suspension was below 228 mg N-NH4\({}^{+}\)/L for _C. vulgaris_ and 276 for _S. armatus_ mg N-NH4\({}^{+}\)/L (Figure 1A,B). At that time, the concentration of ammonium nitrogen in the control samples was 284-288 mg N-NH4\({}^{+}\)/L. Microalgae can act as a pollutant sorbent only after the end of their period of adaptation to new environmental conditions. This time is longer the more polluted the environment is. In all the samples containing microalgae, the ammonium nitrogen removal efficiency was lower than in the samples containing a mixture of microalgae with clinoptiolite, and with the addition of clinoptiolite.