Evaluation of the biosolids compost maturity in south Isfahan wastewater treatment plant
As a promising alternative for biosolids disposal, land application of composted biosolids has increased in the past decade (Goldstein and Steuteville, 1996). One of the important factors affecting the successful use of biosolids compost for agricultural purposes is stability and maturity it. Application of unstable or immature compost may cause slow plant growth and damage crops by competing for oxygen or causing phytotoxicity to plants due to insufficient biodegradation of organic matter. Because extensive research has been conducted to study the composting processes and to develop methods to evaluate the stability and maturity of compost prior to its agricultural use Qimenez and Garcia, 1992; Mathur et at., 199Th Jannotti et at., 1994; Hue and Liu,1995). The terms “compost stability” and “compost maturity” are frequently used in the scientific literature. Compost stability defmition is the rate or degree of organic matter decomposition. As such, compost stability can be expressed as a function of microbiological activity; it can be determined by 02 uptake rate, CO2 production rate, or by the heat released because of microbial activity (Chen and Inbar, 1993; lannotti et at., 1994). Compost maturity refers to the degree of decomposition of phytotoxic organic substances produced during the active composting stage; it can be assessed by plant or seed testing (Zucconi et at., 1981; lannotti et at., 1994). Understanding and properly defining compost stability and maturity, will assist standardization and regulation of the methods used to evaluate compost quality.