Drain Safe Products: They’re Waste Water Compliant, Right? Wrong!

Drain Safe Products: They’re Waste Water Compliant, Right? Wrong!William ShorterCPS Technical Sales Executive/Product Manager

Introduction – William Shorter

• Technical Sales Executive UK / Product Manager.

• CPS – Chemicals Products & Services– Established in 1982 in Denmark.– Located in Oxfordshire, UK.– Division of MacDermid Autotype Ltd.

• Involved in screen printing for over 21 years.• Carried out waste water audits for large to small

screen printing companies.

Drain Safe Products: They’re Waste Water Compliant, Right? Wrong!

Clean water and good sanitation is taken for granted by millions of people in the ‘developed’ world. We simply turn on a tap for clean drinking water and allow it to wash into a sewer for treatment in some unseen facility. We also expect to walk alongside unpolluted rivers and waterways that are full of fish and wildlife.

Drain Safe Products: They’re Waste Water Compliant, Right? Wrong!

• The purpose of this presentation is to offer a practical guide on some of the issues related to screen making chemicals and how they can impact waste water.

What does ‘Drain Safe’ mean to you as a screen printer?

What does ‘Drain Safe’ mean to you as a screen printer?

Potential Answers:1. It’s safe to go down the drain.2. Compliant with waste water regulations.3. Does not contain banned chemicals.4. All of the above.5. None of the above.

Link to Screen Printers Of The World Unite Community post: https://plus.google.com/+WilliamShorter/posts/iQmYkdqaXnL

Waste Water Regulations

• Waste water regulations are probably the most diverse set of ‘environmental’ standards.

• The closer you are to the waste water treatment plant the stricter these limits can be.

• It is likely that your business has different ‘consent limits’ for waste water compared to your neighbours, depending on the nature of their work.

What is trade effluent?

• Trade effluent is any liquid waste (effluent), other than surface water and domestic sewage, that is discharged from premises being used for a business, trade or industry. Trade effluent can come from both large and small premises.

Waste Water Regulations

• Water authorities such as Thames Water, Seven Trent etc. stipulate and control the consent limits of trade effluent.

• It is ‘your’ responsibility to inform your water authority that you are discharging trade effluent to the drain.

Can you afford to be non-compliant?

• Non-compliance is a very serious issue and penalties can range from improvement notices, fines, or prevention from discharge into the drains which would necessitate all water being collected for disposal as ‘chemical waste’ at a huge cost and inconvenience to the business.

Making Sense of the Terminology

• Consent limits stipulate what and how much ‘trade effluent’ you are allowed to discharge into the drains.

• Consent limits stipulate.– Maximum volume– Maximum solids limit– Temperature range– COD– pH range– Types of chemicals permitted

• Petroleum spirits (white spirit) and some aromatic hydrocarbons (general purpose screen wash) are unlikely to be permitted to enter a public sewer.

Making Sense of the Terminology

• COD (Chemical Oxygen Demand) is the most misunderstood parameter and the one that causes most problems with effluent from the screen making process.

• COD is a measure of how much oxygen is required to break down the ‘waste’ materials in the water at the treatment plant.

• Many sewage treatment facilities use a cocktail of bio-organisms to ‘feed’ on the waste, but if the COD in the water is too high they will run out of oxygen and die.

Understanding Consent Limits

• Consent limits apply to specific sources of trade effluent.

• Domestic effluent (toilets, kitchen etc) does not contribute and is not considered in the consent limit.

Understanding Consent Limits

Typical example of consent limits values could be:-– COD: <2,000 mg/Litre– pH: 5 to 10.– Water temperature: <43°C.– Solids: <1,000mg/Litre (i.e. 1 gram/Litre)

• Most screen printers will exceed these limits.

What does ‘Drain Safe’ mean to you as a screen printer?

What does ‘Drain Safe’ mean to you as a screen printer?

How did people vote? (in a survey carried out 11/09/15)

1. It’s safe to go down the drain.

2. Compliant with waste water regulations.

3. Does not contain banned chemicals.

4. All of the above.5. None of the above.

21%

13%

13%

53%

Percentage

Drain Safe is Okay, Right? – Wrong!

