# Neutralization of Toxic Malodorous Gases from Cattle Slurry
## 3 Results
### Deodorization Effect of Cattle Slurry by Microorganisms
The addition of a biopreparation, i.e., _Bacillus subtilis_ KKP 3903/_Pseudomonas fluorescens_ KKP 3909 to the slurry resulted in a 29% increase in the amount of total nitrogen compared to the control sample (0.825 kg/m\({}^{3}\)), as shown in Table 7.  
About 34% of the nitrogen in cattle slurry after the deodorization process by the bacterial consortium was present in the form of easily soluble ammonia nitrogen used by plants. The presence of ammonium-N (NH\({}_{4}\)-N) in the slurry ensures greater nitrogen absorption by plants, which can directly absorb and incorporate it into organic compounds. The difference in ammonia nitrogen variation comparing control and biotreated manure is 38%. The phosphorus content was recorded at 0.295 kg/m\({}^{3}\), which was an increase of 79% compared to the control sample. In the case of using the developed microorganism consortium, the potassium content was approx. 1.278 kg/m\({}^{3}\) (an increase of 6% compared to the control sample). In the sample where the _Bacillus subtilis_ KKP 3903/_Pseudomonas fluorescens_ KKP 3909 microorganism consortium was used, an over two-fold increase in magnesium (0.625 kg/m\({}^{3}\)) and a 29% increase in calcium content (1.148 kg/m\({}^{3}\)) was noted compared to the slurry that was not subjected to deodorization. The sodium content was around 0.936 kg/m\({}^{3}\), which was a 26% increase compared to the control sample. The content of magnesium, calcium, and sodium is usually sufficient to cover the plant's demand for these elements [45]. Due to the use of slurry as a natural organic fertilizer, a comparison of heavy metal concentration in CS before and after the deodorization process was carried out. Heavy metals as environmental pollutants can become strongly toxic for different environmental elements, such as water, soil, and air, due to their persistence and bioaccumulation in biological systems [46; 47]. The following metals were determined: zinc (Zn), iron (Fe), copper (Cu), manganese (Mn), molybdenum (Mo), lead (Pb), chromium (Cr), nickel (Ni), cadmium (Cd) and boron (B). It was found that the use of a deodorization process (with bacterial consortium) had an effect on reducing heavy metals in the cattle slurry. Table 8 shows the content of heavy metals in CS before and after the deodorization process. \begin{table}
\begin{tabular}{c c c} \hline
**Element** & **Control CS** & **Biotreated CS** \\  & [kg/m\({}^{3}\)] & **[kg/m\({}^{3}\)]** \\ \hline Total nitrogen (N) & 0.825 \(\pm\) 0.032 & 1.065 \(\pm\) 0.051 \\ Total phosphorus (P) & 0.165 \(\pm\) 0.020 & 0.295 \(\pm\) 0.011 \\ Total potassium (K) & 1.204 \(\pm\) 0.061 & 1.278 \(\pm\) 0.024 \\ Calcium (Ca) & 0.889 \(\pm\) 0.019 & 1.148 \(\pm\) 0.018 \\ Magnesium (Mg) & 0.268 \(\pm\) 0.011 & 0.625 \(\pm\) 0.022 \\ Sodium (Na) & 0.742 \(\pm\) 0.017 & 0.936 \(\pm\) 0.049 \\ \hline \end{tabular} Notes: The table shows mean values and standard deviations. Samples were analyzed in triplicate.  
\end{table} 
Table 7: Content of macro-elements in cattle slurry (CS) after the deodorization process by bacterial consortium (_Bacillus subtilis_ KKP 3903 and _Pseudomonas fluorescens_ KKP 3909, 1:1). Heavy metal concentrations were measured using a Spectroquant(r) Prove 600 spectrophotometer. It was found that out of the ten heavy metals determined in cattle slurry, in eight of them, a lower content after the detoxification process in the range of 7-23% was noted. These heavy metals were as follows: Zn, Fe, Cu, Mo, Pb, Cr, Ni, and Cd. However, in two cases, i.e., manganese and boron, a higher content was noted after the application of the bacterial consortium, i.e., 2-13%.