1、Cyanide Discharges in the Petroleum Industry: Sources and AnalysisAPI PUBLICATION 4750 NOVEMBER 2008Cyanide Discharges in the Petroleum Industry: Sources and AnalysisRegulatory and Scientific Affairs DepartmentAPI PUBLICATION 4750 NOVEMBER 2008Special NotesAPI publications necessarily address proble
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11、d be submitted to the Director of Regulatory and Scientific Affairs, API, 1220 L Street, NW, Washington, D.C. 20005.Abstract When water quality criteria for cyanide are incorporated in NPDES permits, the resulting water quality-based effluent limits may be very low (e.g., 5-20 g/L). This is especial
12、ly true when a discharge is to a surface water body with very little allowable effluent dilution (i.e., a limited mixing zone). Because both industrial and municipal dischargers have been issued NPDES permits with these low effluent limits, there has been considerable interest in the reliability of
13、the available test methods at these low concentrations. This report provides guidance on the measurement, as well as the presence and environmental fate, of cyanide compounds and related chemical species in petroleum industry wastewater effluents. The report provides technical information to assist
14、NPDES permittees in negotiating site-specific water quality-based effluent limits for cyanide. The report also provides permittees with guidance on the sampling and analytical methods that must be used to assure that cyanide data are as reliable as practical, given the limitations of the analytical
15、methods. Addressed within the report are analytical methods frequently specified for measuring total cyanide and simple cyanides, including available cyanide, weak acid dissociable cyanide, and free cyanide. All of the analytical methods for cyanide are subject to matrix interferences when wastewate
16、r and surface water samples are analyzed, and method performance testing is recommended for cyanide concentrations below 30-50 g/L. i Table of Contents Table of Contents . i List of Tables . ii Executive Summary . iii Chapter 1: Introduction 1 Properties of Cyanides and Related Chemicals 2 Cyanide .
17、 2 Related Chemicals 3 Petroleum Industry Sources 3 Chapter 2: Water Quality Criteria . 5 EPA Water Quality Criteria 5 Fresh Water Criteria 6 Marine Water Criteria . 7 State Water Quality Standards 8 States Using EPA Criteria . 8 States With Criteria Different from EPAs . 9 Summary of State Cyanide
18、Criteria 10 Chapter 3: Cyanide in Refinery Wastewaters . 11 Sources 11 Chemical composition 12 Summary . 13 Chapter 4: Cyanide in non-Petroleum Wastewaters 15 Industrial Discharges 15 POTW Discharges 17 Chapter 5: Analytical Methods. 20 Description of Methods for Cyanide Analysis 22 Total CN 22 Simp
19、le CN . 24 Detection Methods 26 Related Compounds 27 Method Performance . 29 Detection and Quantitation Limits 29 Precision and Recovery. 32 Interferences 35 Preliminary Treatment of Samples . 37 Chapter 6: Summary . 39 References 42 ii List of Tables Page 1 EPA and State Water Quality Criteria For
20、Cyanide 7 2 Industrial Categories with EPA Technology-based Limits 17 for Cyanide 3 2001 TRI Releases of Cyanide to Surface Waters 17 4 POTW Cyanide Effluent Discharges 18 5 Analytical Methods for Cyanide Forms 22 6 Methods for Cyanide-Related Analytes 22 7 Method Detection Limits for Cyanides 27 8
21、State and EPA Quantitation Levels for Cyanide 29 9 Precision and Recovery of a 5 g/L Spike of Simple Cyanide 31 in Various Aqueous Matrices 10 Additional Data on Precision and Recovery 35 of Simple Cyanide from Aqueous Matrices 11 Interferences in Analyses for Cyanide 36 iii Executive Summary The ch
22、emical functional group cyanide (CN) is found on a number of inorganic and organic compounds. Chemicals containing CN have considerable environmental importance because when CN is present as free cyanide hydrocyanic acid (HCN) and the CN- anion it is highly toxic to many life forms. Cyanide complexe
23、s with alkali metals (sodium, potassium), and certain metals such as cadmium and zinc, that dissociate readily in water and exert toxicity equivalent to free cyanide. Cyanide present in stable complexes with metals such as iron and cobalt is not typically toxic in wastewater and surface water. Organ
24、ic cyanides (nitriles) are also generally less toxic to aquatic life than simple cyanides. The U.S. Environmental Protection Agency (EPA) has published water quality criteria for free cyanide. These criteria are very low, on the order of 1-20 g/L. Most states have adopted the EPA water quality crite
25、ria as water quality standards and may apply them as either free cyanide or total cyanide. Free cyanide criteria expressed as total cyanide are very conservative because of the assumption that stable metal-cyanide complexes will exert toxicity to aquatic life that is equivalent to free cyanide. The
26、stable metal-cyanide complexes can dissociate to free cyanide when exposed to ultraviolet light. Because ultraviolet light is attenuated rapidly by suspended material in an ambient surface water column and by the water itself, however, the rate at which free cyanide is released from metal-cyanide co
27、mplexes will generally be so low that there is a negligible potential for free cyanide to reach toxic concentrations. When water quality criteria for cyanide are incorporated in NPDES permits, the resulting water quality-based effluent limits may be very low (e.g., 5-20 g/L). This is especially true
28、 when a discharge is to a surface water body with very little allowable effluent dilution (i.e., a limited mixing zone). Wastewaters containing cyanide are generated only in the refining sector of the petroleum industry, and then only in a few processes. The sour water streams generated by thermal c
29、racking and visbreaking, catalytic cracking, hydrocracking, delayed coking, and fluidized bed coking are the refinery wastewater streams that will contain potentially significant amounts of cyanide and thiocyanates. Cyanides are formed in these processes because they operate in the absence of oxygen
