Assessment of the Effect of PHBV-Based Bioplastic Microparticles on Soil Organisms

(1) Background: A bioplastic poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is used in agriculture and in other applications like shopping bags, toys, and containers. Since the production of bio-based plastics, including PHBV-based materials, is expected to increase within the next few years, they are prone to becoming ubiquitous pollutants of the soil compartment. (2) Methods: An innovative PHBV-based plastic material was tested for its effect on higher plants and earthworms at the community level in a small-terrestrial model ecosystem (STME). The leachates obtained from PHBV-based plastic were studied with the use of ecotoxicological tests with regard to their impact on the early stages of the growth of higher plants and with the use of LC/MS toward the identification of the released chemical compounds. (3) Results: PHBV-based plastic microparticles at the relatively high but environmentally relevant concentration of 2.5% w/w neither affected the germination of higher plants nor inhibited their growth. The synthesis of chlorophyll and the C:N ratio in the plant biomass did not deteriorate, but the content of dry matter of the plant biomass was reduced at a statistically significant level. PHBV-based microplastics did not contribute to the mortality of Eisenia andrei, whereas they affected the depth distribution of these earthworms in the soil. Their downward movement indicated the avoidance behaviour under unfavourable living conditions. In the leachates from PHBV-based bioplastic, lactic acid and glycerol triacetate, commonly used plastic additives, were identified. These leachates did not inhibit the germination and the early stages of growth of higher plants. (4) Conclusions: PHBV-based bioplastic was studied at a concentration not higher than 2.5% w/w, and its leachates do not pose a threat to soil biota and should not affect the sustainability of the terrestrial ecosystem

Validation of a new image analysis procedure for quantifying filamentous bacteria in activated sludge

Quantification of filamentous bacteria in activated sludge systems can be made by manual counting under a microscope or by the application of various automated image analysis procedures. The latter has been significantly developed in the last two decades. In this work a new method based upon automated image analysis techniques was elaborated and presented. It consisted of three stages: (a) Neisser staining, (b) grabbing of microscopic images, and (c) digital image processing and analysis. This automated image analysis procedure possessed the features of novelty. It simultaneously delivered data about aggregates and filaments in an individual calculation routine, which is seldom met in the procedures described in the literature so far. What is more important, the macroprogram performing image processing and calculation of morphological parameters was written in the same software which was used for grabbing of images. Previously published procedures required using two different types of software, one for image grabbing and another one for image processing and analysis. Application of this new procedure for the quantification of filamentous bacteria in the full-scale as well as laboratory activated sludge systems proved that it was simple, fast and delivered reliable results.</jats:p