NR 252.02(11)(11) “Retan-wet finish” means the final processing steps performed on a tanned hide including, but not limited to, the following wet processes: retan, bleach, color, and fat liquor. NR 252.02(12)(12) “Sulfide” means total sulfide as measured by the potassium ferricyanide titration method described in s. NR 252.035 or the modified Monier- Williams method described in s. NR 252.036. NR 252.02(13)(13) “Vegetable tan” means the process of converting hides into leather using chemicals either derived from vegetable matter or synthesized to produce effects similar to those chemicals. NR 252.02 HistoryHistory: Cr. Register, October, 1986, No. 370, eff. 11-1-86; am. (12), Register, May, 2001, No. 545, eff 6-1-01. NR 252.03NR 252.03 Sulfide analytical method. NR 252.03(1)(1) The potassium ferricyanide titration method described in s. NR 252.035 shall be used whenever practicable for the determination of sulfide in wastewaters discharged by plants operating in all subcategories except the hair save or pulp, non-chrome tan, retan-wet finish section in s. NR 252.30. In all other cases, the modified Monier-Williams method as described in s. NR 252.036 shall be used as an alternative to the potassium ferricyanide titration method for the determination of sulfide in wastewaters discharged by plants operating in all sections except s. NR 252.30. NR 252.03(2)(2) The modified Monier-Williams method as described in s. NR 252.036 shall be used for the determination of sulfide in wastewaters discharged by plants operating in the hair save or pulp, non-chrome tan, retan-wet finish subcategory pursuant to s. NR 252.30. NR 252.03 HistoryHistory: Cr. Register, October, 1986, No. 370, eff. 11-1-86; r. and recr. Register, May, 2001, No. 545, eff. 6-1-01. NR 252.035NR 252.035 Potassium ferricyanide titration method. The following method is based on method SLM 4/2 described in Official Method of Analysis, Society of Leather Trades’ Chemists, Fourth Revised Edition, Redbourn, Herts., England, 1965 and is to be used for the determination of sulfide in alkaline wastewater. NR 252.035(1)(a)(a) The buffered sulfide solution is titrated with standard potassium ferricyanide solution in the presence of a ferrous dimethylglyoxime ammonia complex. The sulfide is oxidized to sulfur. Sulfite interferes and shall be precipitated with barium chloride. Thiosulfate is not titrated under the conditions of the determination. NR 252.035(2)(a)(a) 0.1 Preparation of 0.02 N potassium ferricyanide; -32.925 g. per liter - this solution must be kept in the dark. Weigh to the nearest tenth of a gram 6.6 g. of analytical reagent grade potassium ferricyanide and dissolve in one liter distilled water. Store in an amber bottle in the dark. Prepare fresh each week. NR 252.035(2)(b)(b) Standardization of ferricyanide solution: Transfer 50 ml. of solution to a 250 ml. Erlenmeyer flask. Add several crystals of potassium iodide, about one g., mix gently to dissolve, add one ml. of 6N hydrochloric acid, stopper the flask, and swirl gently. Let stand for 2 minutes, add 10 ml. of a 30% zinc sulfate solution, and titrate the mixture containing the gelatinous precipitate with standardized sodium thiosulfate or phenylarsine oxide titrant in the range of 0.025-0.050N. Add one ml. of starch indicator solution after the color has faded to a pale yellow, and continue the titration to the disappearance of the blue color. Calculate the normality of the ferricyanide solution using the equation: Normality of Potassium Ferricyanide = (ml of thiosulfate added) X (normality of thiosulfate)
K3 Fe(CN)6 Ml of K3 Fe(CN)6
