Complex sentence: Seeing sewage contains not only heavy metals and disease pathogens such as Clostridium difficile but nutrients as well, companies such as Synagro embraced the nutrient idea and marketed sludge as "biosolids" to farmers as a free fertilizer.
Split into simpler sentences: Seeing sewage contains not only heavy metals and disease pathogens such as Clostridium difficile but nutrients as well. Companies such as Synagro embraced the nutrient idea and marketed sludge as "biosolids" to farmers as a free fertilizer.