HPMA: Generally less biodegradable due to its polymeric structure, but it has low toxicity and is safe for many applications.

ATMP: More biodegradable than HPMA but can persist in the environment. It has low toxicity and is considered relatively safe.

Summary of Differences:

Feature	HPMA	ATMP
Chemical Type	Polymer	Small molecule (phosphonate)
Primary Function	Dispersant, scale inhibitor	Chelant, scale inhibitor, corrosion inhibitor
Action	Disperses particles, modifies crystals	Chelates metal ions
Thermal Stability	High	Moderate
Applications	Cooling systems, boilers, RO systems	Cooling towers, oilfields, boilers
Environmental Impact	Lower biodegradability	More biodegradable, low toxicity

Both are highly effective in water treatment but are chosen based on specific system needs, such as temperature, fouling, and metal ion presence.