Feeding Ammonia and Forming Chloramines. Tom O Connor, PE

Transcription

1 Feeding Ammonia and Forming Chloramines Tom O Connor, PE

2 Outline Chemicals Gear Design Costs

3 Purchasing Ammonia Volatile market Regulated by DEA (used to make crystal meth) 15-day supply on hand

4 How to Make Meth (1) Definitions. Terms frequently used in connec-tion with chlorination practice are defined as follows: (a) Chlorine demand. The difference between the concentration of chlorine added to the water and the concentration of chlorine remaining at the end of a specified contact period. Chlorine demand varies with the concentration of chlorine applied, time of contact, temperature, and water quality. (b) Chlorine residual. The total concentration of chlorine remaining in the water at the end of a speci-fied contact period, (c) Combined available residual chlorine. Any chlorine in water which has combined with nitrogen. The most common source of nitrogen is ammonia, and compounds formed by the reactions between chlorine and ammonia are known as chloramines. The disinfect-ing power of combined available chlorine is about 25 to 100 times less than that of free available chlorine. (d) Free available residual chlorine. That part of the chlorine residual which has not combined with nitrogen. (2) Chlorination practice. (a) Combined residual chlorination, Combined residual chlorination entails the application of suffi-cient quantities of chlorine and ammonia, if ammonia is not present in the raw water, to produce the desired amount of combined available chlorine (chloramine) in a water. If enough ammonia is present in raw water to form a combined chlorine residual, only chlorine need be added to the water. Combined residual chlorination is generally used only when maintaining an adequate free chlorine residual in the distribution system is difficult or when objectionably high levels of TTHMs would be formed as a result of free residual chlorina-tion. Due consideration of other TTHM control alternatives should be made before using chloramines, (see para 2-13). (b) Breakpoint chlorination. If a water contains -- ammonia or certain nitrogenous organic matter which reacts with chlorine, the addition of chlorine causes the formation of chloramines until the ratio of ele-mental chlorine to ammonia compounds is about 5 to 1. Further addition of chlorine results in the oxidation of chloramines to gaseous nitrogen and nitrogen oxides, which decreases the quantity of chloramines present. After all of the chloramines have been oxi-dized, additional chlorine added to the water forms only free available chlorine. The point at which all of the chloramines have been oxidized and only free chlo-rine is formed is called the breakpoint. If no am-monia is present in the water, there will be no break-point. The chlorine required to reach the breakpoint is usually about 10 times the ammonia nitrogen content of the water. However, in certain waters, because of the presence of other chlorine consuming substances, as much as 25 times the ammonia nitrogen concentra-tion may be required. Enough chlorine should be added past the breakpoint to ensure an adequate free chlorine residual. (c) Marginal chlorination. Marginal chlorination involves the application of chlorine to produce a de-sired level of total chlorine residual regardless of the relative concentrations of free or combined chlorine present. In marginal chlorination the initial chlorine demand has been satisfied but some oxidizable sub-stances remain. (d) Chlorine dosages. Figure 2-4 provides mini-mum cysticidal and bactericidal free chlorine residuals and minimum bactericidal combined chlorine residuals for various ph and temperature levels. Since water-borne bacteria are the major concern at fixed installa-tions, minimum bactericidal levels will be maintained in treated water in all parts of the distribution system under constant circulation. Even at lower ph levels, free chlorine residuals should not fall below 0.2 mg/l and combined chlorine residuals should not fall below 2.0 mg/l. If marginal chlorination is practiced, the total chlorine residual must not be less than 2.0 mg/l. Whenever epidemological evidence indicates an out-break of a nonbacterial waterborne disease such as amebiasis, infectious hepatitis, or schistosomiasis in the area of a fixed military installation, cysticidal free chlorine residuals shall be maintained in the water supply. Further guidance on disinfection requirements may be obtained from the Surgeon General s office. Air Force policy on minimum chlorine levels is estab-lished in AFR (3) Other effects of chlorination. In addition to the disinfection achieved with chlorination, other beneficial effects should be noted. Since the oxidizing power of chlorine is high, in the presence of free chlo-rine, hydrogen sulfide is oxidized, nitrites are oxidized to nitrates, and soluble iron and manganese are oxi-dized to their insoluble oxides. Free chlorine also re-acts with naturally occurring taste, odor and color-producing organic substances to form chloro-organic

