Elimination of Chronic Total Coliform Presence in a Gravel Packed - - PowerPoint PPT Presentation

“Elimination of Chronic Total Coliform Presence in a Gravel Packed Well Through Enhanced Well Redevelopment”

Rebecca McEnroe, P.E., Superintendent, Sudbury Water District, Sudbury, MA. Savas Danos, General Manager, Panton-McLeod – Americas, Groton, MA

Sudbury Water District

Sudbury Water District

• Population 18,300
• Average Day = 1.8 MGD
• 9 wells, flow range = 300-600 GPM
• Wells 2A, 7 and 9 treated at the Raymond Rd

WTP.

• RRWTP, Mn and Fe removal, corrosion

control, fluoride addition and disinfection

Well 9 Water Quality

• Hardness 140 mg/l
• Mn 1.5 mg/l
• Fe 1.75 mg/l
• TOC 2.5 mg/l
• UV 0.22 cm-1
• Turbidity = 0.55 NTU

Well 9

• 75 ft deep X 24” diameter gravel pack well
• Drilled in 1989
• Total Coliform present in intermittent samples

starting around 2010

• MaDEP approved Ground Water Rule CT for

RRWTP

• 2014-15 19 of 24 sample were TC present (79%

present)

Well 9

• Researched well design and installation to

determine if there were any structural issues causing the total coliform presents within the well

• Met with two different well installers to

visually inspect the well

• Could not determine if there were any

structural issues with the well

Well 9

• Original specific capacity = 125 gpm/ft
• Specific capacity prior to cleaning = 83.3

gpm/ft (33% reduction in capacity)

• Records were not available for the last well

cleaning but antidotal evidence indicated the last well cleaning was before issues with total coliform presents

Well Redevelopment

• Scheduled a well rehabilitation for January

2016

• Typical acid redevelopment was specified
• Decided to use Pantonitetm PM77after acid

redevelopment to see if it would help with TC issue.

• Well went back on-line February 2016

Well screen before cleaning

Well screen after cleaning

Results

• February – October 2016 (9) All sample absent

for TC

• November 2016 – January 2017 (3) TC present
• February – March 2017 (2) All TC samples absent
• 3 of 14 samples present for TC (22% present)
• Positive samples may be a result of very dry soils

due to the drought followed by very heavy rains in October

Signs of Well Degradation

Decrease in Specific Capacity (gal/ft) Decrease in Wire- to-Water Efficiency Water Quality Degradation Decrease in Output (gal/minute)

Causes of Well Output Reduction

• Lower Water Table due to Drought or Aquifer

Depletion

• Reduced Pump Efficiency due to worn, corroded

and/or plugged pumping parts

• Mineral Plugging (Iron, Manganese, Calcium

Carbonate)

• Microbial Corrosion (Sulfate-Reducing Bacteria)
• Mud, sand and/or silt fouling
• Slime Formation (bio-fouling) caused by iron and

slime forming bacteria

Typical Signs of Fe/Mn Plugging

Typical Well Rehabilitation Methods for Iron/Manganese Removal

• Pre & Post Bore Hole Video
• Mechanical Pre-Cleaning/Brushing
• Acid Treatment/Injection (pH 3 or below for 24-48

hours)

• Surging
• Discharge/Neutralization
• Chlorination/Disinfection

Well Screen – New vs. Used!!!!

Typical Disinfection/Acid Treatments

• Chlorine:
• Most effective as disinfectant after chemical treatment – polishing.
• Ineffective at removing biofilm
• Mineral Acids
• Hydrochloric (muriatic): mineral build-up, inexpensive, dangerous (fuming)
• Phosphoric: mineral build-up, non-harmful vapors, slow reacting, phosphates?
• Sulfamic: slow reacting w/ mineral buildup, dry form non-dangerous
• Organic Acids
• Glycolic (hydroxyacetic): some effectiveness on bio-film, non-corrosive
• Glacial Acetic (Vinegar): sulfate removal, organics, very corrosive
• Oxalic: some effectiveness on bio-film.
• Citric: mn/fe removal
• Concerns: NSF Certified?; Are Minerals the only

problem/concern?

