water treatment plant selection by manitoba hydro for … · water quality source and the...

Manitoba Hydro Case Study January 2018

Water Treatment Plant Selection by Manitoba Hydro for the

Lower Nelson River Stations

Case Study

Dr. Lyle Henson Membrane Specialists

Isaac Deluna Manitoba Hydro


ABSTRACT

The old water treatment systems at the LNRS were not able to meet Manitoba Regulations and

Guidelines for Canadian Drinking Water Quality (GCDWQ) and a decision was made to seek viable

options as a replacement. Manitoba Hydro performed a series of pilots utilizing Microfiltration,

Ultrafiltration and Nanofiltration (Fyne Process) to evaluate the technologies for potential use at these

facilities to meet their potable water needs. In addition to these technologies water hauling was

evaluated as a potential means to meet their needs.

Microfiltration and Ultrafiltration were eliminated as the pilots produced water which did not meet the

Manitoba Regulation and Guidelines for Canadian Drinking Water Quality (GCDWQ). Additionally, both

technologies were shown to require excessive operations and maintenance due to the nature of the raw

water quality source and the pretreatment required with these technologies. The Nanofiltration (Fyne

Process) was successful as it exceeded the GCDWQ and was shown to be an essentially “hands off”

technology in terms of operation.

Nanofiltration (Fyne Process) was then evaluated against water hauling and it was determined it was the

preferred choice due to a higher NPV, no risk of cross contamination, low operator certification

requirement, no supply risk due to weather and the inability of the local municipality to meet current

regulatory requirements.


Water Treatment Systems at the Lower Nelson River Stations (LNRS)

Hydroelectric generating stations are typically remote in nature and operated by a small number of

operation and maintenance personnel. The current population of the Lower Nelson River Stations

(LNRS) fluctuates between 20 to 25 people during the day shift and 2 to 3 people during the night shift.

The population during heavy maintenance periods (spring and fall) have been estimated to be between

25-30 people during the day shift and 15-20 during the night shift.

The original water treatment systems at the LNRS were fed from the station service and cooling water

system carrying Nelson River water from the forebay through the turbine unit main strainer to a

hydropneumatic tank. Historically, prior to entering the hydropneumatic store tank raw water was

dosed with chlorine. From the hydropneumatic store tank, the “treated” water was then distributed

through the generating station.

For years this process was the water treatment system at Limestone Generating Station and Long Spruce

Generating Station for production of potable water. A multimedia filtration system was also in operation

at Kettle Generating Station during this time for potable water production. The old water treatment

systems at the three stations were not able to meet Manitoba Regulation and Guidelines for Canadian

Drinking Water Quality (GCDWQ) and a decision was made to seek viable options as a replacement.

Additionally, consideration for the remote nature of these facilities and the limited availability of

operations personnel had to be considered when choosing the appropriate technology for use.

Water Treatment Alternatives Considered

The water quality data gather by Manitoba Hydro indicates that the Nelson River contains high levels of

turbidity (up to 60 NTU) and dissolved components. Research indicates that turbidity levels at 30 NTU or

higher significantly decrease the effectiveness of chlorination in the treated water, which creates a high-

risk of microbiological contaminants in the drinking water. Surface water (Nelson River Water) typically

contains high levels of dissolved organic matter, and when mixed with chlorine, it creates by-products

such as Trihalomethanes (THMs) and Haloacetic Acids (HAA) which are considered carcinogenic. Typical

analytical results for the Nelson River are shown in Table 1 below.

Various water treatment technologies were considered for the upgrade of the water treatment systems

at the LNRS, with the following four alternatives being the most viable.

• Water Hauling

• Microfiltration System

• Ultra filtration System (UF)

• Nanofiltration System (Tubular Membranes)


Water Hauling

The first option considered was hauling treated water by truck to the generating station. Depending on the water usage at the generating station, water could be delivered as required. There are advantages with this alternative regarding the permitting, operator classification and operation and maintenance requirements. Classification and permitting would only be required for the distribution system (level 1) and minimum chemicals would be required. On the other hand, there are huge disadvantages with this alternative. First, the potential of cross contamination when handling the water from the water plant to the point of use is a serious concern. Second, the cost of transporting water is high considering the purchased/leasing of trucks, maintenance, and garage. Finally, the process is vulnerable to delays in water delivery due to weather conditions,

Table 1 - Lab Results – RAW WATER (SUMMARY)

