Book excerpt: The manual identifies most of the problem organisms found in water supplies and provides recommendations for removing or inactivating them. Chapters describe and illustrate each organism, explain the types of problems it can cause, and offers suggestions for treatment or control. Nonpathogenic organisms covered include actinomycetes, iron bacteria, sulfur bacteria, nitrifying bacteria, nematodes, bloodworms or midges, crustacea, rotifers, zebra mussels, algae, and protozoa.