NR 252.035(2)(c)(c) Preparation of 6M ammonium chloride buffer, pH 9.3: Dissolve 200 g. ammonium chloride in approximately 500 ml. distilled water, add 200 ml. 14M reagent grade ammonium hydroxide and make up to one liter with distilled water. The buffer may be prepared in a hood. Store in a tightly stoppered container. NR 252.035(2)(d)(d) Preparation of 0.05M barium chloride solution: Dissolve 12-13 g. barium chloride dihydrate in one liter of distilled water. NR 252.035(2)(e)(e) Preparation of ferrous dimethylglyoxime indicator solution: Mix 10 ml. 0.6 percent ferrous sulfate, 50 ml. one percent dimethylglyoxime in ethanol, and 0.5 ml. concentrated sulfuric acid. NR 252.035(2)(f)(f) Preparation of stock sulfide standard, 1000 ppm: Dissolve 2.4 g. reagent grade sodium sulfide in one liter of distilled water. Store in a tightly stoppered container. Diluted working standards must be prepared fresh daily and their concentrations determined by EPA test procedure 376.1 (see 40 CFR 136.3, Table IB, parameter 66 (49 FR 43234, October 26, 1984, with correction notice at 50 FR 690, January 4, 1985)) immediately prior to use. NR 252.035(2)(g)(g) Preparation of 10N NaOH: Dissolve 400 g. of analytical reagent grade NaOH in one liter distilled water. NR 252.035(2)(h)(h) Sample preservation and storage: samples are to be field filtered by either gravity or pressure with coarse filter paper, such as Whatman 4 or equivalent, immediately after collection. Filtered samples must be preserved by adjustment to pH> 12 with 10N NaOH. Sample containers must be covered tightly and stored at 4 degrees C until analysis. Samples shall be analyzed within 48 hours of collection. If these procedures cannot be achieved, it is the laboratory’s responsibility to institute quality control procedures that shall provide documentation of sample integrity. NR 252.035(3)(a)(a) Transfer 100 ml. of sample to be analyzed, or a suitable portion containing not more than 15 mg. sulfide supplemented to 100 ml. with distilled water, to a 250 ml. Erlenmeyer flask. NR 252.035(3)(c)(c) Add 20 ml. of 6M ammonium chloride buffer (pH 9.3), one ml. of ferrous dimethylglyoxime indicator, and 25 ml. of 0.05M barium chloride. Mix gently, stopper, and let stand for 10 minutes. NR 252.035(3)(d)(d) After 10 minutes titrate with standardized potassium ferricyanide to disappearance of pink color. The endpoint is reached when there is no reappearance of the pink color after 30 seconds. where
A=volume in ml. of potassium ferricyanide solution used, and
B= normality of potassium ferricyanide solution.
Report results to 2 significant figures.
NR 252.035(4)(a)(a) Each laboratory that uses this method is required to operate a formal quality control program. The minimum requirements of this program consist of an initial demonstration of laboratory capability and the analysis of replicate and spiked samples as a continuing check on performance. The laboratory is required to maintain performance records to define the quality of data that is generated. Ongoing performance checks shall be compared with established performance criteria to determine if the results of analyses are within precision and accuracy limits expected of the method. NR 252.035(4)(b)(b) Before performing any analyses, the analyst shall demonstrate the ability to generate acceptable precision and accuracy with this method by performing the following operations. NR 252.035(4)(b)1.1. Perform 4 replicate analyses of a 20 mg/l sulfide standard prepared in distilled water. See sub. (2) (f). NR 252.035(4)(b)2.a.a. Calculate clean water precision and accuracy in accordance with standard statistical procedures. Clean water acceptance limits are presented in subd. 2. b. These criteria shall be met or exceeded before sample analyses can be initiated. A clean water standard shall be analyzed with each sample set and the established criteria met for the analysis to be considered under control. NR 252.035(4)(b)2.b.b. Clean water precision and accuracy acceptance limits: for distilled water samples containing from 5 mg/l. to 50 mg/l. sulfide, the mean concentration from 4 replicate analyses shall be within the range of 50 to 110% of the true value. NR 252.035(4)(c)(c) The method detection limits or MDL may be determined periodically by each participating