When Typical Treatment(s) Stops Working

20 40 60 80 100 120 140 1 2 3 4 5 6 7 8 9 10 11 12 Specific Capacity (g/ft) Months After Treatment

Specific Capacity Evaluation 0.98 mg/l Mn 0.50 mg/l Fe

Acid Blend Acid Blend Enhanced Treatment

Time For Enhanced Redevelopment!

Why Typical Treatments loose Effectiveness:

• Reduction Process for Iron/Manganese

Dissolution is/are not the target mineral(s)

• Pumping Component(s) Failure
• Well Screen/Gravel Pack Compromise
• Biofilm/Bio-Fouling Build-up
• Generally Associated with Excessive Fe & Mn

Concentrations

What is Biofilm?

A biofilm is made up of aggregates of microorganisms, such as bacteria, fungi, diatoms, protozoa, algae and any exogenous materials, which are embedded in a hydrated extracellular matrix and attached to a solid surface (well screen, pipes, ship’s hull, teeth, lungs, etc)

Young Seo, 2012. “Biofilm Formation and Control in Drinking Water Distribution Systems”

Examples of Biofilm:

Biofilm Formation on Well Pump

Iron–oxidizing bacteria use oxygen (when de-oxygenated water reaches a source of oxygen) and convert soluble ferrous iron back into an insoluble reddish precipitate of ferric iron

Thiobacillus ferrooxidans & Leptospirillum ferrooxidans

Biofilm Matrix

Biofilm Formation

Biofilm Formation in Water

Enhanced Treatment Techniques for Biofilm Elimination:

• Proprietary Blends:
• Pantonitetm PM77 (NSF 60 certified - complex mixture)
• Johnson – NU 310/400, etc….
• Cotey Dry Acid/Liquid Descaler
• Laval Boresaver BLS
• Bariod AquaClear AE
• Wire Charge Methods:
• Sonar-Jet
• Shock Blast
• Prima Cord

Enhanced Treatment Techniques for Biofilm Elimination (continued):

• Fluid Precussive Methods:
• Airburst
• Airshock
• Nitroburst/Nitro-pulse
• Jetting
• CO2 Injection:
• COMBINATION of physical and chemical!

Enhance Redevelopment Needed -When:

• Other typical methods fail and/or:

– Video taping of bore hole finds no structural failure – Pump components intact – Chronic Total Coliform Bacteria problem and/or background bacteria presence (if membrane filtration TC testing methodology utilized). – Excessive Heterotrophic Bacteria counts when plated on agar media.

Biofilm Analysis Methods:

• Advanced Laboratory Methods:
• Electron Microscopy:
• Immunofluorescence Microscopy:

» MPN Testing

• Field Analyses:
• Biological Activity Reaction Analysis (BART Assay)
• Adenosine Triphosphate Analysis (ATP Assay)

Biological Activity Reaction Analysis (BART)

• A simple yet effective method for monitoring the population size and/or activity of

specific groups of bacteria. Results are obtained by observation after 2-8 days of room temperature incubation.

• With BART, you can monitor for Iron Related Bacteria (IRB), Sulfate Reducing

Bacteria (SRB) and Heterotrophic Aerobic Bacteria (HAB) - the three most important agents involved in biofouling:

Adenosine Triphosphate Analysis (ATP)

• ATP is a molecule found in and around living cells, and as such

it gives a direct measure of biological concentration and

• health. ATP is quantified by measuring the light produced

through its reaction with the naturally

• ccurring firefly enzyme luciferase using a luminometer. The

amount of light produced is directly proportional to the amount of ATP present in the sample.

Conclusions:

• IF: Well Yield and Specific Capacity are

Decreasing &/or there is an increase in Chronic Microorganism Concentrations &

– Typical Acid Redevelopment Has Lost Its Effectiveness &/or – Well Mechanical and Physical Components are Intact:

• TIME FOR an ENHANCE REDEVELOPMENT

APPROACH !

Acknowledgements