THE EFFECTS OF EXTREMELY HIGH DENSITY SEPTIC SYSTEMS ON SURFACE WATER QUALITY IN GWINNETT COUNTY, GEORGIA

Transcription

1 THE EFFECTS OF EXTREMELY HIGH DENSITY SEPTIC SYSTEMS ON SURFACE WATER QUALITY IN GWINNETT COUNTY, GEORGIA John Anderson Georgia Perimeter College Lawrence Kiage Georgia State University

2 Geographic Setting Where in the world is Gwinnett County, Georgia

3 What do we know about the County?

4 Land Use Classification Water 1% 1% Urban 25% 42% Forest 67% 54% Grass 7% 3%

5 Sewers to Septic

6 Septic

7 Sewer 68% Septic = 32% By number of properties Now 487 septic systems/sq. mile Total number of Septic systems = 85,574 Sewer = 55% Septic = 45% By area (acres)

8 If 625 septic systems/sq. mile Reduction of septic systems = 29,395 By numbers Septic = 21% Sewer = 79% By area Septic = 23% Sewer = 77%

9 Yellow River and Alcovy River Basins In Gwinnett County, Georgia Y1 A1 Y3 Y2 A2 A3 A4 Yellow River Basin Y1 = Little Suwannee Creek Y2 = Pew Creek Y3 = Yellow River Snellville Y4 = Yellow River Lithonia Y4 Alcovy River Basin A1 = Hopkins Creek A2 = Shoal Creek Headwater A3 = Shoal Creek lower A4 = upper portion of the Alcovy River Basin

10 Yellow River Basin Y1 = 9.9 mi 2, 2,459 septic Y2 = 7.3 mi 2, 798 septic Y3 = mi 2, 27,36 septic Y4 = mi 2, 39,191 septic Y3 Y4 Y1 Y2 A2 A3 A1 A4 Alcovy River Basin A1 = 1.9 mi 2, 374 septic A2 = 5.4 mi 2, 39 septic A3 = 8.7 mi septic A4 = 3.8 mi 2, 3,19 septic Yellow River Basin Y1 = 67 sep/mi 2, 37% Y2 = 738 sep/mi 2, 15% Y3 =784 sep/mi 2, 26% Y4 = 786 sep/mi 2, 31% Alcovy River Basin A1 = 656 sep/mi 2, 3% A2 = 476 sep/mi 2, 12% A3 = 43 sep/mi 2, 17% A4 = 332 sep/mi 2, 3%

11 Key Water Quality Measures Water Temperature Specific Conductance Hydrogen Ion concentration ph Dissolved Oxygen Biochemical Oxygen Demand Various Nitrogen measures Metals Mg, Mn, Cd, Cr, Cu, Pb, Fe, Zn Phosphorus Coliform Total, Fecal E. coli

12 Rain Data Total Rainfall 7-days prior 14-days prior 21-days prior 28-days prior Amount of Rainfall 1 week prior 2 weeks prior 3 weeks prior 4 weeks prior Number of days of rain 7, 14,21,28 Amount of rain fall immediate before water quality reading Average rainfall 7,14,21,28 Amount of rain that fell on the day of the water quality reading

13 day Total Rainfall y =.6x R² =.18 Linear () Linear () 2 y =.37x R² =

14 Relationship of fecal coliform to the rainfall prior to the reading/duration/time before reading and rainfall Yellow River Basin Slug 1/duration/day from rainfall to reading y =.8x R² =.128 Alcovy River Basin (Slug 1/duration of rainfall)/days prior y =.37x R² =.2763

15 Biologicals and nutrients Ammonia and organic nitrogen y = 1E-5x R² =.941 Linear () y =.3x R² =.4227 Biochemical Oxygen demand y =.3x R² =.6918 Linear () Linear () y =.5x R² =.352 Phosphorus unfiltered y = 3E-6x R² =.1284 Linear () Linear () y = 5E-5x R² =.4198 Dissolved Oxygen y = -2E-5x R² =.428 Linear (Y4-712) y = -.4x R² =.1392