5 Forms of Ammonia Anhydrous Ammonia (Gas) Aqueous Ammonia (Liquid) Ammonium Sulfate (Solid)

6 Which Form to Use? Availability and Cost Safety and Handling Site Considerations 70% of Utilities use Anhydrous

7 Availability and Cost common industrial, agricultural, and commercial chemical produced regionally by Farmland (Lawrence, KS) and GS Robins (St. Louis)

8 Safety and Handling Aqueous Ammonia is safer than Anhydrous Ammonium Sulfate must be kept completely dry

9 Site Considerations Storage Requirements anhydrous is the most concentrated, thus requires the least storage space Spill and Leak Protection Conversion of Existing Equipment

10 Anhydrous Ammonia Gas at ambient temperature and pressure Stored and transported as a liquid in pressure vessels 150 lb cylinder, 5 cylinder minimum order, `~50 /lb delivered Highly soluble in water

11 Aqueous Ammonia Liquid made by dissolving anhydrous ammonia into DI water 18 Baume : Stored and transported in 400 lb (55-gal) PE-lined drum or bulk Stored in low-pressure steel or fiberglass tanks ~13 /lb delivered Need 4,500 gallon tank to see cost benefits of bulk purchasing

12 Bloomington, IL

13 Storage

14 Tank Top

15 Warming Hut

16 Water Line and Injector

17 Gas Flow

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19 Anhydrous Ammonia Feed Flow Signal Control System PRV Anhydrous NH 3 tank trailer Eductor Evaporator (if necessary) V-Notch ammoniator Utility Water Ammoniation Building Solution diffuser (~ 150 psi maximum discharge pressure) Water Softener Brine waste during regeneration Pump Source: Montgomery, Figure 6-6. Anhydrous Ammonia Solution Feed System

20 Anhydrous Ammonia Feed

21 Anhydrous + Chlorine

22 Liquid Vaporizer

23 Anhydrous Gaseous Feed

24 Aqua Ammonia Feed

25 Aqua Ammonia Feed

26 Ammonium Sulfate Feed

27 Pre- Chlorinator

28 OSU - Stillwater, OK

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30 10 CSR 60-xx.aaa Design Standards for Community Water Systems Draft version currently open for public comment Intended to be incorporated into state law

31 Anhydrous Ammonia (I) (II) Anhydrous ammonia storage and handling facilities shall be designed to meet OSHA Standard With rising temperature, ammonia expands rapidly, increasing the internal pressure in vessels and pipes, etc. This shall be considered in the design and operation of ammonia systems. (III) Anhydrous ammonia feeding facilities shall be located in a separate enclosed room that meets all of the requirements of subparagraph (5) (E)1.A. of this rule for chlorine gas feeding facilities. However, only explosion- proof, electric fixtures shall be used in the room. (IV) Anhydrous ammonia contact with chlorine or fluorine can create explosive compounds. Therefore, feeding and storage facility design shall consider methods of preventing ammonia or chlorine leaks from coming into contact with either chemical. Furthermore, fluoride-feeding facilities shall not be located in ammonia feeding or storage rooms.

32 Ammonia Solutions I. Storage (a) Ammonia solutions shall be kept in tightly closed containers stored in a separate cool, dry, ventilated room and kept from all forms of chlorine, strong acids, most common metals, strong oxidizing agents, aluminum, copper, brass, bronze, chlorite or chlorate solutions and other incompatible chemicals. (b) Ammonia solutions shall be protected from direct sunlight. (c) The storage room shall be provided with a separate, corrosionresistant, ventilation system to capture mist or fumes and vent them to the outside. (d) Ammonia solution containers may be hazardous when empty since they retain product residues. Therefore, all warnings and precautions listed for the product should be observed for empty containers.

33 Ammonia Solutions II. Handling (a) Ammonia solutions are very toxic to aquatic life and spills may not be drained into some sanitary sewer systems. Therefore, full spill containment shall be provided. (b) Absorbent pads and the drains, sumps, finished water plumbing, hose bibs and hoses necessary to clean up spills and to wash equipment shall be provided. (c) An emergency plan of operation should be developed for the clean up of any spillage. (d) Provide protective safety equipment for the operators that includes but is not limited to chemical safety goggles, butyl rubber or neoprene gloves, self contain breathing apparatus and water proof outer clothing. (e) To reduce the hazard to the water plant operators ammonia solutions shall not be diluted. Instead, solution with the correct strength for the amount fed shall be purchased or the metering pump specified shall permit the use of undiluted solution for water plants of any size.

