MLSS stands for "Mixed Liquor Suspended Solids" which is a term used in wastewater treatment. If we talk about synonyms for MLSS, some commonly used terms are activated sludge, biomass, mixed liquor, flocculants, and organic matter. Activated sludge is a biological process used in wastewater treatment plant to remove organic matter, whereas, mixed liquor is the combination of activated sludge and wastewater. Biomass refers to microorganisms that break down organic waste, and flocculants are chemicals used to clump solids together. Organic matter is a general term used for all kinds of waste material, including food waste, human waste, and plant debris. These synonyms can help in better understanding the process of wastewater treatment.