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.

Remediation of amide pesticide-polluted soils by combined solarization and ozonation treatment

Agriculture has a close relationship with nature,but it can also be the source of negative and permanent environmental effects.The use of pesticides in modern agriculture is a common practice,but their side effects on the environment cannot be disregarded.In this study,we evaluated a combination of solarization and ozonation techniques for the elimination of six amide pesticides(boscalid,chlorantraniliprole,cyflufenamid,fluopyram,napropamide,and propyzamide)in soil.Initial experiments were performed with four different soils to assess the efficiency of this methodology at different soil temperatures and ozone dosages under laboratory conditions,and then a greenhouse pot experiment was conducted under controlled conditions during summer.Fifty days after the onset of the experiments,higher degradation percentages of amide pesticides were observed in ozonized soils than in other treated soils,particularly when ozone was applied at 10 cm soil depth.The results show that the utilization of ozonation,along with solarization,represents a valid method for degrading residues of the studied pesticides and suggest that this combined technology may be a promising tool for remediating pesticide-polluted soils.

In situ stabilization of arsenic in soil with organoclay,organozeolite,birnessite,goethite and lanthanum-doped magnetic biochar

Arsenic(As)is a known carcinogen and naturally occurring semi-metal in soils and in the Earth's crust.Contamination of soils and water with As poses a serious threat to millions of people worldwide due to its health hazards and toxicological properties.Hence,devising novel and efficient methods for remediation of contaminated areas has attracted a great deal of interest across the globe.In this study,we investigated the usefulness of synthetic birnessite,goethite,hexadecylpyridinium chloride-modified montmorillonite(HDPC-M),hexadecylpyridinium bromide-modified zeolite(HDPB-Z),and lanthanum(La)-doped magnetic biochar produced from eucalyptus bark(La-Euchar)as adsorbents at 10%dosage for As stabilization in a soil spiked with 1000 mg kg^(-1)As.The effectiveness of the above adsorbents in As immobilization in soil was assessed using single-step extractions with 2 mol L^(-1)HNO_(3)and deionized water,the simplified bioaccessibility extraction test(SBET)method,and sequential extraction with the modified Community Bureau of Reference(BCR)method.Application of the adsorbents shifted the exchangeable fraction of As to more recalcitrant fractions and dramatically reduced the exchangeable fraction by 6%-99%and the extractable amounts with HNO_(3),deionized water,and SBET method by 30%-92%,17%-95%,and 12%-90%,respectively,compared to the unamended control.The immobilizing effects of adsorbents on As decreased in the sequence of birnessite>La-Euchar>goethite>HDPB-Z>HDPC-M.Birnessite exhibited great affinity for As and drastically reduced As extractability by more than 90%in all single extractions.The results revealed that HDPC-M,HDPB-Z,La-Euchar,birnessite,and goethite are promising immobilizing agents for in situ stabilization of As in terrestrial environments.