Application of calcium peroxide as an environmentally friendly oxidant to reduce pathogens in organic fertilizers and its impact on phosphorus bioavailability

Abstract

The article presents the research into hygienizing process of chicken manure using calcium peroxide (CaO2) as an environmentally friendly biological deactivation agent. The influence of the addition of CaO2to chicken manure on the bioavailability of phosphorus was also analyzed. The process of biological deactivation using CaO2, CaO and Ca(OH)2agents was analyzed applying the disk diffusion method. To optimize the effect of the hygienizing parameters, (CaO2concentration, pH, temperature and time) on the reduction of Enterobacteriaceae count the Taguchi method was applied. The content of bioavailable phosphorus was measured with the Egner-Riehm method and determined with spectrophotometry. The reduction in bacterial count followed an increase in the concentration of CaO2in a sample. The optimal experimental conditions (CaO2=10.5 wt.%, pH=9.5, T=40°C, t=180 h) enabled a significant decrease in the Enterobacteriaceae count, from 107cfu/g to 102cfu/g. Analysis of the samples with Egner-Riehm method showed that the phosphorus content decreased with the addition of biocide CaO2: from 26.6 mg/l (for 3.5 wt.%) to 3.5 mg/l (for 10.5 wt.%). These values were slightly higher than the content of phosphorus deactivated with Ca(OH)2i.e., from 11.25 mg/l (for 3.5 wt.%) to 4.49 mg/l (for 10.5 wt.%). The application of CaO2for hygienizing chicken manure enables effective reduction of Enterobacteriaceae count to an acceptable level (below 1000 cfu/g). In comparison with the traditional techniques of hygienization, the application of CaO2has a positive effect on the recovery of bioavailable phosphorus.