REATMENT OF PANGASIUS POND SLUDGE USING EARTHWORMS (PERIONYX EXCAVATUS): OPTIMIZATION OF ORGANIC DECOMPOSITION FOR ORGANIC FERTILIZER AND WORM BIOMASS PRODUCTION

Abstract

    The pangasius farming industry in Ben Tre currently plays a pivotal role, significantly contributing to Vietnam’s seafood export revenue. However, intensive high density farming practices have generated substantial amounts of pond sludge, estimated at approximately 1 to 1.5 tons for every ton of harvested fish. This sludge contains high levels of organic matter, nitrogen, and phosphorus. If not properly treated, it can severely pollute water and soil resources and release greenhouse gases, thereby posing direct threats to surrounding ecosystems and local communities. Against this backdrop, this study was conducted to evaluate the potential application of earthworms (Perionyx excavatus) for treating pangasius pond sludge. It also aimed to optimize the mixing conditions of sludge with coir and the initial worm stocking density, thereby enhancing organic decomposition efficiency and producing nutrient-rich vermicompost and protein-rich worm biomass. The experiment was arranged following a central composite design (CCD) combined with response surface methodology (RSM), investigating three main factors: the sludge-to-coir ratio (80–100%), the coir proportion (0-20%), and the initial worm mass (1-3 kg). Results showed that optimal conditions were achieved with a sludge-to-coir ratio of 90:10 and an initial worm mass of 2 kg, yielding 3.45 kg of worm biomass and 9.47 kg of vermicompost after 43 days of treatment. The resulting vermicompost generally met Vietnam’s QCVN 01-189:2019/BNNPTNT standards for pH, C/N ratio, nitrogen, and phosphorus contents. This treatment model not only helps mitigate environmental pollution in pangasius farming areas but also generates organic fertilizer that improves soil quality and produces worm biomass that can be used as an aquafeed ingredient, supporting the development of circular and sustainable aquaculture systems aligned with green agricultural practices.