Pilot Systems

Deciding on how to treat a new water or waste source can be very challenging. What are the solutions?

Piloting is the process of analyzing existing data, then designing a small scale test plant or multiple plants that will provide cost and operational details so that planning for a full scale plant can proceed.

Piloting is especially useful as a cost effective method of designing water or waste treatment plants where difficult water exists. When piloting is not required is when a series of detailed water analysis taken over a few years are conclusive as to the treatment method.

Piloting IS required when there is no detailed water analysis, when the analysis was not done during freshet or summer heat, when operations and maintenance data is needed, or the water analysis does not clearly indicate one treatment method or another OR multiple water sources are used, ie ground water and surface water, or multiple wells (blending).

Piloting Goals

When designing a pilot treatment plant you will need to:

gather information on pre-filtration, dosing rates and filtration alternatives
determine the operational characteristics of membrane systems
compare the performance of RO membranes supplied by different manufacturers
verify disinfection operational performance
obtain data to predict operational costs of a full scale plant

Pilot Plant Design

The pilot equipment needs to be scalable up to the eventual drinking water flow rate required. A flow rate of 0.1 to 2.0 percent of plant design is normal. The pilot should represent reality as close as possible.

Typical Types of Pilots and Frequency

Filtration:

It is important to select the right water treatment technology for the specific water available at a site. If nano-filtration can be used rather than reverse osmosis, capital costs and pumping/power costs will be reduced. Testing out disinfection technologies — ultraviolet as primary disinfection, advanced oxidation and chlorination as residual disinfection — will show if the filtration selected has improved the turbidity and UVT enough.

Data Collection Membranes

A full water sampling and analysis is required. On site sampling is normally carried out through analog signals or every 4-8 hours to obtain:

Raw and treated water pH
raw and treated water turbidity
raw and treated water iron and manganese content
raw and treated water hardness
flow consistency and consistent pressure trends

The water analysis reveals:

Major and minor contaminants
Potable or process water quality objectives
Flow rate – peak and average
Project budgets
Future expansion possibilities

Costs associated with piloting?

The cost can range from $3500 to $250,000. A pilot system can be rented or owned depending on the length of piloting time; pilots can be over 1 month or several years.

(BI pilot case study eg)

The challenges of pilots and designing treatment systems is typically there is 1) a lack of data for new water sources. 2) A few chemical analyses do not necessarily define a water source. 3) Piloting a source helps to define and log trends in water quality.

Without understanding the water chemistry or trending over an extended period of time it is difficult to optimize a water treatment design

BI Pure Water designs pilot systems all the time for our final treatment plants and has a wide variety of systems available to rent.

For the Columbia Valley a small filtration plant was pilot tested a few years ago to determine O&M cost, UV and chlorine disinfection. The results during spring melt showed raw water quality remained acceptable for self cleaning and cartridge filtration. Enough data was collected in the testing to design for a full-scale plant, and showed that the system design was cost effective and met CDW guidelines.

However when the same pilot was moved to another location three hours away to Windemere Lake, the 1 micron absolute filters became plugged every 6 days and the water quality objective of less than 1 NTU couldn’t be consistently met. It was found that the piloted equipment was wrong for that source: it was too expensive to operate and didn’t consistently conform to Canadian Drinking water turbidity guidelines. The next step was to pilot a different technology. (Then what happened)

Piloting a new water source

Water was acquired from three different wells with differing water quality. Results from the water analysis demonstrated what pressure to run the membranes at, how effective an anti-scalent can be, what type of membrane works the best, and what the treated water anfter membrane treatment would look like. (In another example?) Pilot testing was carried out with a small ultra filtration plant with Membrane A. Results showed the ultrafiltration membrane effectively removed small particle (diatoms) that were plugging the previous cartridge filter pilot, without having to use acid or caustic; this was an important O&M detail. It was also demonstrated that whether the water source was from Williston Lake or ground water, with differing chemistry, the technology could meet performance goals over the long term. The pilot also determined what the flux rate was going to be for the full-scale ultrafiltration plant.

Reverse Osmosis Pilot Test

In another pilot, Bi Pure Water tested three manufacturers of Reverse Osmosis equipment to determine the most efficient for a water source. A 5 USGPM pilot was employed with full pre-treatment and clean-in-place capability. The test was carried out over one or two years and three water sources with very different chemistry. The goals of the pilot were also to determine the best chemicals to clean with, how often RO needs to be cleaned, and ultimately the best product-to-reject ratios, for longer runs between cleaning, as well as whose technology or design is better for the source.

For a very challenging water source (where/what?), a larger mobile pilot in a 10 foot container was employed. In warm July and August months the 1 micron absolute cartridge filter was fouled by algae growth. It seemed the RO technology was too expensive on consumables and didn’t effectively reduce TOCs. Data was provided for design of alternate slow sand filtration system.

Summary:

Piloting is not required for most water sources.
If water quality falls on the borderline between clearly defined treatment technologies, significant money can be saved by piloting.
Consumable and operational costs will be better known after piloting.
Understanding if an operator is comfortable with the technology and is able to effectively operate the plant is critical at piloting stage.
The pilot demonstrates if the technology chosen can work and/or meet long-term monetary requirements