Microbial population, stability and maturity analysis of rotary drum composting of water hyacinth

Abstract

Water hyacinth is a noxious aquatic weed growing over a wide variety of wetland. One of the effective methods of its treatment is rotary drum composting. Hence, microbial succession in the rotary drum composting of water hyacinth was studied along with stability and maturity. Different ratios of water hyacinth, cow dung and sawdust, i.e. 8: 1: 1, 7: 2: 1, 6: 3: 1, 5: 4: 1 and 10: 0: 0 (control), respectively, were taken. A total weight of 150 kg was maintained. Maximum degradation was observed in the trial 3 (6: 3: 1), which showed maximum temperature rise up to 56.5°C. The total mesophilic bacterial count changed from 4.73 × 1012 to 2.5 × 107 colony forming unit (CFU)/g compost during the composting period. Spore forming population reached the highest count of 3.3 × 1010 CFU/g in the thermophilic phase of composting. Actinomycetes, streptomycetes and fungi counts decreased to about 2.4 × 107 CFU/g, 6.5×105 CFU/g and 6.79 × 105 CFU/g, respectively, at the end of composting period. A maximum reduction of 78.7% in oxygen uptake rate and 90.6% in CO2 evolution rate was observed. This showed the highest stability of the compost sample. But the maximum volatile solids reduction of 45.9% signified the high content of recalcitrant lignocellulosic material. Indicator organisms were reduced to acceptable standards of sanitation.