Summary of the Electrocoagulation Treatment of Municipal Waste Water

Background

F&T Water Solutions conducted a series of tests at a Municipal Water Treatment center in Connecticut. The present capacity of this municipal water treatment facility is approximately 7 million gallons/day. F&T Water Solutions, LLC sent an F&T mobile 10 gpm Electrocoagulation (EC) unit (self contained in a 16 ft mobile trailer) to the central municipal water treatment facility in Connecticut and conducted a series of test runs over a week long period from October 1-7, 1014. The Water Pollution Control Authority main goals were to reduce the amount of ammonia (nitrogen) and phosphorus. A series of Electrocoagulation treatments were conducted on the water with various anodes/cathodes, and power settings and configurations using flowrates in the 1.5 - 6.7 gpm range. The pH of the untreated water is typically measured at approximately 6.9-7.2.


Goals

Treatment goals included the reduction of these contaminants:

  1. Ammonia (Nitrogen)
  2. Phosphorus
  3. TSS (Total Suspended Solids)
  4. Copper
  5. Zinc

Results

Testing was conducted over a weeklong period from October 1-7, 2014. The majority of the laboratory testing was conducted by the Water Pollution Control Authority onsite laboratory facility. Additional testing for the metals (copper and zinc), as well as additional testing for total phosphorus was conducted by the University of Connecticut (UCONN) Center for Environmental Sciences and Engineering laboratory. There are some inconsistencies with the total phosphorus results generated by each laboratory with the results from the UCONN laboratory being considerably lower than those generated by the laboratory.

A summary of all laboratory results is attached to this report –see “Appendix A - Summary of F&T Water Solutions, LLC Testing Trials.

A series of test runs conducted over a 3 day period (Oct 1-3/14) was conducted using Aluminum plates as the sacrificial electrode material. This was followed by an additional 3 day period (Oct 4-7/14) when Iron plates were used as the sacrificial electrode material.

Ammonia (Nitrogen)

F&T’s Electrocoagulation can be used to reduce ammonia although low flow rates are generally required to give adequate reaction time to occur in the reaction chamber. No laboratory testing was conducted for during the trials for ammonia and other nitrogen containing compounds (ie nitrate, nitrite, etc).

It should be noted that there are a number of highly effective secondary processes that have been effectively used with electro-coagulation systems to reduce nitrogen containing contaminants (i.e. aeration, biofilters, etc).

Phosphorus

Electrocoagulation is very effective at removing phosphate/phosphorus. The total phosphorus concentrations appear to have had a fairly wide range over the 7 days of testing. According to the data from the lab the raw (pretreated) water total phosphorus concentrations ranged from 0.27 – 0.51 mg/L. The data from the University of Connecticut laboratory showed a result of 0.100 for the raw (pretreated) water.

Using the data from the laboratory the results vary widely but are generally in the range of 60-80% reduction of total phosphorus. It should be noted that the data from Oct 6/14, the results for the treated samples are higher than that of the raw sample – this is perplexing but indicative of analytical testing error as the F&T Electrocoagulation system cannot make phosphorus/phosphate and cause an actual increase in the total phosphorus concentration. Although the data from the University of Connecticut laboratory is considerably lower than the data from the laboratory, the trend is similar. Table 1- Total Phosphorus in Wastewater shows that the raw sample total phosphorus concentration was 0.100 mg/L and of the 9 treated samples that were analyzed all of them had total phosphorus concentrations in the range of 0.012 – 0.024 mg/L, reductions of total P in the range of between 76-88%. The total P from the University of Connecticut laboratory results are shown in Table 1 – Total Phosphorus in Wastewater. The average % removal of the total phosphorus based on this set of results was 83.3%.

Table - 1 Total Phosphorus in Connecticut Wastewater
Sample # Type of Sample Total Phosphorus Concentration (mg/L) % Reduction
1 Raw (untreated) 0.100 N/A
2 Treated (Fe plates) 0.018 >82.0
3 Treated (Fe plates) 0.016 84.0
4 Treated (Fe plates) 0.013 87.0
5 Treated (Fe plates) 0.024 76.0
6 Treated (Fe plates) 0.019 81.0
7 Treated (Fe plates) 0.017 83.0
8 Treated (Fe plates) 0.012 88.0
9 Treated (Fe plates) 0.017 83.0
10 Treated (Fe plates) 0.015 85.0

F&T’s Electrocoagulation was very successful in removing phosphorus during the trials, which is consistent with results that have been observed in past trials using the EC technology.

TSS (Total Suspended Solids)

Treatment with Electrocoagulation is very successful at removing Total Suspended Solids (TSS) by allowing the solids to be removed with the floc that is formed during the treatment process. Although no TSS analysis were completed during the trials, historical data has shown that TSS removal rates of 95% or higher are not uncommon. The suspended solids will be removed with the floc using a process such as Clarification, Dissolved Air Flotation (DAF) or a wide variety of other secondary settling processes.