laboratory in accordance with the procedures specified in ”Methods for Chemical Analysis of Municipal and Industrial Wastewater,” EPA- 660/4-82-057, July 1982, EMSL, Cincinnati, OH 45268. For the convenience of the user, these procedures are contained in s. NR 252.0365. NR 252.035(4)(d)(d) A minimum of one spiked and one duplicate sample shall be performed for each analytical event, or 5% spikes and 5% duplicates when the number of samples per event exceeds 20. Spike levels are to be at the MDL and at x where x is the concentration found if in excess of the MDL. See par. (c) for MDL samples. Spike recovery shall be 40 to 120% for the analysis of a particular matrix type to be considered valid. If a sample or matrix type provides performance outside these acceptance limits, the analyses shall be repeated using the modified Monier-Williams procedures described in s. NR 252.036. NR 252.035(4)(e)(e) Report results in mg/liter. When duplicate and spiked samples are analyzed, report all data with the sample results. NR 252.035 HistoryHistory: Cr. Register, May, 2001, No. 545, eff. 6-1-01. NR 252.036NR 252.036 Modified Monier-Williams method. NR 252.036(1)(a)(a) Hydrogen sulfide is liberated from an acidified sample by distillation and purging with nitrogen gas (N2). Sulfur dioxide interference is removed by scrubbing the nitrogen gas stream in a pH 7 buffer solution. The sulfide gas is collected by passage through an alkaline hydrogen peroxide scrubbing solution in which it is oxidized to sulfate. Sulfate concentration in the scrubbing solution is determined by either EPA gravimetric test procedure 375.3 or EPA turbidimetric test procedure 375.4 (see 40 CFR 136.3, Table IB, parameter 65 (49 FR 43234, October 26, 1984, and correction notice at 50 FR 690, January 4, 1985)). NR 252.036(1)(b)(b) (apparatus see figure 1.) Catalogue numbers are given only to provide a more complete description of the equipment necessary, and do not constitute a manufacturer or vendor endorsement. Heating mantel and control (VWR Cat. No. 33752-464)
1000 ml. distilling flask with three 24/40 joints (VWR Cat. No. 29280-215)
Friedricks condenser with two 24/40 joints (VWR Cat. No. 23161-009)
125 ml. separatory funnel with 24/40 joint (VWR Cat. No. 30357-102)
Inlet tube with 24/40 joint (VWR Cat. No. 33057-105)
Adapter joint 24/40 to 19/38 (VWR Cat. No. 62905-26)
Adsorber head (2 required) (Thomas Cat. No. 9849-R29)
Adsorber body (2 required) (Thomas Cat. No. 9849-R32)
Laboratory vacuum pump or water aspirator
NR 252.036(2)(a)(a) Potassium hydroxide, 6N: Dissolve 340 g. of analytical reagent grade KOH in one liter distilled water. NR 252.036(2)(b)(b) Sodium hydroxide, 6N: Dissolve 240 g. of analytical reagent grade NaOH in one liter distilled water. NR 252.036(2)(c)(c) Sodium hydroxide, 0.03N: Dilute 5.0 ml. of 6N NaOH to one liter with distilled water. NR 252.036(2)(d)(d) Hydrochloric acid, 6N: Dilute 500 ml. of concentrated HCl to one liter with distilled water. NR 252.036(2)(e)(e) Potassium phosphate stock buffer, 0.5M: Dissolve 70 g. of monobasic potassium phosphate in approximately 800 ml. distilled water. Adjust pH to 7.0 0.1 with 6N potassium hydroxide and dilute to 1 liter with distilled water. Stock solution in stable for several months at 4 degrees C. NR 252.036(2)(f)(f) Potassium phosphate buffer, 0.05M: Dilute one volume of 0.5M potassium phosphate stock buffer with 9 volumes of distilled water. Solution is stable for one month at 4 degrees C. NR 252.036(2)(g)(g) Alkaline 3% hydrogen peroxide: Dilute one volume of 30% hydrogen peroxide with 9 volumes of 0.03N NaOH. Prepare this solution fresh each day of use. NR 252.036(2)(h)(h) Preparation of stock sulfide standard, 1000 ppm.: Dissolve 2.4 g. reagent grade sodium sulfide in one liter of distilled water. Store in a tightly stoppered container. Diluted working standards shall be prepared fresh daily and their concentrations determined by EPA test procedure 376.1 