Kinetic assessment of biodegradability in gel-forming soil conditioners based on bod analysis

Abstract

Biodegradation is one of the main factors limiting the effi ciency and service life of gel-forming soil conditioners. Th e
study quantifi es this process using laboratory analysis of biological oxygen uptake (BOD) in innovative composite
superabsorbents with an acrylic polymer matrix, amphiphilic agents (humates, peat) and silver ions as an inhibitor
of biological activity. A simple kinetic model of BOD is proposed to standardize the analysis and calculation of the
half-life of polymers aft er their incubation in precision VELP respirometers (Italy). Th e half-life of hydrogels swollen
in distilled water (1:100) at a temperature of 30°C varied in the range from 0,8±0,2 to 2,4±1,6 years. Th e addition
of an aqueous extract from compost sharply enhances biodegradation and reduces the half-life of hydrogels up to
40–60 days. Doses of 0,1–1% silver in a polymer matrix or 10-100 ppm in swollen hydrogels increase their half-life by
5–20 times. Th e new methodological approach makes it possible to fully automatically evaluate the biodegradation
of gel–forming polymers in laboratory conditions, however, for stable materials with a half-life of more than 2,5–3
years, the accuracy of manometric BOD analyzers is insuffi cient for a statistically reliable assessment of the kinetics
of biodegradation even in long (120 days) incubation experiments.