Utilización Microbial

Paper: Analytical determination of the microbial utilization and transformation
Municipal refuse originating from a domestic sector of the city of Braunschweig (Germany) was placed in a 40 m3 cylindrical container and compacted mechanically. Technical details of this largein- volume model landfill have been described elsewhere [12].
Mixed samples of the refuse were collected either fresh or 2and12 months after disposal in the landfill. They were dried in air (50 °C), finely milled (<1 mm), and extracted using a standard method for soil humic substances [13]. In brief, samples were extracted with a mixture of NaOH (0.1 mol L–1) and Na2P4O7 (0.1 mol L–1) under an atmosphere of N2 (24 h). The suspensión was centrifuged at 5000×g in a Sorvall model RC5C centrifuge and the brownsupernatant was collected. The solid residue was extracted two or three more times until the extract was only pale yellow. The combined extracts were adjusted to pH 1.5 with HCl (conc.) and humic acids (HA) were left to precipitate over night.
The HA were collected by centrifugation (as above), purified by dialysis against distilled water, then against 0.3 mol L–1 HF, and finally against water. Theremaining ash content was approximately 10%. The material was dried (50 °C), and finely ground in an agate mortar before use in experiments. HA preparations (100 mg) were added to sterile nutrient solution (100 mL) in 250-mL Erlenmeyer flasks, which were closed with cotton plugs.

Paper: Application of alkaline treatment for sludge decrement and humic acid recovery
After alkaline sludge treatmentand centrifugal separation, the supernatant was filtered through a membrane with a mesh size of 0.45 lm. The dissolved organic substances in the filtrate were then measured. A porous ceramic membrane with 23 channels (TAMI Industries, France) was used to extract humic acid from the filtrate. The external diameter of the tubular membrane was25 mm, the length was 1178 mm, the inner diameter of thechannels was 3.5 mm, the membrane area was 0.35 m2, the máximum working pressure was 1.0 MPa, and the adaptable pH range was 0–14.

Paper: Characterisation-of-sewage-sludge-derived-organic-matter-Lipids-and-humic-acids_2003_Organic-Geochemistry
Humic substances were extracted both from raw and solvent-extracted samples. The extraction procedure was based on the IHSS method (Swift, 1996). Sampleswere first extracted by HCl in order to recover the first fraction of fulvic acids (FA) then with NaOH under N2. The alkaline extract was separated from the residue containing humin. Clays and minerals were precipitated by KCl addition, then recovered and added to the humin compartment. The supernatant was acidified at pH 2 with concentrated HCl. Then, humic (HA) and fulvic (FA) acids wereseparated by centrifugation.

Paper: Characterisation and Evaluation of Humic Acids Extracted from Urban Waste as Liquid Fertilisers
The humic acids (HA) of the organic materials were extracted by shaking the samples with 0É1 M P2O7Na4 at pH 9É8 for 24 h. The extracts were centrifuged at 13 200]g. The supernatant was acidiÐed to pH 2 with HCl. The precipitated humic fraction, separated by centrifuging,was submitted to a puriÐcation process consisting of the reduction of the mineral content with 5% HF-HCl (1 : 1, v/v) by heating ; then the humic fraction was dialysed until Na` and K` cations were removed, and Ðnally lyophilised.

Paper: Characterization of Sewage Sludge Humic Substances
Air-dried sludges or leonardite were extracted twice by shaking 10g of sample overnight with 200ml of 0.1MNa4P207 at pH9"8 (Cegarra et al., 1974). The extract was centrifuged twice at 16 300g and the supernatant acidified to pH2 with H2SO4. The precipitate was separated by centrifugation, redissolved in dilute sodium hydroxide (pH 9.8), and dialysed exhaustively against deionized water until a negative Na + and K + test was obtained. After dialysis, the HA were again precipitated at pH2 and...