California Wastewater Treatment Operator Practice Exam 2025 – All-in-One Guide to Master Your Certification

Total suspended solids (TSS) is the sum of non-settleable solids and settleable solids. Non-settleable solids are solids that remain suspended in water and do not settle out over time, while settleable solids are solids that settle out in a given period of time. Therefore, the formula for TSS must include both types of solids, making option A the correct answer. Option B is incorrect because it shows the result of subtracting two different types of solids, which is not an accurate representation of TSS. Option C is incorrect because multiplying two different types of solids is not a valid way to calculate TSS. Option D is incorrect because dividing TSS by settleable solids does not provide a complete picture of all solid particles in the wastewater.