The study looked at how adding sewage sludge to soil affects the microbes living in it. They found that adding sewage sludge increased the amount of microbial activity in the soil, like enzymes that help plants grow. The more sludge they added, the more active the microbes became. They also found that the variety of microbes in the soil increased, meaning more types of microbes were able to break down different kinds of food. This shows that using sewage sludge can help improve soil quality and reduce the need for chemical fertilizers.