30、 (i.e., in a reducing environment), and the nitrogen present in the hydrocarbon streams will react at the heat and pressure of these processes to form cyanide. Historically, the amount of cyanides in these wastewater streams has not been considered of regulatory concern because the typical refinery
31、treatment processes (oil and solids separation, biological treatment) remove them efficiently. Refiners have also found that adding polysulfides to thermal cracking wastewaters will efficiently convert simple cyanides to thiocyanates, which will not convert back to cyanide during wastewater treatmen
32、t. This has proven to be an effective method for complying with cyanide limits for most petroleum refineries. However, because the water quality-based effluent limits for cyanides may be very low for some refineries (i.e., 12.0; Immediate addition of sulfamic acid if the sample may contain nitrites
33、and/or nitrates (to reduce the nitrites/nitrates to nitrogen gas); Refrigeration of the sample at 4 C until analysis. Before analysis, if the sample contains sulfide, add lead acetate or lead carbonate to precipitate the sulfide. These actions will minimize interferences, but cannot guarantee accura
34、te and precise measurements at low cyanide concentrations in all effluent matrices and surface waters. Therefore, it is prudent to conduct matrix-specific performance testing, as recommended above, if a permittee must comply with permit limits based on cyanide concentrations below 30-50 g/L. 2 This
35、means in the field, when the sample is collected. vi Glossary of Terms Amenable cyanide Cyanide in a water or waste sample that can be oxidized by free chlorine. Also known as cyanide amenable to chlorination and abbreviated as CN(A), this is the pollutant parameter that is measured by a specific an
36、alytical method and the result is intended to represent free cyanide plus simple cyanides. Complexed cyanide The cyanide anion associated that is with an alkali and a metal such as iron or cobalt. Potassium ferrocyanide is considered a complexed cyanide. Complexed cyanide compounds are usually very
37、stable in water (i.e., they do not readily dissociate to HCN). Cyanate An anion in which the carbon that is bonded to the nitrogen has a covalent bond to oxygen (-O-C N- ). This anion is correctly abbreviated as OCN-, but some references abbreviate it as CNO-. Free cyanide Unionized hydrocyanic acid
38、 (HCN) in aqueous solutions. HCN is the form of cyanide most toxic to aquatic life. Fulminate An anion in which oxygen is bonded to nitrogen, which in turn is bonded to carbon (-CN+-O-). Abbreviated as CNO. Isocyanate The functional group N=C=O covalently bonded to a hydrocarbon, i.e., R-NCO. Nitril
39、e The functional group CN covalently bonded to a hydrocarbon, i.e., R-CN. Thiocyanate An anion in which the carbon that is bonded to nitrogen is also bonded to sulfur (-S-C N- ). Abbreviated as SCN-. Simple cyanide The cyanide anion associated with an alkali or metal. Examples are potassium cyanide
40、(KCN) and cuprous cyanide (CuCN). Simple cyanides readily dissociate in water to HCN because HCN is a weak acid (pK = 9.2). Weak acid dissociable cyanide Cyanide liberated from aqueous solution with the pH adjusted to 4.5-6.0 Standard Units (SU) by an acetate buffer. Abbreviated as CN(W), this is a
41、pollutant parameter that is intended to measure only the simple and free cyanides in the aqueous sample. Zinc acetate is added to the sample to precipitate out iron cyanides and ensure they are not measured as CN(W). American Petroleum Institute Chapter 1 Cyanide Discharges in the Petroleum Industry
42、 1 Introduction Chapter 1 The American Petroleum Institutes (API) Clean Water Issues Task Force (CWITF) commissioned this report to provide information and guidance to its members on the importance, presence, environmental fate, and analytical methods for cyanide compounds and related chemical speci
43、es that may be found in petroleum industry wastewater effluents. A principle objective of this report is to provide technical information that will assist NPDES permittees in negotiating site-specific water quality-based effluent limits. The report also provides permittees with guidance on the sampl
44、ing and analytical methods that must be used to assure that cyanide data are as reliable as practical, given the limitations of the analytical methods. There are currently no national effluent limitations guidelines for cyanide and related chemicals that are applicable to petroleum industry discharg
45、es. However, the U.S. Environmental Protection Agency (EPA) has adopted water quality criteria for cyanide (EPA, 1985) under the authority of Section 304(a) of the Clean Water Act (CWA). All of the states and territories have used EPAs criteria, either directly or with modifications, to adopt water
46、quality standards for cyanide under the authority of Section 303(c) of the CWA. Because the water quality standards for cyanide are uniformly very low, and because certain petroleum industry wastewaters contain cyanides, it is important for API member companies to have information resources that wil
47、l: (1) assist them in participating in future regulation development by the states; (2) provide technical support for the development of NPDES permit limits, and (3) provide technical support for determining the levels of treatment required to achieve water quality-based effluent limits (WQBELs) tha
48、t may be included in NPDES permits. Also, although this study did not identify in any states any stream segments impaired by cyanide, there is always the possibility that such a identification could occur and that a total maximum daily load (TMDL) evaluation for cyanide would then be required. The i
49、nformation in this report will be helpful in such cases, if they were to occur. American Petroleum Institute Chapter 1 Cyanide Discharges in the Petroleum Industry 2 Properties of Cyanides and Related Chemicals The chemical functional group cyanide (CN) is found on a number of inorganic and organic compounds. Chemicals containing CN have considerable environmental importance because when CN is present as free cyanide (hydrocyanic acid (HCN) and the CN- anion), it is highly toxic to many life forms. There are several other functional groups that contain the CN
