Potassium-rich mining waste addition can shorten the composting period by increasing the abundance of thermophilic bacteria at high temperature period

Conventional compost sludge takes a long time in the fermentation process and is not full of nutrients. Potassium-rich mining waste was used as an additive for aerobic composting of activated sludge to make a new sludge product. The effects of different feeding ratios of potassium-rich mining waste and activated sludge on physicochemical properties, thermophilic bacteria community structure during aerobic composting were investigated. The results showed that potassium-rich waste minerals contribute to the increase of mineral element content; although the addition of potassium-rich waste minerals affected the peak temperature and duration of compost, the more sufficient oxygen content promoted the growth of thermophilic bacteria, and thus shortened the overall compost period. Considering the requirements of composting temperature, it is recommended that the addition of potassium-rich waste minerals should be less than or equal to 20%.