Metals (Copper, Zinc)

Traditionally, electrocoaguation processes such as F&T’s system have been very successful at removing dissolved metals. The University of Connecticut laboratory performed the analytical testing for copper and zinc on a series of 10 samples that were submitted for testing. The results of that testing are shown in Table 2 – Copper and Zinc Results for Connecticut Wastewater.

Table 2 – Copper and Zinc Results for Connecticut Wastewater
Sample# Sample Type Copper (ug/L) % Removal Zinc (ug/L) % Reduction
1 Raw (untreated) 7.0 63.6
2 Treated 12.2 N/A 24.7 61.2
3 Treated 13.4 N/A 36.6 42.5
4 Treated 11.8 N/A 35.5 44.3
5 Treated 12.2 N/A 32.3 49.2
6 Treated 12.2 N/A 30.6 51.9
7 Treated 7.9 N/A 30.8 51.6
8 Treated 8.2 N/A 11.7 81.6
9 Treated 9.4 N/A 22.3 64.9
10 Treated 8.5 N/A 29.2 54.1

It appears from the analytical result report from the University of Connecticut laboratory that the metals were run on a total metals basis rather than a dissolved basis. This is very problematic as during the treatment the dissolved metals are precipitated out with the floc that is created. The analytical test must be run with the floc removed (ie analyzed on a dissolved basis), otherwise the metals that are removed (into the floc) are included in the final metals result. That being the case, all of the results for the copper and zinc testing for the treated samples should essentially be the same as the results for the Raw or untreated sample. The samples should be reanalyzed on a dissolved basis to generate useful data.

Bacteria

Although bacteria reduction was not included as one of the goals of the treatment, it should be noted that EC is an excellent process for bacteria eradication. The bacteria eradication is non selective so must be used at a location in the process where desirable bacteria is not negatively affected. The laboratory did conduct some analyses of the fecal coliform concentration on a small series of the samples taken during the trials. The data is shown in Table 3 – Fecal Coliform Concentration in Connecticut Wastewater.

Table 3 – Fecal Coliform Concentration in Connecticut Wastewater
Date Sample Number Type of Sample Fecal Coliform (colony/100 mL) % Removal
2014-10-06 1 Raw (untreated) >2419.6
2014-10-06 4 Treated 488 >79.8
2014-10-06 9 Treated 137 >94.3
2014-10-07 15 Treated 921 >61.9
2014-10-07 1 Raw (untreated) >2419.6
2014-10-07 2 Treated 30 >98.7
2014-10-07 3 Treated 72 >97.0
2014-10-07 8 Treated 0 >99.9
2014-10-07 9 Treated 12 >99.5
2014-10-07 10 Treated 43 >98.2

Summary

The F&T EC treatment demonstrated significant reduction of the total phosphorus. Both aluminum and iron electrode plates were used during the trails – the iron electrode plates performed better than the aluminum for all parameters measured. Using the data from the University of Connecticut, the best treatment achieved a result 0.012 mg/L Total P, a reduction of 88% from the original Raw (untreated) value of 0.100 mg/L. As the data shows EC is highly effective at the control of bacteria, including fecal coliforms, which is important to any municipal water processing facility.

EC is an excellent technique for removal of Total Suspended Solids (TSS) and dissolved metal removal. The trials that were run on Oct 1-7/14 were not followed by a secondary solids removal process to prove this out.

Based on the results, it is recommended to conduct a follow up pilot test using a larger flow rate with the appropriate secondary solids separation system to further prove out the efficacy of the EC process for the removal of Total P, TSS, Copper and Zinc.




Appendix A - Summary of F&T Water Solutions, LLC Testing Trials in Connecticut - October 2014

