Effect of natural zeolite (clinoptilolite) on microbial decomposition processes in stored pig-slurry solids.

The solid fraction (SF) of pig slurry obtained in the first stage of aerobic slurry treatment was amended with 1 and 2% zeolite (clinoptilolite) and stored for 12 weeks under anaerobic conditions or with turning after 3 and 6 weeks of storage. In addition to that SF was mixed with 2% zeolite, 50% (V/V) sawdust, and both sawdust and zeolite, and stored for 6 weeks with turning after 1 and 3 weeks. Plate counts of psychrophilic, mesophilic, coliform and fecal coliform bacteria, determined during the storage, corresponded to the development of temperature in the core of the substrates. An effect of amendment of SF with zeolite and sawdust on plate counts of selected bacteria was observed, dependent on the zeolite dose. The thermophilic phase was not reached in any of the investigated substrates. The populations of fecal coliforms in the substrate amended with 1% zeolite and turned after 3 and 6 weeks decreased after 11 weeks down to 500 CFU/g substrate.