Accelerating nutrient release and pathogen inactivation from human waste by different pretreatment methods

The limitation of hydrolysis and the health risks from pathogenic microorganisms are challenges in the treatment of human waste for volume reduction and nutrient recovery. In this study, potassium ferrate (PF), peroxymonosulfate (PMS), and PF combined with peroxymonosulfate (PMS+ PF) were used as pretreatment or co-treatment methods to enhance nutrient release and control pathogenic microorganisms in human waste. The PF pretreatment was the most effective regarding hydrolysis and organic matter release. The largest difference (D-value) in the soluble chemical oxygen demand (3117.0 mg/L) between the control and the treatment after 120 min was observed for the PF pretreatment, followed by the alkaline (ALK) pretreatment (1525.0 mg/L), the PF + PMS pretreatment (1169.3 mg/L), and the PMS pretreatment (1020.6 mg/L). The PF pre-treated waste exhibited the highest volatile solids reduction of 79.2% after 120 min compared with 15.0% reduction of the untreated waste, as well as the highest polysaccharide release, with a D-value of 198.5 mg/L. All pretreatments exhibited inactivation of pathogenic bacteria and helminths eggs; however, the PF pretreatment was the most efficient method to suppress pathogenic micrograms, with a 3.5 log (N/N0) decrease in the number of total coliforms. The PF pretreatment and PMS + PF co-treatment both exhibited the good performance regarding nitrogen release, including soluble protein and ammonium. The maximum D-value of the total soluble nitrogen was 372.8 mg/L for the PF + PMS co-treatment. The maximum D-value of soluble protein was 156.2 mg/L for the ALK pretreatment. The results indicated that the PF pretreatment was the most effective method for disintegrating human waste, thus providing a new method for safe and rapid reduction of human waste, as well as nutrient release.