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Accumulation of fine suspended solids and colloids in a recirculating aquaculture system (RAS) can be avoided by integrating a membrane filtration unit into the system, where the inclusion of a membrane bioreactor (MBR) may be an alternative. The main purpose of the study was to identify how the feeding regime affected membrane performance and fouling phenomena caused by dissolved and submicron colloidal particles in the system, and how the membrane impacted general water quality and particle characterization. To be able to evaluate membrane performance and fouling behavior, transmembrane pressure (TMP) was monitored and assessed in relation to changes in rearing conditions and different water quality parameters observed. From this study the positive influence on the chosen water quality parameters was apparent, where an improved water quality was observed when including a membrane filtration in RAS. Selected water quality parameters and TMP changed during the experimental period in response to the feeding regime, where algae paste, decaying rotifers and dry feed seemed to contribute the most to membrane fouling. Analysis of the concentration of submicron particles and particle size distribution (PSD) (particles < 1 μm) showed both a higher concentration and a more spread distribution in the rotifer/algae paste and dry feed period compared to the Artemia period, which might explain the observed increase in fouling. This study also showed that adapted procedures for concentrate removal are important to prevent hydrolysis of retained particles in the concentrate and leakage of nutrients and organic matter back to the system. 相似文献
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《Communications in Soil Science and Plant Analysis》2012,43(5):821-834
A field experiment was conducted on an alluvial soil with winter lettuce [Lactuca sativa (L.) cv. Bacio] plants to study, in the second year of testing and in both field and laboratory conditions, the effects of fertilizers—compost by farm residues [(FC, 2.0% nitrogen (N)], mineral (MIN, 21% N), organomineral (OM, 10% N), mycorrhizas inoculum (MYC), wine-production residue [distiller's residue (DR, 3.6% N), anaerobic digestate (AD), and mycorrhizas (ADM)—on soil physical and mechanical parameters. Application of DR plus mycorrhizas improved the available phosphorus (P) and copper (Cu) contents of the surface (0–0.20 m) soil. The soil surface macroporosity increased significantly (>20%) in treatments FC, MYC, and OM, compared to the control. Results of the oedemeter test showed that with a load of 10 daN the compression susceptibility was greater in the compost treatment compared to other fertilizers, whereas with a load of 200 daN this parameter was lower in FC, AD, MYC, and ADM treatments. The least penetration resistance in the 0- to 20-cm layer of AD and MYC treatments showed lesser values and only in treatment AD in the 20- to 40-cm layer. Hydraulic conductivity values were enhanced in AD, MYC, and ADM plots. 相似文献
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