Sample Date Comments

Parameter Units Mar-27

2014

April-10

2014

May-01

2014

May-21

2014

Jun-11

2014

Jun-13

2014 Pass/fail

Dissolved Organic

Carbon (C)

mg/L 8.12 - 37.0 - - 8.03

Alkalinity (Total as

CaCO3)

mg/L 120 - 112 - - 90.0

Total Organic

Carbon (C)

mg/L 9.08 - 8.55 - - 8.58

pH pH 7.9 8.21 8.12 8.19 19 8.21

Total Inorganic

Carbon (C)

mg/L 28.8 - 28.5 - - 23.6

True Colour TCU 11 14 7 13 - 23

Total Dissolved

Solids

mg/L 192 - 184 - - 174

Turbidity NTU 10 9.7 8.9 9.8 16 18

Total Aluminum

(Al)

μg/L 464 403 414 438 435 547

Total Iron (Fe) μg/L 455 412 404 522 633 722

Total Lead (Pb) μg/L 0.27 0.29 0.24 0.29 0.27 0.31

Total

Trihalomethanes

μg/L <1.0 - 180 - - 450

Total Haloacetic

Acids

μg/L <5.0 - - - - -

THM Formation

Potential

μg/L - - - - - 460

E. coli (QT) MPN/100mL 11 - 0 - - 0

Total Coliforms

(QT)

MPN/100mL 48 - 0 - - 2


truck breakdowns, and truck operator availability. The Town of Gillam is a remote location where the closest city/town is 300 Km away and it is the only source of water when considering this option. Preliminary engineering draft assessment conducted by a consultant indicated that the Town of Gillam water treatment plant could not handle any additional load unless upgrades were made to the water treatment process and infrastructure. In addition, the pressure filters at the Town of Gillam water treatment plant are currently not meeting standards (turbidity).

Micro Filtration

This alternative produces higher levels of water quality than more traditional methods of coagulation and filtration (conventional treatment systems) and will typically meet or exceed current water quality regulations. One of the major drawbacks of this system is that the raw water requires pre-treatment (reduce dissolved organics) prior to being fed to the primary system (microfiltration). If the system is installed without pre-treatment there is a high chance that turbidity and particulate content of the raw water will cause membrane fouling, frequent cleaning cycles, higher operator involvement and increase pathogens. Because of the pre-treatment required, this alternative presented huge disadvantages such as high capital cost, a larger footprint because of the two-stage treatment, associated chemical costs and a higher operator classification level. As part of the Water Treatment Plant (WTP) upgrades at Lower Nelson River Stations a study was conducted at Henday Converter Station to prove the viability of installing a microfiltration water treatment system without pre-treatment. Two water quality tests were performed at Henday and in one of the tests, the treated water showed non-compliance with the Total Trihalomethanes parameter mandated by MR 41/2007. Also, it was determined that DOC removal was poor with this technology. Table 2A below contains the overview of the non-compliant results.

The main disadvantages of the water hauling option are:

• Lower NPV than nanofiltration Fyne Process® system

• No self-sustaining potable water source at each station in case of emergency

• The potential of cross contamination

• Possibility of delays in water delivery due to adverse weather and/or road conditions

• Truck breakdowns

• Truck operator availability


Table 2A – MF Pilot Study at Henday Converter Study Results

Pilot Plant (Ultra Filtration/Hollow Fiber) With this technology raw water is pumped through a coarse filter (50 & 100 micron), then the water coming out of the cartridge filter passes through a ultrafiltration (UF) membrane unit. The product water coming out of the UF membranes is directed to the post UF water storage tank. The Ultrafiltration membranes are back washed periodically to avoid differential pressure increase. A chlorination system is provided for injection into the back wash water entering the UF membranes. The back-wash water coming out of the membranes is collected in a wash water tank and then disposed of slowly. The filtered water is then injected with antiscalant solution for control of scale on the surface of the membranes. A booster pump feeds the water into two housings of Ultrafiltration membranes. While passing through the membranes water divides into three streams – product, reject and recycle water going back to the Ultrafiltration pump.

A pilot plant was installed at Limestone Generating Station in 2016 to determine if this technology was

suitable for use at the LNRS. The pilot plant resulted in the following findings:

• The 50-micron filters constantly plugged up (every second day), requiring operator intervention.

These filters were located downstream from the raw water supply. Note, new filters would need

to be purchased and installed. This negatively impacted the operation and maintenance cost of

the proposed system. Figure 1 and Figure 2 shows the condition of the 100-micron particle

filters plugged and requiring operator intervention.

• The UF system frequently stopped due to high differential pressure at the 50-micron filters. The

pilot plant could not run for more than 1/2 day without operator intervention.


• This technology required the use of antiscalant (chemical product) prior to UF. As water is

produced, this antiscalant need to be replenished which adds another cost to the operation.

This antiscalant has been approved by the Regulator, BUT it still has a negative impact to the

environment.

