Does your water treatment system include organics removal to prevent chlorine byproducts?

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Does your water treatment system include organics removal to prevent chlorine byproducts?

“We’re not seeing all engineering consultants providing new water system designs that address organics before disinfection systems, such as chlorination and UV, and I’m concerned about it,” says BI Pure Water’s Engineering Manager, Paul Anderson. “Frankly I wouldn’t drink the water if the THMs were over 25 ppb.”

chlorine byproducts formationChlorine byproducts such as THMs (all are called TTHMs), and haloacetic acids (HAA) are formed when chlorine interacts with naturally occuring organic matter in the source water. “There are serious negative health effects with long term exposure to these disinfection byproducts. The City of Vancouver is concerned enough to lower their THMs to 25 ppb. The EPA has lowered the Stage 1 Disinfectants and Disinfection Byproducts Rule to regulate total trihalomethanes (TTHM) at a maximum allowable annual average level of 80 parts per billion (µg/L) from 100 ppb.”

“The water quality of communities, which they should have published on their websites, should indicate THMs well below the max, and we’re not seeing that. The public must demand good water treatment.”

Some UVs may even increase the problem of disinfection byproducts by breaking organic material into smaller particles with more surface area that results in even higher THMs.

BI Pure water’s senior engineer, George Thorpe, who watches the EPA studies, notes that research underway is showing that there are many more disinfection byproducts than are currently known, and long term studies on human health are underway.

Water treatment on wheels

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Water treatment on wheels

Move them anywhere for piloting or emergency potable water sources

Flexible water treatment systems are built inside mobile trailers and can be customized for the water source.

  • Treating from 10 to 60 USGPM (up to 227 liters per minute)
  • Designed to be easy to maintain
  • Pilot test for the most efficient treatment for your water source

Inside a treatment plant trailer:

  • Optional ultrafiltration for muddy/ turbid waters < 0.1 micron
  • Optional activated carbon filters for improving taste and odour, and removimg organics and potential byproducts of chlorination
  • Various sizes of filtration technologies from 200 microns down to 1 micron absolute.
  • An ion exchange unit
  • UV and/or chlorination systems for disinfection

When to use a pilot system

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When to use a pilot treatment system

A small ultrafiltration plant is tested on turbid source water

Deciding on how to treat a new water or waste source can be very challenging. Piloting, or employing a small-scale test plant, gives you system, cost and operational details that prove the concept of the full scale system.

While not being required for most water sources, piloting will:

  • save significant money if water quality falls on the borderline between clearly defined treatment technologies
  • provide info on consumable and operational costs
  • demonstrate if an operator is comfortable with the technology and is able to effectively operate the plant
  • show if the technology chosen can work and/or meet long-term monetary requirements

Piloting is especially useful:

  • Where difficult water exists,
  • 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
  • The water analysis does not clearly indicate one treatment method or another
  • When multiple water sources are used, ie ground water and surface water, or multiple wells (blending).

When piloting IS NOT required is when a series of detailed water analyses taken over a few years are conclusive as to the treatment method.

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

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: A full water sampling and analysis program is required. On site sampling is normally carried out manually 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:

A typical small pilot plant which will determine O&M cost, UV and chlorine disinfection efficacy
  • 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.

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.

Case Study 1: Pilot test shows different results at two nearby sources

A 5 USGPM pilot was employed with full pre-treatment and clean-in-place capability.

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 Canadian Drinking Water (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 CDW turbidity guidelines. The next step was to pilot a different technology.

Step 2: Testing an ultrafiltration membrane on the water source

Pilot testing was carried out to determine the efficacy of different ultrafiltration membranes. 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.

Case Study 2: Reverse Osmosis Pilot Test

RO pilot system in 10 ft container
In another pilot, BI Pure Water tested three manufacturers’ reverse osmosis membranes 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 the RO needed to be cleaned, and ultimately the best product-to-reject ratios, for longer runs between cleaning, and to determine which technology or product would be better for the source.

Case Study 3: Larger pilot plant prevents large scale errors in system design

For a very challenging water source, 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. But the data provided for the design of the alternate slow sand filtration system, saving money and time in the final system.

Tablet chlorine: safer and simpler for operators to use

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Tablet chlorine: safer and simpler for operators to use

Accutab Blue Pails

The Accu-Tab solid form of chlorine offers safety and low maintenance benefits together with a small capital investment. With no chlorine gas cylinders to handle, chlorine releases are non existent. Process safety management and risk management program compliance worries disappear.

Accu-Tab 3-inch calcium hypochlorite tablets are easy to handle and store. The chlorinators contain no moving parts or small openings to clog, keeping maintenance at a minimum. The Accu-Tab system is accurate and predictable, as easy to adjust as gas, and more consistent than bleach. BIP/Accu-Tab chlorinators are certified NSF Standard 61.

AccuTab System Bleach Gas
Safety Easy to handle, no spills Spill and leak concerns if near skin or eyes Major gas leak concerns; deadly when inhaled
Changing Chemical Easy to add tablets, only one person needed Hard to maneuver, heavy drums or lots of small carboys Two trained persons needed, breathing protection required?
Material Compability More neutral pH, less corrosive High pH, corrosive Low pH, very corrosive
Convenience 55-lb pail of tablets is easy to handle Bleach drums are awkward to handle Hard to maneuver cylinders, special handling trianing needed
Maintains Chlorine Strength Small change over a year Significant loss in a week of hot weather Consistently 100% chlorine
Chlorine Delivery Control Consistent strength makes for easy, reliable control Ever changing strength makes for control difficulty Troublesome regulators needed, harder to automate
Storage Convenience 55-lb pails stacked three high, same space as 150 lb cylinder, no separate room Drums or bulk tanks require space and possibly containment pad Separate room with special access needed, fans, scrubbers
Auxiliary Equipment No moving parts in chlorinator itself Troublesome metering pumps required Eductors, regulators have small orifices prone to plugging
Accutab Blue Pails

BI Pure Water manufactures, installs, and services an Accu-Tab chlorination system with a small footprint. In most cases the system can be installed by in-house staff in less than a day.

A word about chlorine chemistry

Accutab Blue Pails

Accu-Tab tablets are available for Potable / Industrial Water Treatment (white) and Commercial Swimming Pools (blue). Product available in 25 kg containers.

Chlorine is available in many different forms. The most common include gas, liquid chlorine (sodium hypochlorite or bleach) and solid calcium hypochlorite. All three forms generate hypochlorous acid – the germ-killing form of chlorine – when dissolved in water. Chlorine is the only chemical that provides residual protection, which is very important and required in many water treatment applications.

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New AOP - Biperliminate addresses the toughest pollutants in the environment, pilot experiment https://t.co/HoiW4QQOUd via @YouTube

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