Who we are?

Palintest manufactures a range of advanced water and environmental testing equipment, and from its Tyneside base exports to over 100 countries across the globe. These products are used in a wide variety of applications to protect the environment and safeguard public health. Crucially Palintest are able to simplify testing for key water quality parameters, enabling critical water quality decisions to be made with confidence.

Total Residual Oxidants (TRO)

• Guidelines across the globe
• The problems of transient species 

Portable methods:

• DPD method
• Lissamine Green B method
• Other colorimetric methods
• Amperometric Sensor 

Laboratory methods:

• Amperometric Titration
• Ion Chromatography
• Spectrophotometric method
• Iodometric titration 

Implications on DWI guidelines for TRO?

Total Residual Oxidants

Usually used in the context of chlorine dosing
Can be applied to other oxidants e.g. Chlorine Dioxide and the DBP – chlorate and chlorite
Usually in the context of drinking water

Chlorite is the primary DBP (50 – 70%) Chlorate also produced (dependent on pH conditions) Chlorite and Chlorate can be introduced by the generator Most generators use chlorite or chlorate precursor chemicals

1. Total Residual Oxidants mean ClO2, ClO2- and ClO3-

(Within the context of chlorine dioxide dosing)
(May include chlorine if chlorinated water is being treated with ClO2)

DWI Guidelines – Guideline 31

BS EN 12671: 2009 – European Standard Chemicals used for treatment of water intended for human consumption.

ClO2 and ClO2- monitored daily ClO3- monitored monthly Maximum Disinfectant Residual Levels (defined under DBPR: 2002) 0.8mg/l ClO2 1mg/l ClO2-

2. DWI requirements are relatively stringent 

ClO2 is highly volatile

• Samples should be taken in amber glassware
• Small headspace
• Minimal agitation
• Testing must be carried out on site and carefully

ClO2- and ClO3- are persistent

• More suitable for sampling and off site analysis
• Off site analysis - issues in real time decision making

3. On site analysis is the best way of complying with DWI

DPD LGB Amaranth CPR ACVK ChlordioX™ Plus

DPD method

The ‘Palin system’ Blue Book method US EPA approved method Widely accepted method, e.g. EA, HSE No longer an AWWA Standard Method (21st edition) A general oxidation method, i.e. not selective Determination of ClO2 (and ClO2- possible) ClO2- method difficult and time consuming Can result in negative values if chlorine present A ‘difference’ method Concerns over chlorite and chloride interference Removal as AWWA Standard method

4. DPD method is no longer a AWWA standard method for chlorine dioxide

Lissamine Green (LGB)

US EPA Approved method ClO2 specific ClO2- determination possible with Horseradish peroxidase (HRP)

Dye bleaching method for ClO2

• Time and temperature dependence
• Operator errors

Addition of HRP for ClO2-

• A ‘difference’ method
• Generally non-standard methods for ClO2
• Useful for process optimisation
• Not so good for regulatory reporting
• No ability to quantify ClO2- (or ClO3-)

Amaranth Method

Popular in Europe Small test range Generally interferent free Dye bleaching method

 Chlorophenol Red (CPR)  Method

• Generally interferent free (ClO2- can be an issue)

 Acid Chrome Violet K (ACVK) Method

• Generally interferent free

Dye bleaching method

• Method defined in BS EN 12671:2009 

5. Other colorimetric methods are available

6. Colorimetric methods suffers from difficulties in the field

7. Photometric dye bleaching methods can lead to operator error

•Patented Palintest technology for ClO2 and ClO2- •US EPA Approved method The ONLY portable US EPA approved method for ClO2- •Enables compliance to US EPA requirements (daily monitoring of ClO2 and ClO2-, monthly for ClO3-) •Uses standard chemistry (similar to amperometric titration method) •Not DWI (because of lack of ClO3-) •Sequential test protocol •Aims to simplify ClO2 and ClO2- determination •Can carry out chlorine measurement •ClO2- is difference method (but not reliant on user)

8. ChlordioX™ Plus enables compliance with most of DWI requirements

Phương pháp PTN  Bao gồm chuẩn độ điện tích Amperometric , Sắc ký ION, Chuẩn độ I ốt, Quang phổ

Amperometric Titration

Sequential titration method Titration with PAO or thiosulphate with pH control ClO2, chlorine (free and combined), ClO2- and ClO3- possible Requires a skilled technician (especially for ClO3-)

Ion Chromatography

The best way to determine ClO2- and ClO3- No good for ClO2 Requires specialist equipment Requires careful sample preparation Requires skilled technician

Spectrophotometry

UV/Vis (λ = 360nm) spectrophotometry can be used for ClO2 If ClO2- present, can lead to interferences from intermediate species Some manufacturers offer this as a visible region test (λ = ~420nm) Interferences more prominent at longer λ But portable High limit of detection (not suitable for potable water) Really only suitable for standard solutions (of high concentration)

Iodometric titration

Same sequential titration principle as amperometric titration Suffers from interferences when multiple oxidants are present Requires skilled technician Really only suitable for standard solutions (and how Palintest standardise solutions)

 9. Laboratory methods are not conducive to complying with DWI guidelines

 10. Is it possible to comply with the DWI guidelines?

Careful monitoring and dosing control at generator Downstream monitoring must incorporate On line monitors Sampling for laboratory (IC) assessment Portable monitoring

10 Things you now know about TRO:
1. Total residual oxidants include ClO2, ClO2- and ClO3- (and chlorine)
2. DWI regulations are relatively stringent
3. On site analysis is the only way of complying with DWI regulations
4. DPD is no longer a standard method
5. Other colorimetric methods are available
6. Colorimetric suffers from difficulties in the field
7. Photometric dye bleaching susceptible to operator error
8. ChlordioX™ Plus enables compliance with most of DWI requirements
9. Laboratory methods alone are not conducive to complying with DWI guidelines
10. It is difficult to comply with the current DWI guidelines