Figure 1 – Fouled 100 Micron Particulate Filters (UF Pilot Plant at Limestone)


Figure 2 – Fouled 100 Micron Particulate Filters (UF Pilot Plant at Limestone)

Pilot Plant (Nanofiltration/Fyne Process)

A small nanofiltration pilot plant was installed at Limestone Generating Station and Radisson Converter Station in 2014. A small Mini-Fyne Pilot Unit was used for the pilot tests fitted with three full scale 12 ft C10 modules each containing a different membrane to be tested (AFC30, AFC31 & ES404). The pilot plant is shown in the Figure 3 below.

Figure 3 – Fyne Tubular Nanofiltration Membrane Pilot at Limestone LNRS


The semi-permeable Nanofiltration membrane is coated on the inside of the membrane tubes. The membrane tubes are connected by “U”-shaped connectors in a series flow path within each module. Cut-Away photographs of the module follow showing the end connections and internal tube arrangement are shown in Figure 4 below.

Figure 4 – C10 Cutaway View

There is only one inlet and one outlet connection on each module for raw water. A ½” diameter foam ball is fitted in one of the raw water connections on each module. A screened “foam ball catcher” at each end of the flow path keeps the foam ball from leaving the system. During operation, flow reversal causes the foam ball to pass through all the tubes in the module before being caught in the foam ball catcher at the other end of the module providing cleaning of the inside wall of the membrane tube.

A pressurized feed of raw water was supplied to the unit for the pilot. The Mini-Fyne unit has a higher-p r e s s u r e recirculation pump, driven by a variable frequency drive, to provide the correct flow conditions at the membrane surface for process and foam ball clean.

When the unit is filtering, raw water is circulated at pressure by a recirculation pump through the inside of the membrane tubes. Additional raw water is drawn into the recirculation loop. Clean filtered water passes through the membrane tube wall and is collected in the module shroud.

The concentration of organics and other contaminants slowly builds up in the recirculation loop and periodically this water is discharged to waste in a flush cycle. In the flush cycle the recirculation pump was slowed down and the reject by-pass valve was opened. The frequency of opening of the valve controls the recovery (percentage for raw water converted to filtered water).

During the filtration process, the inside walls of the membrane tubes slowly become coated with contaminants from the raw water. To maintain cleanliness of the membrane surface and to discharge the concentrated raw water contained in the recirculation loop, the unit periodically and automatically performed a “foam ball clean”. During the foam ball clean, the direction of the flow of the raw water in the module is reversed. This causes the foam ball to pass through each of the 72 membrane tubes inside the module, cleaning the inside surface of the membrane tube, while at the same time the reject valve opens discharging the concentrated raw water and drawing fresh water into the recirculation loop. The foam ball clean occurred every six flush cycles.

For the pilots the C10 modules were fitted with PCI type AFC30, AFC31 & ES404 membranes. These membranes are manufactured from polyamide (AFC30 & AFC31 75% retention of CaCl2) and


polyethersulphone (ES404 4000 MWCO) material.

The unit is automatically controlled by a programmable relay controller to undergo automated foam ball cleaning cycles on a pre-set frequency. A VFD driven recirculation pump draws water into the recirculation loop and filtrate leaves the system through a permeate flow meters. The recirculation loop water becomes more concentrated over time and is purged to drain each foam ball cycle. The foam ball interval setting controls the operating recovery.

The pilot plant resulted in the following:

• High quality water that exceeds Manitoba Regulation and Guidelines for Canadian Drinking

Water Quality as indicated in Table 2B below

• Low operation and maintenance requirements, essentially “hands off” operation

• No chemical required for treatment

• Chemical cleaning extended to 3-4 months due to mechanical foam ball clean

• Superb color removal as shown in Figure 5 and Figure 6

• Outstanding turbidity removal as shown in Figure 7

• Smaller foot print

• Easy installation

Figure 5 – Raw Water at Radisson Converter Station


Figure 6 – Finished Water at Radisson

Figure 7 – Finished Water Turbidity Results at Limestone


PILOT PLANT @ LIMESTONE G.S - LAB RESULTS SUMMARY

TABLE 2

Lab Results – AFC-30 membrane (SUMMARY)

Sample Date Comments

Parameter Units Mar-27

2014

Apr-10

2014

May-01

2014

May-21

2014

Jun-11

2014

Jun-13

2014

Pass/fail

Dissolved Organic

Carbon (C)

mg/L 0.89 - 0.73 - - 0.68 Pass

Alkalinity (Total as

CaCO3)

mg/L 65 - 75.2 - - 81.9 Pass

Total Organic

Carbon (C)

mg/L <0.50 - 0.54 - - < 0.50 Pass

pH pH 7.7 8.03 8.01 8.15 8.0 8.19 Pass

Total Inorganic

Carbon (C)

mg/L 16.4 - 19.7 - - 19.2 Pass

True Colour TCU 7 < 5 < 5 < 5 < 5 12 Pass

Total Dissolved

Solids

mg/L 104 - 116 - - 106 Pass

Turbidity NTU 0.1 < 0.1 < 0.1 0.1 < 0.1 < 0.1 Pass

Total Aluminum

(Al)

