MeWUA Presentation February 7, 2018

Transcription

1 MeWUA Presentation February 7, 2018

2 Development of this BMP Manual is directed at two groups: 1. Those water systems that currently have either part or all of their system within an MS4 community 2. All other water systems within the State of Maine not within an MS4 community.

3 The 1987 CWA amendment required EPA or delegated States to issue permits for the following types of Stormwater discharges Discharge subject to an NPDES permit before February 4, 1987; Discharge associated with industrial activity, including construction ; Discharge from a municipal separate storm sewer system (aka MS4) serving a population of 100,000 or more, and A discharge that an NPDES permitting authority determines to be contributing to a violation of a water quality standard or a significant contributor of pollutants to the waters of the United States

4 Discharges under the General Permit may not Contain any pollutant which may cause/contribute to any adverse impact on receiving water Be a receiving water that is not meeting its classification which may be effected by the discharge Impart color, taste, turbidity or other properties that cause receiving water to be unsuitable for designated uses ascribed to its classification.

5 The General Permit - Defined Municipal Separate Storm Sewer Systems. Regulated stormwater discharges. Permit is issued every five years. Requires permittee to prevent and minimize the discharge of pollutants from the permittee s stormwater conveyance system (MS4) through implementation of a Stormwater Program Management Plan.

6 40 regulated entities were identified: 30 municipalities. 8 State and Federal facilities. 2 transportation entities (MTA & MDOT).

7 Under the the MDEP General Permit allowable discharges include: hydrant discharge for water main flushing discharges from potable water sources firefighting activity runoff So long as the discharges do not contribute to the non-attainment of water quality standards

8 MS4 entities are required to ensure that drinking water utilities have procedures in place to prevent the exceedence of the water quality standards during both planned and unplanned maintenance events.

9 Currently, water systems within non-ms4 communities are not required to submit evidence that they do not discharge chlorinated water into water resources. MDEP staff has not indicated immediate plans to require documented compliance from water systems other than those within MS4 communities However, MDEP staff has reminded all water system operators that discharge of chlorinated water into water resources could be considered a violation of the Federal Clean Water Act previously discussed.

10 Maine DEP has Provided draft guidance for MS4s reviewed by MWUA, MRWA, MeWEA, MMA. Received comments, revised guidance and finalized permits for MS4 systems. Important to note that the General Permit Standards for these discharges does not impact anything inside the drinking water treatment or conveyance systems.

11 Maine DEP and EPA understand that Chlorine is common for drinking water disinfection. However, aquatic organisms are much more susceptible to chlorine toxicity than humans.

12 EPA and Maine have long standing aquatic life chlorine toxicity criteria for fresh and marine waters. Addressing potential aquatic life chlorine toxicity is a common issue for wastewater discharges, and in Maine an emerging issue for drinking water discharges.

13 In 1986 the United States Environmental Protection Agency established ambient water quality criteria for total residual chlorine (TRC) concentration for receiving waters based on acute (short-term) and chronic (longer-term) toxic effects for aquatic life such as fish and aquatic insects. Maine has adopted these water quality criteria.

14 To meet Maine s ambient aquatic life water quality criteria for fresh water, the TRC concentration in a waterbody must not exceed 19 micrograms per liter (ug/l) for acute exposure, and 11 ug/l for chronic exposure. To meet Maine s ambient aquatic life water quality criteria for marine water, the TRC concentration in a waterbody must not exceed 13 ug/l for acute exposure, and 7.5 ug/l for chronic exposure. Because a discharge from a drinking water system through a MS4 is likely to be a relatively short term event, the acute criteria noted above should be used for any determinations of nonattainment.

15 Maine DEP staff has indicated through their Issue Profile their agreement to use 0.05 mg/l as the concentration that must be attained in the water resource. This is based upon the current accuracies of the field equipment available for measuring chlorine concentration.

16 In January of 2017 a Task Force Committee was organized by Maine Rural Water Association and Maine Water Utilities Association to develop a BMP Manual that water systems could use as a guideline for compliance. Development of the BMP Manual was funded by the Maine Drinking Water Program.