immediately prior to use (see 40 CFR 136.3, Table IB, parameter 66 (49 FR 43234, October 26, 1984, and correction notice at 50 FR 690, January 4, 1985)). NR 252.036(2)(i)(i) Sample preservation and storage: Preserve unfiltered wastewater samples immediately after collection by adjustment to pH>9 with 6N NaOH and addition of 2 ml. of 2N zinc acetate per liter. This amount of zinc acetate is adequate to preserve 64 mg/l. sulfide under ideal conditions. Sample containers shall be covered tightly and stored at 4 degrees C until analysis. Samples shall be analyzed within 7 days of collection. If these procedures cannot be achieved, it is the laboratory’s responsibility to institute quality control procedures that will provide documentation of sample integrity. NR 252.036(3)(a)(a) Place 50 ml. of 0.05M pH 7.0 potassium phosphate buffer in trap no.1. NR 252.036(3)(b)(b) Place 50 ml. of alkaline 3% hydrogen peroxide in trap no. 2. NR 252.036(3)(c)(c) Sample introduction and N 2 prepurge: Gently mix sample to be analyzed to resuspend settled material, taking care not to aerate the sample. Transfer 400 ml. of sample, or a suitable portion containing not more than 20 mg. sulfide diluted to 400 ml. with distilled water, to the distillation flask. Adjust the N2 flow so that the impingers are frothing vigorously, but not overflowing. Vacuum may be applied at the outlet of trap No. 2 to assist in smooth purging. The N2 inlet tube of the distillation flask shall be submerged deeply in the sample to ensure efficient agitation. Purge the sample for 30 minutes without applying heat. Test the apparatus for leaks during the prepurge cycle using snoop or soap water solution. NR 252.036(3)(d)(d) Volatilization of H2 S: Interrupt the N2 flow and vacuum and introduce 100 ml. of 6N HCl to the sample using the separatory funnel. Immediately resume the gas flow and vacuum. Apply maximum heat with the heating mantle until the sample begins to boil, then reduce heat and maintain gentle boiling and N2 flow for 30 minutes. Terminate the distillation cycle by turning off the heating mantle and maintaining N2 flow through the system for 5 to 10 minutes. Then turn off the N2 flow, release vacuum, and cautiously vent the system by placing 50 to 100 ml. of distilled water in the separatory funnel and opening the stopcock carefully. When the bubbling stops and the system is equalized to atmospheric pressure, remove the separatory funnel. Extreme care shall be exercised in terminating the distillation cycle to avoid flash-over, draw-back, or violent steam release. NR 252.036(3)(e)(e) Analyze the contents of trap no. 2 for sulfate according to either EPA gravimetric test procedure 375.3 or EPA turbidimetric test procedure 375.4 (see 40 CFR 136.3, Table IB, parameter 65 (49 FR 43234, October 26, 1984, and correction notice at 50 FR 690, January 4, 1985)). Use the result to calculate mg/l. of sulfide in wastewater sample. where A=mg/l of sulfate in trap no. 2
B=liquid volume in liters in trap no. 2
and C=volume in ml of waste sample distilled
NR 252.036(4)(a)(a) Each laboratory that uses this method shall operate a formal quality control program. The minimum requirements of this program consist of an initial demonstration of laboratory capability and the analysis of replicate and spiked samples as a continuing check on performance. The laboratory shall maintain performance records to define the quality of data that is generated. Ongoing performance checks shall be compared with established performance criteria to determine if the results of analyses are within precision and accuracy limits expected of the method. NR 252.036(4)(b)(b) Before performing any analyses, the analyst shall demonstrate the ability to generate acceptable accuracy and precision by performing the following operations. NR 252.036(4)(b)1.1. Perform 4 replicate analyses of a 20 mg/l. sulfide standard prepared in distilled water. Refer to sub. (2) (h) under “Reagents.”