μg/L 4.7 < 3.0 3.4 < 3.0 < 3.0 3.4 Pass

Total Iron (Fe) μg/L < 10 < 10 < 10 < 10 < 10 < 10 Pass

Total Lead (Pb) μg/L < 0.20 < 0.2 < 0.20 < 0.20 < 0.20 < 0.20 Pass

Total

Trihalomethanes

μg/L 16 - 44 - - 29 Pass

Total Haloacetic

Acids

μg/L 6.8 - - - - - Pass

THM Formation

Potential

μg/L _ - - - - 29 Pass

E. coli (QT) MPN/100mL 0 - 0 - - 0 Pass

Total Coliforms

(QT)

MPN/100mL 0 - 0 - - 0 Pass


The results conclusively showed that the AFC30 membrane exceeded the CDWS and would meet the needs of both the Limestone, Long Spruce, Kettle and Radisson facilities. Additionally, the unit proved to be largely hands off and require a minimum amount of manpower to operate. There was only a single clean performed during the pilot and this was prior to start-up at the Radisson facility. As anticipated the pilot confirmed the need to perform a chemical clean every 3 or 4 months due to the efficacy of the foam ball clean. The results of both pilots supported the use of the Fyne process for all of Manitoba Hydro’s Generating Stations and HVDC facilities due to performance, limited manpower requirements and cost.

NPV Evaluation (Water Hauling vs Fyne Nanofiltration Process)

Of the four original choices to be considered only two were considered to be viable options based on

the technology assessments performed. An economic analysis comparing the two viable alternatives

(water hauling vs Fyne Nanofiltration Process®) was performed with the following results:

• Nanofiltration Fyne Process® NPV (-$4.5M) is higher than water hauling NPV (-$6.9M).

• The high capital cost of $2M for water hauling and annual operator cost of $360,000 (2-truck

drivers) makes this option not economically viable.

As a result, the Nanofiltration Fyne Process® was recommended over water hauling. A feasibility study

was developed and performed on the Fyne Nanofiltration system. Below are some of the key findings

from the study:

• Nanofiltration Fyne Process® system provides no-risk of cross-contamination; ensuring the

safety & health of the employees and the public.

• Low environmental impact and minimum operator involvement

• Lab results met Manitoba Regulation and Canadian Drinking Water Quality Guidelines.

• Low System Operator Classification (level II).

A summary of evaluation criteria used for final assessment of the technology can be found in Table 4

below.

Table 4 – Evaluation criteria used for the Fyne Pilot Plant and Final Assessment

Criteria Assessment

• Water quality to meet or exceed Manitoba Regulation

and Guidelines for Canadian Drinking Water Quality

(GCDWQ)

Lab results met Manitoba Regulation and Guidelines for

Canadian Drinking Water Quality.

• Operation and maintenance requirements Low

• Footprint requirements Small footprint required.

• Chemical usage (environment) None (only for membrane cleaning, typically every 3 months).

Low environmental impact

• Installation requirements Minimum. Plug-in type. Pilot plant was installed and

commissioned in 3 days.

• Complexity of the system Low complexity.

• System performance using Nelson River water during

the spring melt and summer months

Very good. Raw water turbidity spikes did not affect the

system performance.


Conclusion

The old water treatment systems at the LNRS were not able to meet Manitoba Regulations and

Guidelines for Canadian Drinking Water Quality (GCDWQ) and a decision was made to seek viable

options as a replacement. Manitoba Hydro performed a series of pilots utilizing Microfiltration,

Ultrafiltration and Nanofiltration (Fyne Process) to evaluate the technologies for potential use at these

facilities to meet their potable water needs. In addition to these technologies water hauling was

evaluated as a potential means to meet their needs.

Microfiltration and Ultrafiltration were eliminated as the pilots produced water which did not meet the

Manitoba Regulation and Guidelines for Canadian Drinking Water Quality (GCDWQ). Additionally, both

technologies were shown to require excessive operations and maintenance due to the nature of the raw

water quality source and the pretreatment required with these technologies. The Nanofiltration (Fyne

Process) was successful as it exceeded the GCDWQ and was shown to be an essentially “hands off”

technology in terms of operation.

Nanofiltration (Fyne Process) was then evaluated against water hauling and it was determined it was the

preferred choice due to a higher NPV, no risk of cross contamination, low operator certification

requirement, no supply risk due to weather and the inability of the local municipality to meet current

regulatory requirements.

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