17 The Committee has met numerous times to discuss the regulatory requirements and to develop the components of the BMP Manual. The Committee has worked with Snowden Consulting Engineers to develop the BMP Manual.

18 The BMP Manual is intended to be used for the following water system operations: Bi-annual (or annual) hydrant flushing for water quality within water system Emergency repairs and post repair flushing Trench dewatering from draining water main Flushing when disinfecting new water main installations per AWWA chlorination standards. Draining of storage tanks, reservoirs or clear wells. Other chlorinated water discharges to the environment.

19 Many water systems currently use equipment that disperses the chlorinated discharge such as: Truck mounted diffuser boxes with fire hose inlet connections Diffuser units mounted on the end of fire hose The following slides show some examples of the equipment that is and has been used by water systems to discharge to the environment.

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23 Chapter 1 Dechlorination Flowchart

24 A flow chart was established for the manual that provides a quick resource for water system operators to utilize when selecting an appropriate BMP for a particular discharge.

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26 Chapter 2 Introduction

27 The BMP Manual looks at two different options for selection of BMP s for chlorinated discharge. These include: Non-chemical dechlorination for Total Residual Chlorine Concentrations that are less than 4 mg/l. Chemical dechlorination for Total Residual Chlorine Concentrations that are greater than or equal to 4 mg/l.

28 Recommended that water systems develop a Standard Operating Procedure (SOP) for planned and emergency discharges. MDEP recommends that PWS discharging to an MS4 system have these procedures in place, on file, with appropriate training to those employees working with system discharges.

29 Sample SOP for Emergency Chlorinated Discharges (such as a water main break) might include use of the following equipment: Trench dewatering pump Silt sock, staked hay bales, crushed stone for stone berm, catch basin rim filter bag, or other such erosion control material. Dechlorination mat, sock or other mechanism to dechlorinate the discharged water. Possibly install stone berm in ditch, with dechlorination mat upstream of the berm in ponded area. Filter bag over CB inlet with dechlorination mat installed within filter bag. Silt bag with dechlorination tablets installed in the bag.

30 Several important factors for Public Water Systems in emergency situations include: MDEP recognizes that timely and safe operations are the highest priority for PWS Resolve the emergency as quickly as possible to minimize the volume of chlorinated discharge Have equipment and materials on hand for dechlorination efforts. This should be set up in the SOP as the quickest option available for the majority of possible emergencies that may occur in the PWS.

31 Chapter 3 System Evaluation for Discharge Locations

32 Chapter 3 System Evaluation for Discharge Location Review system map to determine locations of current chlorinated water discharge points Larger water systems can locate these discharge using GPS instrumentation and include on GIS Mapping Review flushing and discharge locations to determine proximity to water resources. Evaluate options for moving the discharge locations of these discharge points to areas that have less impact on the water resources. Evaluate options for moving discharge locations to areas where non-chemical BMP s may be used rather than chemical BMPs.

33 Chapter 4 Chlorine Monitoring & Record Keeping

34 Chapter 4 Chlorine Monitoring and Record Keeping Use the Chlorinated Discharge Field Form included in the BMP Manual or other form that provides data to backup BMP selection. Ensure that BMP s selected are appropriately meeting the regulations. Once the water system has shown that a BMP selection meets the regulatory standards (BMP manual suggests at least 2 discharge events), future monitoring of each discharge event at this location can be reduced to periodic verification checks as determined by the water system operators.

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36 Chapter 4 Chlorine Monitoring and Record Keeping (Continued) Water system operator should maintain the records of which BMP selections were made for all discharge locations, and have Discharge Field Forms kept on file.

37 Chapter 5 Non-chemical Methods

38 Chapter 5A Dilution of Discharge

39 Two means of estimating flow of water resource 1. Estimate the flow of the water resource chlorinated discharge will be directed into. For rough estimate measure the velocity timing a floating object over a specified distance. Measure the rough cross sectional area where the velocity was measured. Use Q = VA equation(q flowate (cfs), V velocity (ft/sec), A area (s.f.) to estimate stream flow rate.

