Disinfection of the water recovered from drying of aquaculture scallop sludge

Abstract

A substantial volume of saline sludge with high water content is generated by the aquaculture industry, particularly during bivalve production. The reclamation of water from this sludge becomes particularly crucial in arid regions. This study is the first of its kind to focus on recovering water from sludge produced during the aquaculture of scallops and the subsequent disinfection of this water to remove heterotrophic microorganisms. The method employed involved a solar still followed by a condensation system for water recovery. We obtained 250 kg of wet sludge from the industrial production of scallop culture (Argopecten purpuratus) through the rotary drum filter, which is used for lantern washing. This sludge was subjected to drying in a solar still dryer. The vapor generated during the drying process was condensed using a heat exchanger, resulting in the recovery of 1680 mL of water, accounting for 91% of the sludge mass, with a Gain Output Ratio of 1.6. The recovered water underwent disinfection using various methods, including UV-A, UV-A/O3, UV-C, UV-C/O3, and O3. Among these, the UV-C/O3 process demonstrated the highest removal of Total Cultivable Bacteria, achieving complete disinfection within 60 min of treatment. UV-C was the second most effective treatment, with a bacteria removal rate of 99.92% in the same timeframe. Electrical energy used to reduce bacteria concentration by one order of magnitude was 12.96 kWh/m3 when UV-C process was applied, and 32.92 kWh/m3 when UV-C/O3 process was applied. In conclusion, this study showcases that a significant quantity of water can be reclaimed from scallop sludge through a combination of solar drying and a condensation system. Moreover, this recovered water can be efficiently disinfected using the UV-C/O3 process.