《MLSS测定国.docx》由会员分享，可在线阅读，更多相关《MLSS测定国.docx（5页珍藏版）》请在三一办公上搜索。
1、MLSS测定国摘自水和废水监测分析方法 Total Suspended Solids Dried at 103105C 摘自美国国家标准Standard_Methods_for_the_Examination_of_Water_and_Wastewater 20th Edition 1. General Discussion a. Principle: A well-mixed sample is filtered through a weighed standard glass-fiber filter and the residue retained on the filter is dr
2、ied to a constant weight at 103 to 105C. The increase in weight of the filter represents the total suspended solids. If the suspended material clogs the filter and prolongs filtration, it may be necessary to increase the diameter of the filter or decrease the sample volume. To obtain an estimate of
3、total suspended solids, calculate the difference between total dissolved solids and total solids. b. Interferences: See Section 2540A.2 and Section 2540B.1. Exclude large floating particles or submerged agglomerates of nonhomogeneous materials from the sample if it is determined that their inclusion
4、 is not representative. Because excessive residue on the filter may form a water-entrapping crust, limit the sample size to that yielding no more than 200 mg residue. For samples high in dissolved solids thoroughly wash the filter to ensure removal of dissolved material. Prolonged filtration times r
5、esulting from filter clogging may produce high results owing to increased colloidal materials captured on the clogged filter. 2. Apparatus A. Muffle furnace for operation at 550C. B. Desiccator, provided with a desiccant containing a color indicator of moisture C. concentration or an instrumental in
6、dicator. D. Drying oven, for operation at 103 to 105C. E. Analytical balance, capable of weighing to 0.1 mg. F. Magnetic stirrer with TFE stirring bar. G. Wide-bore pipets.#(45) H. Graduated cylinder. I. Low-form beaker.#(46) J. Glass-fiber filter disks#(47)* without organic binder. K. Filtration ap
7、paratus: One of the following, suitable for the filter disk selected: 1) Membrane filter funnel. 2) Gooch crucible, 25-mL to 40-mL capacity, with Gooch crucible adapter. 3) Filtration apparatus with reservoir and coarse (40- to 60-m) fritted disk as filter support.#(48) L. Suction flask, of sufficie
8、nt capacity for sample size selected. M. Aluminum weighing dishes. 3. Procedure a. Preparation of glass-fiber filter disk: If pre-prepared glass fiber filter disks are used, eliminate this step. Insert disk with wrinkled side up in filtration apparatus. Apply vacuum and wash disk with three successi
9、ve 20-mL portions of reagent-grade water. Continue suction to remove all traces of water, turn vacuum off, and discard washings. Remove filter from filtration apparatus and transfer to an inert aluminum weighing dish. If a Gooch crucible is used, remove crucible and filter combination. Dry in an ove
10、n at 103 to 105C for 1 h. If volatile solids are to be measured, ignite at 550C for 15 min in a muffle furnace. Cool in desiccator to balance temperature and weigh. Repeat cycle of drying or igniting, cooling, desiccating, and weighing until a constant weight is obtained or until weight change is le
11、ss than 4% of the previous weighing or 0.5 mg, whichever is less. Store in desiccator until needed. b. Selection of filter and sample sizes: Choose sample volume to yield between 2.5 and 200 mg dried residue. If volume filtered fails to meet minimum yield, increase sample volume up to 1 L. If comple
12、te filtration takes more than 10 min, increase filter diameter or decrease sample volume. c. Sample analysis: Assemble filtering apparatus and filter and begin suction. Wet filter with a small volume of reagent-grade water to seat it. Stir sample with a magnetic stirrer at a speed to shear larger pa
13、rticles, if practical, to obtain a more uniform (preferably homogeneous) particle size. Centrifugal force may separate particles by size and density, resulting in poor precision when point of sample withdrawal is varied. While stirring, pipet a measured volume onto the seated glass-fiber filter. For
14、 homogeneous samples, pipet from the approximate midpoint of container but not in vortex. Choose a point both middepth and midway between wall and vortex. Wash filter with three successive 10-mL volumes of reagent-grade water, allowing complete drainage between washings, and continue suction for abo
15、ut 3 min after filtration is complete. Samples with high dissolved solids may require additional washings. Carefully remove filter from filtration apparatus and transfer to an aluminum weighing dish as a support. Alternatively, remove the crucible and filter combination from the crucible adapter if
16、a Gooch crucible is used. Dry for at least 1 h at 103 to 105C in an oven, cool in a desiccator to balance temperature, and weigh. Repeat the cycle of drying, cooling, desiccating, and weighing until a constant weight is obtained or until the weight change is less than 4% of the previous weight or 0.
17、5 mg, whichever is less. Analyze at least 10% of all samples in duplicate. Duplicate determinations should agree within 5% of their average weight. If volatile solids are to be determined, treat the residue according to 2540E. 4. Calculation where: A = weight of filter + dried residue, mg, and B = w
18、eight of filter, mg. 5. Precision The standard deviation was 5.2 mg/L (coefficient of variation 33%) at 15 mg/L, 24 mg/L (10%) at 242 mg/L, and 13 mg/L (0.76%) at 1707 mg/L in studies by two analysts of four sets of 10 determinations each. Single-laboratory duplicate analyses of 50 samples of water and wastewater were made with a standard deviation of differences of 2.8 mg/L.