10/1/14 - Samples Run with Al Plates
WPCF Fin Eff WPCF Pre-treat EC Unit Effluent
Sample Type Comp Grab Grab Grab Grab Grab Grab Grab
Sample Number Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7
Flowrate (gpm) 1.5 2.5 3.7 4.6 5.6 6.7
Amps (A) 44 54 61 53 52 49
Volts (V) 16 16 16 16 16 16
Total P (mg/L) 0.6 0.35 0.18 0.13 0.29 0.2 0.16 0.11
Total P - % Removal 48.6 62.9 17.1 42.9 54.3 68.6
10/2/14 - Samples Run with Al Plates
WPCF
Fin Eff
WPCF
Pre-treat
EC Unit Effluent
Sample Type Comp Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab
Sample Number Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7 Sample 8 Sample 9 Sample 10
Flowrate (gpm) 1.5 2.5 3.7 4.6 5.6 6.7 1.5 3.8 6.5
Amps (A) 44 54 61 53 52 49 249 220 216
Volts (V) 16 16 16 16 16 16 50.7 55.5 55.4
Total P (mg/L) 0.42 0.4 0.14 0.15 0.17 0.15 0.31 0.39 0.15 0.13 0.11
Total P - % Removal 65.0 62.5 57.5 62.5 22.5 2.5 62.5 67.5 72.5
Fecal Coliform (colony/100 mL) 137 1986 205
10/3/14 - Samples Run with Al Plates
WPCF
Fin Eff
WPCF
Pre-treat
EC Unit Effluent
Sample Type Comp Grab Grab Grab Grab Grab Grab Grab Grab
Sample Number Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7 Sample 8
Flowrate (gpm) 1.5 2.5 3.5 4.3 5.4 3.3 2.5
Amps (A) 39 34 60 40 53 141 34
Volts (V) 16.5 16.5 16.2 16.5 16.5 56.4 16.5
Total P (mg/L) 0.51 0.33 0.22 0.23 0.13 0.16 0.12
Total P - % Removal 35.3 56.9 54.9 74.5 68.6 76.5
Fecal Coliform (colony/100 mL) 691 649 488 344 299 185 161 517
Fecal Coliform - % Removal 6.1 29.4 50.2 56.7 73.2 76.7 25.2
10/4/14 - Samples Run with Fe Plates
WPCF Fin Eff WPCF Pre-treat EC Unit Effluent
Sample Type Comp Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab
Sample Number Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7 Sample 8 Sample 9 Sample 10
Flowrate (gpm) 1.5 2.5 3.7 4.6 5.6 6.7 1.5 3.8 6.5
Amps (A) 87 86 83 83 83 81 301 301 301
Volts (V) 16.5 16.5 16.5 16.5 16.5 16.5 42.3 47.8 52.5
Total P (mg/L) 0.42 0.09 0.08 0.08 0.12 0.08 0.08 0.08 0.15 0.15
Total P - % Removal 78.6 81.0 81.0 71.4 81.0 81.0 81.0 64.3 64.3
10/6/14 - Samples Run with Fe Plates
WPCF
Fin Eff
WPCF
Pre-treat
EC Unit Effluent
Sample Type Comp Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab
Sample Number Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7 Sample 8 Sample 9 Sample 10 Sample 12 Sample 13
Flowrate (gpm) 1.5 2.4 3.5 4.4 54 6.5 1.5 3.7 6.7 6.5 6.5
Amps (A) 65 75 93 82 79 71 301 301 301 249 220
Volts (V) 16.5 16.5 16.5 16.5 16.5 16.5 41.3 48.7 52.8 28 38.8
Total P (mg/L) 0.83 0.27 0.30 0.31 0.5 0.97 2 0.23 0.25 0.25 0.25 0.3
Total P - % Removal N/A N/A N/A N/A N/A 14.8 7.4 7.4 7.4 N/A N/A
Fecal Coliform (colony/100 mL) >2419.6 488 137
Fecal Coliform - % Removal >79.8 >94.3
10/7/14 - Samples Run with Fe Plates
WPCF Fin Eff WPCF Pre-treat EC Unit Effluent
Sample Type Comp Grab Grab Grab Grab Grab Grab
Sample Number Sample 2 Sample 3 Sample 8 Sample 9 Sample 10
Flowrate (gpm) 1.5 2.5 3.5 4.4 54
Amps (A) 64 80 93 82 79
Volts (V) 16.5 16.5 16.5 16.5 16.5
Total P (mg/L) 1.82 0.46 0.17 0.32 0.25 0.2 0.14
Total P - % Removal 63.0 30.4 45.7 56.5 69.6
Fecal Coliform (colony/100 mL) >2419.6 30 72 0 12 43
Fecal Coliform - % Removal >98.7 >97.0 >99.9 >99.5 >98.2

NOTE: All Results above generated by the Water Pollution Control Authority Lab


Results from Testing Conducted at University of Connecticut (UCONN) Center for Environmental Sciences and Engineering Laboratory
WPCF
Fin Eff
WPCF
Pre-treat
EC Unit Effluent
Sample Type Grab Grab Grab Grab Grab Grab Grab Grab Grab Grab
Sample Number Sample 1 Sample 2 Sample 3 Sample 4 Sample 5 Sample 6 Sample 7 Sample 8 Sample 9 Sample 10
Flowrate (gpm) 1.5 2.4 3.7 4.5 5.7 6.5 1.4 3.8 6.5
Amps (A) 68 44 50 38 46 52 156 220 216
Volts (V) 16.1 16.1 16.1 16.1 16.1 16.1 56.1 55.5 55.4
Total P (mg/L) 0.100 0.018 0.016 0.013 0.024 0.019 0.017 0.012 0.017 0.015
Total P - % Removal 82.0 84.0 87.0 76.0 81.0 83.0 88.0 83.0 85.0
Total Copper (ug/L) 7.7 12.2 13.4 11.8 12.2 8.9 7.9 8.2 9.4 8.5
Total Copper - % Removal N/A N/A N/A N/A N/A N/A N/A N/A N/A
Total Zinc (ug/L) 63.6 24.7 36.6 35.5 32.3 30.6 30.8 11.7 22.3 29.2
Total Zinc - % Removal 61.2 42.5 44.2 49.2 51.9 51.6 81.6 64.9 54.1