| Popis: |
Static pile passive aeration composting (SPPAC) method is simple and economical. It can be applied to treat and stabilize animal wastes and reduce their adverse impact on the environment such as water, soil and air pollution. A study was carried out to investigate the effectiveness of SPPAC process for poultry manure slurry treatment under high initial MC conditions, using peat and straw as the bulking agents. Four treatments were examined, two of which were mixtures of poultry manure slurry and peat with initial MC of 73 and 80%. The other two treatments consisted of poultry manure slurry and chopped straw with initial MC of 72 and 76%, these two treatments had similar performances and results. Three replicate piles were monitored simultaneously for each treatment. The piles were trapezoidal and 3.35m$\sp3$ in volume. Two open-ended perforated pipes were laid at the bottom of each pile to provide aeration. A total of 316 thermocouples were installed in the compost piles to monitor temperature over a period of four months. Within 5 days thermophilic temperatures over 45$\sp\circ$C were attained in the compost piles confirming that passive aeration was effective and exothermic composting reactions started rapidly. Temperature distribution results illustrated that air diffusion and convection were the predominant aeration mechanisms. Cluster analysis of the temperature results provided a depiction of passive aeration, i.e., the ambient air was drawn into the compost through the lower parts of the piles to fill the void created by the up-moving heated air in the system. The temperature results also confirmed that the perforated pipes in the bottom of each pile increased aeration only in their vicinity. The compost with high moisture was successfully handled using the SPPAC method, no symptoms of anaerobic conditions were recorded. Mass balance results showed that nitrogen loss was lower in the compost of higher MC and lower pH, maximum 37% and 50% from the peat compost and the straw compost, respectively. Based on the guidelines of the Ontario Ministry of Environment, the final compost contained high levels of essential plant nutrients, the percent of total of nitrogen, phosphorus and potassium was greater than 4%, and the heavy metal levels were low. The peat is a better bulking agent than the straw. The performance among the three replicate piles of each treatment was highly stable and reproducible. The composting process took 30 to 90 days for the process to finish depending on the amount of poultry manure slurry in the different treatments. |