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41 Two means of estimating flow of water resource (Cont) 2. If data is lacking on flow in the water resource, estimate flow based upon use of BMP chart and comparison using Google Earth, USGS maps, or other mapping systems. Determine the required flow rate for the chlorinated discharge

42 Calculate the required water resource flow to ensure that the TRC concentration in the resource will not exceed the regulatory standards. Disperse the chlorinated discharge as much as possible to promote mixing with the non-chlorinated flow in the resource. Monitor the TRC concentration at the discharge point and in the resource to ensure regulatory standards are met.

43 Important consideration: Flush when there is the greatest dilution in the MS4 and the receiving water.

44 Chapter 5B Discharge into Sanitary Sewer

45 Early planning discussions with Sanitary Sewer System owner or operator to determine potential for use. Are there limitations on the flow into the sewer system at the discharge location, such as a downstream pump station, etc. Can the piping downstream of the discharge point handle the required chlorinated discharge flow? Will the chlorinated discharge into the sanitary sewer negatively impact the sewer treatment process? Determine the backflow prevention requirements and discuss with the Drinking Water Program

46 Chapter 5C Discharge using Land Application

47 Plan the use of equipment that will appropriately disperse the water to maximize the contact of the chlorinated water discharge with the ground materials. Use energy reducing device such as a diffuser tank connected to a truck or diffuser connected to hose to disperse water. Inspect area where discharge will be released to be sure there are no ditches, channels or other such site conditions that will minimize the sheet flow condition.

48 Determine the length from the discharge point to the water resource. Implement erosion control devices if necessary. Determine any negative impact to land or vegetation destruction from TRC concentrations. Monitor TRC concentrations at discharge point and prior to entering water resource throughout the duration of the discharge event.

49 MDEP suggests discharge overland if possible. (with consideration for erosion, property rights, surface waters.)

50 Chapter 5D Operation & Maintenance Techniques

51 Techniques to Minimize impact on Water Resource Evaluate the water system discharge locations to see if new locations can be selected to minimize impact on water resources. Determine if timing of discharge event can occur during high water flows in the water resource, such as early spring or late fall. Determine if implementing either full or partial system Uni-directional Flushing is a viable option.

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53 Techniques to Minimize impact on Water Resource (Continued) Uni-directional flushing does provide a reduction in volume and flow rate by concentrating on flushing through individual pipe sections to maximize scouring velocities. Uni-directional flushing is completed by water system personnel closing valves on looped areas of the water system to direct the flushing water through particular pipe segments. By directing all flushing through one pipe, the minimum required velocities of 2.5 ft/sec are achieved at lower flow rates, as compared to a conventional flushing where multiple pipes will contribute to the discharge, reducing the velocity from each.

54 Techniques to Minimize impact on Water Resource (Continued) Due to their configurations, some systems may not be able to use uni-directional flushing. These water systems should consider spot areas for uni-directional flushing to minimize the impact on water resources.

55 Chapter 5E Discharge to Pavement and/or Storm Water Systems

56 Determine the flow path length for the chlorinated discharge either over pavement and/or through the storm water drainage system present. Field inspect the site to verify that there are no grease, oil or other substances downstream of the discharge location.

57 As evidenced from previous studies by AWWA, the decay rate for chlorinated discharge over pavement or concrete is very low. (One AWWA study included as Exhibit in Appendix of BMP Manual) Chlorinated discharge over grass/topsoil provides much faster decay rates due to the organic materials present.

58 Other discharges within this BMP include discharge to a closed storm drain piping system, vegetated ditches or swales, etc. The assumption for discharge into drainage piping systems is that there will be very little organics present in the piping systems to use up the TRC concentration. Therefore these would likely act as pavement when looking at chlorine decay. When using vegetated ditches or swales, careful consideration should be made to determine the depth of flow from the discharge. Generally speaking, the greater the depth of flow in the ditch, the less contact all of the water column will have with the organics, which will reduce the potential for chlorine concentration reduction.

59 Direct flow over paved surface for as long as possible (maximize sheet flow length). Use fire hose and catch basin mats to direct flow.