34 Ammonia Solutions III. Feeders (a) Positive displacement feeders shall be provided for feeding the ammonia solutions. (b) Methods for accurately metering or weighing the ammonia solutions shall be provided. Graduated-measuring chambers should be built into the feeder piping to allow the feeder output to be routinely checked. (c) Tubing for conveying ammonia solutions shall be Type 1 PVC, polyethylene or materials recommended by the manufacturer. (d) Feed lines shall be installed in a manner to prevent formation of gas pockets and shall terminate at a point of positive pressure. (e) Storage tanks and unsealed carboys or barrels shall be vented to the outside with a vent approved by the department.

35 Disinfection Disinfection with chloramines is not recommended for primary disinfection to meet the CT requirements in a surface water treatment plant or a plant treating groundwater under the influence of surface water. In a conventional filtration treatment plant, softening plant, and iron and manganese removal plant, provisions should be made for applying disinfectant to the influent of each sedimentation basin, filter influent, and water entering the clearwell. Systems using chloramines as the disinfectant residual entering the distribution system must add and mix the chlorine prior to the addition of ammonia.

36 Disinfection For surface water systems and GWUDI of surface water-- (a) The disinfection treatment must provide a sufficient CT (Disinfectant residual concentration multiplied by the contact time) value to ensure that the total treatment process achieves the required inactivation and /or removal of Giardia Lambia cysts and Viruses; (b) The disinfectant contact time must be determined by Tracer Studies as explained in Appendix-B of the Guidance Manual for Surface Water System Treatment Requirements. The tracer study is required to be done for a new treatment plant prior to receiving final approval from the department for permission to operate; (c) The percentage of Giardia Lambia cyst and Virus removal by the disinfection process shall be determined by calculating the CT value and comparing the calculated CT value with the corresponding water characteristics on the CT tables in Appendix-C of the Guidance Manual for Surface Water System Treatment Requirements; and (d) Free residual chlorination is the preferred practice. If the system uses a disinfectant other than chlorine, the system must demonstrate to the department that the treatment process can satisfactorily inactivate and/or provide the required log removal of Giardia Lamblia Cysts and Viruses.

37 Disinfection Disinfectant Residual (I) Only free available chlorine or chloramine shall be used as the disinfectant to water entering the distribution system. Chlorine and chloramine shall be applied prior to the filters with a residual maintained through the filters, to the water entering the distribution system, and at distant points in the water distribution system. Chloramine, when used as disinfectant must provide breakpoint chlorination in the treatment process before converting the chlorine to chloramine. (II) The minimum disinfectant residual of water entering the distribution system shall be 0.5 milligrams per liter of free available chlorine or 2.0 milligrams per liter chloramine. (III) Minimum free residual at distant points in a water distribution system shall be 0.2 milligrams per liter. Chloramine residual, if utilized shall be 1.0 milligrams per liter at distant points in the distribution system. Higher residuals may be required depending on ph, temperature and other characteristics of the water.

38 Disinfection Minimum Disinfectant Residual Minimum disinfectant residual of water entering the distribution system free chlorine: 0.5 mg/l chloramine: 2.0 mg/l Minimum free residual at distant points in a water distribution system free chlorine: 0.2 mg/l chloramine: 1.0 mg/l Higher residuals may be required depending on ph, temperature, and other characteristics of the water.

39 Disinfection Alternative Disinfectants Chloramines Chloramines are generally not suitable as primary disinfectants but may be used to provide required distribution system residuals. The following shall be considered before using chloramines. 1. Existing facilities wanting to install chloramine disinfection shall do a disinfectant profile through the treatment plant and develop an inactivation benchmark. The results of the profile shall be submitted to the department along with the written request to change disinfectants. 2. Nitrites and nitrates are primary health contaminants and must be kept below the maximum contaminant levels. Therefore, sampling in the distribution system shall be done to find if nitrification is occurring.

40 Disinfection Alternative Disinfectants Chloramines 3. Heterotrophic bacteria studies should be done routinely to assure that biological growths are controlled throughout the distribution system. Any study should include sufficient sampling to identify all problem areas. 4. To help control microbial growths, break point chlorination should be obtained before adding ammonia to the water and converting to chloramines. 5. Chlorination facilities must be provided that will allow free chlorine residuals to maintained throughout the distribution system. 6. All systems must notify all of its customers before converting to chloramines. Special care must be taken notify dialysis clinics, doctors clinics, hospitals, nursing homes and home dialysis patients.