16 Water Conditions Turbidity Field ph y =.33x R² =.1384 Linear () y =.356x R² =.2219 y = -7E-6x R² =.149 Linear (Y4-712) y = -8E-5x R² =.1395 Hydrogen ion concentration Specific conductance y = -.7x R² =.154 Linear (Y4-712) y = -.47x R² =.939 y = 3E-9x +.2 R² =.1151 Linear (Y4-712) 5 1 y = 9E-8x R² =.1998

17 Water temperature and Pew Creek Y2 Water Temperature 3 Water Temperature y = 3E-5x R² =.69 Linear (Y4-712) y =.13x R² = /24/ /6/1999 4/19/21 9/1/22 1/14/24 5/28/25 1/1/26 2/22/28 7/6/29 11/18/21 4/1/212 Water Temperature

18 Runoff car parts Metals Lead unfiltered y = 5E-5x R² =.124 Linear (Y4-712) y =.128x R² =.573 Zinc unfiltered y =.6x R² =.78 Linear (Y4-712) y =.49x R² =.5666 Copper unfiltered y =.1x R² =.854 Linear (Y4-712) y =.95x R² =.473 Chromium unfiltered y =.1x R² =.95 Linear (Y4-712) y =.159x R² =.42

19 More Metals Manganese unfiltered y =.2418x R² = y =.7249x R² =.968 Linear (Y4-712) Magnesium unfiltered y = 5E-5x R² =.1971 Linear (Y4-712) y =.2x R² =.2574 Iron unfiltered y = x R² =.7468 y = x R² = Linear (Y4-712) Flushing Iron unfiltered day total Rainfall y = 197.5x R² =.6847 Linear () Linear () y = 138.4x R² =.27

20 Flushing Water Temperature and total rainfall /2/1999 : Water Temperature and total rainfall /21/1998 : 2/9/1999 : Yellow River near Snellville - Y3 Water Temperature 7-day total rainfall Coliform 3/31/1999 : Yellow River near Snellville - Y3 Water Temperature 7-day total rainfall Coliform /9/1999 : 3/1/1999 : 3/21/1999 : 4/1/1999 : 4/3/1999 : 5/2/1999 : 6/9/1999 : 6/29/1999 : 5/2/1999 : 7/9/1999 : Water Temperature and total rainfall /9/1999 : 8/28/1999 : 1/17/1999 : 12/6/1999 : Water Temperature 7-day total rainfall Coliform /29/1999 : 7/19/1999 : 8/8/1999 : 8/28/1999 : Runoff or is it flushed? Yellow River near Snellville - Y3 9/17/1999 : 1/7/1999 : 1/27/1999 :

21 Oh no! Yellow River Annual Mean Year Y1 Y2 Y3 Y4 Annual Average Yellow River Y Years Wetter year more hits the fan 21-day total rainfall Average total rainfall 21-days

22 Yellow River Axis Title Y1 Y2 Y3 Y4 Y1 = 37%, Y4= 31% Alcovy River Year Geography Y1 A1 A1 A2 A3 A4

23 Annual Mean Comparison Year Y1 Y2 Y3 Y4 A1 A2 A3 A4 Annual Mean - 25 to Y2 A2 Year The Drought

24 Conclusions There is a positive correlation between the amount of rainfall to the water quality readings. There is an increase in the fecal coliform with increased discharge of the stream which is a factor of the amount of rainfall prior to the water quality measurements. There is a positive correlation between fecal coliform and water temperature.

25 Conclusions There is evidence for flushing of septic effluent to the surface to be the cause of the high fecal coliform levels in the water. (Water temperature and rainfall, plus the increase in iron, magnesium, and possibly manganese.) The classic relationships of higher fecal coliform causes an increase in the BOD and a decrease in DO.

26 Conclusions Higher fecal coliform caused by more rainfall causes a lower specific conductance in the water due to dilution. (the solution to pollution is dilution) There are seasonal variations in the amount of fecal coliform in the water.

27 Further work Look at age of septic systems to see if there is any relationship to failing septic systems? (Data needed from County to do this) Water temperature and fecal coliform Improve the septic system map with better data. (I am working on this.)

28 Yellow River well named?