Integrated bioremediation techniques in a shrimp farming environment under controlled conditions

This study investigated the integrated bioremediation techniques for a shrimp culture system to reduce unconsumed feed and the contents of suspended solids（SS）, nutrients and organic pollutants using barracuda,clamworm, scallop, large algae and a biofilter. A multi-pool internal circulation system was designed to test the effectiveness of the techniques in the laboratory. The experimental result has shown that Argopecten irradians,Gracilaria lemaneiformis and the biofilter efficiently reduced the contents of SS, dissolved inorganic carbon（DIC）and dissolved organic carbon（DOC） in the breeding wastewater. The amount of unconsumed feed was significantly reduced by barracuda and clamworm, but there was an increase in the contents of SS, DIC and DOC in the water due to disturbance by the barracuda and clamworm. The capacity of macroalgae to extract inorganic nitrogen was insufficient. However, the balance of the nitrogen fixation rate of macroalgae and the biological exhaust nitrogen rate within the system should be fully considered. The use of the biofilter alone was not optimal for the remediation of organic matter in shrimp effluent so that auxiliary foam separation technology is needed to improve the ability of the system to remove macromolecules. This study provides a basis for the further development of remediation techniques to reduce the environmental impact of shrimp aquaculture.

Combining Solvent Extraction and Bioremediation for Removing Weathered Petroleum from Contaminated Soil

This study aimed to evaluate the efficacy, practicality and sustainability of a combined approach based on solvent extraction and biodegradation to remediate the soils contaminated with high levels of weathered petroleum hydrocarbons. The soils used in this study were obtained from the Shengli Oilfield in China, which had a long history of contamination with high concentrations of petroleum hydrocarbons. The contaminated soils were washed using a composite organic solvent consisting of hexane and pentane （4：1, v/v） and then bioremediated in microcosms which were bioaugmentated with Bacillus subtilis FQ06 strains and/or rhamnolipid. The optimal solvent extraction conditions were determined as extraction for 20 min at 25 ~C with solvent-soil ratio of 6：1 （v/w）. On this basis, total petroleum hydrocarbon was decreased from 140000 to 14000 mg kg-1, which was further reduced to 〈 4000 mg kg-1 by subsequent bioremediatton for 132 d. Sustainability assessment of this integrated technology showed its good performance for both short- and long-term effectiveness. Overall the results encouraged its application for remediating contaminated sites especially with high concentration weathered hydrocarbons.