Watershed Training Workshop

Transcription

1 Watershed Training Workshop September 2017 Subsurface Sewage Disposal System Design and Function

2 Connecticut Department of Public Health Environmental Engineering Program 410 Capitol Avenue- MS# 12SEW P. O. Box Hartford CT, Phone: (860) Fax: (860)

3 Septic What is sewage? Domestic Sewage Where does it go? Different options for disposal What is a septic system? System components and function How is a system located? New and Repair Vertical and horizontal distances

4 Septic 101 cont. What happens when my system stops working? System Repair Malfunctioning and failed system Pollutants in domestic sewage How do I know my system is not working properly? Signs of failure and malfunction 4

5 What is Sewage? DomesticSewage

6 6 Domestic Sewage

7 Domestic Sewage Water and human excretions Toilets Bathing water shower tub Cooking and cleaning Laundry Waste from restaurants and commercial buildings 7

8 Where does it go? What happens when we flush? 8

9 How we dispose sewage? Where does it go? 9

10 Methods of Sewage Disposal Public Sewers: municipal treatment plant Conventional Septic Systems Alternative or Advanced Treatment Systems 10

11 Public Sewers Serves approximately 70 percent of the CT population Predominantly in urban areas and area of high density development 11

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14 Conventional Septic Systems Served approximately 1 million people in CT Subsurface Sewage Disposal Systems 14

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16 Alternative Treatment Systems Wastewater Management District Legislation may allow for broader use Requires DEEP permit Aerobic Treatment Intermittent Sand Filter

17 17 What is a Septic System?

18 System Components Building Sewer Septic Tank Distribution Piping Leaching System Necessary pumps, grease traps and groundwater control systems Distribution Boxes and Piping 18

19 Building Sewer or Sewer Line Leaching System 19

20 Sewer Line Septic Tank Leaching System Soil Septic effluent percolates at a steady rate into the surrounding soil. Groundwater 20

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23 Building or House Sewer Refers to the pipe located between the building served connecting to the septic tank 23

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25 Septic Tank Provides the primary treatment: separates, settles and digests 25

26 26 Septic Tank

27 Distribution Piping Consists of the piping leading from the septic tank to the leaching system. 27

28 28 Distribution Box

29 29 Perforated Piping

30 Leaching System Properly functioning leaching system should disperse effluent (liquid from the septic tank) into the surrounding soils without breaking out on the ground surface or polluting the groundwater. 30

31 How does a leaching system work? Effluent from the tank is directed to the leaching system by the distribution piping. A layer of biological slime is formed on the interface between the soil and the leaching system surface (BIOMAT). The growth of the slime layer reduces the rate at which sewage passes into the soil. 31

32 Formation of a Biomat (Gravity Distribution) One Day 1-3 Month 3-6 Months 32 6 Months- 1 Year

33 33 Biomat Growth

34 Leaching Types 34 Trench Pits Galleries Proprietary products Plastic chamber Mats Forms Cardboard

35 35 Stone Trenches

36 36 Leaching Pit or Dry Well

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38 38 Galleries 12-inch high

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40 40 Galleries - 27-inch Teepees

41 41 Galleries 4 x 4

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44 44 Plastic Chambers

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47 12 of Stone 47

48 48 Cardboard

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51 51 Low Pressure Distribution System

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57 Cesspools Not Allowed in current code. Many still exist. 57

58 How are systems located? Where should my system go? 58

59 New and Repair Systems :Vertical Placement Utilize soil-based identification What we look for: Color variations in the soil Biogeochemical processes of reduction, movement, and oxidation of Iron and Manganese Actual ground water measured during the wet season Ledge rock Compact soils Any layer that restricts the downward movement of water 59

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62 Vertical Separation Distances Bottom of the Leaching 18 above seasonal high water or compact layer (restrictive layer) 24 if a large system over 2000 GPD Or tidally influenced 4 over ledge rock, 24 of which is natural Ground Water

63 Groundwater Monitoring Wet season monitoring February 1 to May 31 Curtain Drain Monitoring Wells Proposed Leaching System 63

64 64 Horizontal Placement: New Systems

65 What happens when a system stops working? 65

66 When a repair is needed Malfunctioning System Backflow into the structure Backflow into the septic tank at time of tank cleaning Minor system repair Pipe crushed Effluent filter clogged Improper use of the system o Flushing newspaper or kitty litter Failed systems discharge effluent to ground surface or otherwise cause health hazards or nuisance conditions. 66

67 67 Overtime even properly installed systems can experience difficulties if misused or not maintained.

68 Pollutants in Domestic Sewage Suspended Solids Bio-chemical Oxygen Demand (BOD5) Total Nitrogen Total Phosphates Grease and Oils Coliform Bacteria 68

69 Bio-Chemical Oxygen Demand BOD measure of the amount of bio-degradable organic chemicals in the wastes High BOD = strong waste Low BOD = weak waste 69

70 Bio-Chemical Oxygen Demand Properly functioning septic tank will reduce the BOD in the effluent by about 25 to 30 percent (more with a two compartment tank) Further reduction occurs when the effluent comes in contact with bacterial growth in the leaching system (biomat) Amount of reduction depends on the volume of bacterial growth in the leaching system 70

71 Nitrogen Hazardous to infant children (methomoglobinemia or blue baby disease ) Septic systems remove approximately 30% of total nitrogen with the remaining 70% being discharged to the groundwater. 71

72 Phosphate Stimulates plant growth (lush green grass or algae growth in surface water) Readily removed by filtration through only a foot or two of soil. 72

73 Coliform Bacteria indigenous to the tract of humans and warm-blooded animals - may not be harmful themselves, but indicates that pathogenic organisms and / or viruses may be present - viruses are smaller than bacteria and not as easily filtered out 73

74 Chemical Pollutants in Sewage Paints, solvents, refinishing agents, cleaning chemicals, chlorinated hydrocarbons, etc. Considered to be hazardous chemicals since they can readily pass thru a septic system and enter the groundwater Amount of these chemicals in domestic sewage should be extremely small 74

75 How do I know the system is not working properly? What is that smell? 75

76 Before Inspecting Notify the local health department Where and when People may call Findings Notify the public Add in the local paper Post card Do your research Visit the local health department Where are the systems located? 76

77 Signs of Problems Patches of lush green grass or pooling of wastewater on the ground surface. Sewage overflowing on to the ground surface needs immediate attention. Call Local Health Department to report septic failures and problems with any septic system. Locals can issue orders to correct failure Take photos A picture is worth 1000 words! 77

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83 83 No problem

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85 85 Signs of a problem Runback from the leaching fields into the septic tank after pumping could indicate a problem with the leaching portion of the system. Large volume discharges cause either a backup or an overflow of sewage above the septic tank or leaching field. This condition is usually at its worst during and/or directly following a heavy rain event and in times of high groundwater.

86 Use your nose Foul septic odors in storm drainage piping, catch basins, footing drain piping or curtain drain discharges may indicate that sewage is entering these groundwater systems. 86