60 Chapter 6 Chemical Dechlorination Options

61 Water systems should consider the current water quality of the water resource into which the discharge is to flow For instance, operators may wish to avoid using sulfates or sulfites in areas where water resource has a low dissolved oxygen content, as these chemicals will reduce the dissolved oxygen in the discharge flow and potentially further reduce the DO in the receiving water. Some dechlorination chemicals have an effect on ph, so the operator should be sure that ph changes will not adversely impact the water resource.

62 AMERICAN WATER WORKS ASSOCIATION Chemical dechlorination is a faster and more predictable method of dechlorination and can be accomplished with little or no effect on the environment or personal safety. Solid, liquid, and gaseous dechlorination chemicals are commercially available and are widely used.

63 Water system operators should be sure that they do not overfeed the dechlorination chemical, since many of these chemicals are used in tablet form, this may be difficult. The suggestion would be for the operator to use only enough of the chemical tablets to ensure the discharge meets the regulatory requirements. Some suppliers suggest using the tablet systems in parallel if having trouble meeting the TRC concentration standards with one assembly.

64 Images showing some equipment available for use to dechlorinate the discharge is shown on the following slide.

65 Use commercial dechlorination units as needed. Proper selection of chemical and dosage is important!

66 Treatment Chemicals commercially available include Sulfate salts, Sulfur Dioxide Ascorbic Acid, Sodium Ascorbate

67 Chapter 6A Sulfite Salts, Sulfur Dioxide

68 Sulfite/Sulfate products available include Sodium Sulfate/Sulfite Sodium Bi-Sulfite Sodium Metabisulfite Sodium or Calcium Thiosulfate Sulfur Dioxide

69 Sulfite salts and Sulfur Dioxide all have varying impacts on water quality such as: Tend to lower the ph in the Discharge Water Some scavenge Dissolved Oxygen in the Discharge water Some produce toxic odors or pungent odors when mixed with water Some reduce the Alkalinity

70 Chapter 6B Ascorbic Acid, Sodium Ascorbate

71 Vitamin C chemicals for dechlorination available include: Ascorbic Acid (Vitamin C) Sodium Ascorbate (Vitamin C)

72 Ascorbic Acid and Sodium Ascorbate Forms of Vitamin C chemicals Do not impact ph levels other than for high dosages Do not impact Alkalinity Do no impact Dissolved Oxygen other than for high dosages Have 3-year shelf life in solid form (if sealed) Vitamin C concentrations do not appear to have negative affect on aquatic species

73 Chapter 6C Equipment and Techniques

74 Dechlorination Diffusers are available for both tablet and liquid injection into the chlorinated discharge.

75 Water System Dechlorination BMP Manual

76 Water System Dechlorination BMP Manual

77 Dechlorination Mats are available for chemical tablet dispersement into the chlorinated discharge.

78 Water System Dechlorination BMP Manual Tablet Dechlorination Mat

79 Water System Dechlorination BMP Manual Tablet Dechlorination Mat

80 Dechlorination Socks are available for chemical tablet dispersement into the chlorinated discharge.

81 Water System Dechlorination BMP Manual Tablet Dechlorination Sock

82 Dechlorination Mixing Tanks are available for chemical tablet, powder and liquid dispersement into the chlorinated discharge.

83 Water System Dechlorination BMP Manual Dechlorination Mixing Tanks

84 Chapter 6D Monitoring Equipment

85 Water System Dechlorination BMP Manual Free Chlorine Field Test Kit capable of measuring 0.05 mg/l

86 Water System Dechlorination BMP Manual Optional Equipment may include ph test kit

87 Water System Dechlorination BMP Manual Optional Equipment may include Dissolved Oxygen test kit

88 Sample Local Water District Equipment

89 KK & W Water District Snuffy

90 Snuffy in action

91 Maine Water Company Unit

92 Maine Water Company Chemical Dechlorination system

93 The hope is that use of this manual will provide more options for water systems to consider when discharging chlorinated water to the environment. The manual provides both non-chemical and chemical means of dechlorination for water system operations. The hope is that systems will look to non-chemical means of dechlorination initially, and use chemical dechlorination when non-chemical options are not appropriate.

94 Questions (?)