Which statement regarding polyelectrolytes is false?

Polyelectrolytes are polymers that demonstrate electrolyte properties and can be either positively or negatively charged, which allows them to interact with various particles in wastewater treatment processes. The statement concerning their cost suggests that they are inexpensive to use, which is not universally accurate. In practice, the expense of polyelectrolytes can be significant, especially when considering the required types and doses, making the treatment process more costly in certain applications.

The other statements about polyelectrolytes highlight crucial aspects of their functioning. An overdose or under dose indeed leads to poor results, as achieving the right balance is essential for effective coagulation and flocculation. The specific pH range requirement is also critical because the charge of polyelectrolytes can change with pH, affecting their performance in treatments. The fact that polyelectrolytes can also possess multiple charges further emphasizes their versatility and importance in wastewater management. This understanding of their characteristics is vital for optimizing their usage for effective treatment outcomes.