‘Drain Safe’, actually means the product does not knowingly contain any chemicals that are banned from entering the waste water system, it does not guarantee compliance and therefore should not be assumed is okay. - remember the points we talked about earlier - • Your type of business• Your proximity to your local water authority• Each water authority can have different compliance

regulationsFor example, releasing too much hot water into the drains would be non-compliant, even though the water itself is 100% ‘drain safe’!

Screen Making Processes affect waste water

Screen Making Processes affect waste water

• Unexposed emulsion washed out after exposure.

– A single screen with 1m2 coating of emulsion on a 120/cm mesh would have a COD of up to 150,000mg/Litre and would require around 75 Litres of water during washout to get the COD below 2,000mg/Litre.

– Contributes to the pH (acidic), solids content and colour of the waste water.

– Direct to screen inks will also contribute to the solids, pH and COD of the waste water.

Screen Making – contributes to waste water

• Ink Cleaning

– The waste water from this process may be neutral, acidic or alkali.

– The ink and screen wash both individually have a COD of approximately 1,500,000 mg/Litre.

– The ink will contribute to the solids content and colour of the waste water.

Screen Making Processes affect waste water

Is water based ink safe or not safe to go down the drain?

Screen Making Processes affect waste water

• ‘NO’, because

– Contains solvents!– Contributes to the COD and

solids.– May also affect the pH.

Screen Making Processes affect waste water

• Stencil Removal

– Stencil removers on average have a pH of 2.

– The inorganic raw materials in the stencil removers will not contribute to the COD.

– Dissolved cross linked emulsion contributes to the COD, solids and water colour.

Screen Making Processes affect waste water

• Haze Removal

– The waste water from this process will always be alkali.

– The haze remover and ink stain will contribute to the solids, COD and colour of the waste water.

Identify your sources of trade effluent

Identify your sources of trade effluent

• Monitor your process– Screen Cleaning– Making

• Take note of or measure the:– Water Colour– pH– Temperature

• Work with your chemical supplier / screen printing supply company.– COD ,BOD, Solids etc

• Work with your water authority.

Controlling conformance to consent limits

Controlling conformance to consent limits

• Emulsion & Stencil Removal:– Simple steps:

• Scrape emulsion from your coating trough back into the pot.• Fit filters to the waste water system.• Hold waste water back and pH neutralise.

– Haze Removal waste water.

– Complex & expensive steps:• Centrifugal filtration.

– Emulsion solids.• Chemical waste water treatment.• Dip tank, cleaning machine or recirculation unit.

– Sludge disposed via waste handling company.• Balancing tanks.

Controlling conformance to consent limits

• Screen Wash & Ink:– Simple steps:

• Scrape as much ink as possible from your screen prior to cleaning with screen wash.

• Fit fliters to the waste water system*.• Use a water dilutable cleaning solvent such as an Aquawash.• An Aquawash diluted at 1:1 with water will have a typical

COD value of 750,000mg/Litre, diluting at 2:1 with water will reduce this to 500,000mg/Litre.

• Hold waste water back and neutralise.

*Note water based inks and screen wash will not be removed by filtration as they are water soluble.

Controlling conformance to consent limits

• Screen Wash & Ink:– Complex & expensive steps:

• Centrifugal filtration.– Ink sludge

• Chemical waste water treatment.• Dip tank, cleaning machine or recirculation unit.

– Dip tank & cleaning machine sludge disposed via waste handling company.

• Balancing tanks.

*Note water based inks and screen wash will not be removed by these treatment processes above as they are water soluble.

Controlling conformance to consent limits.

• Haze Removal:– Simple steps

• Using lower caustic haze removers,• Apply the minimum amount of haze remover and if possible

use a coating trough to apply the haze remover to the mesh.• Hold waste water back and pH neutralise.

– Stencil Removal waste water.– Complex & expensive steps:

• Centrifugal filtration.• Chemical waste water treatment.• Balancing tanks.

Summary

• Understanding your processes can increase the likelihood of compliance.

• Compliance is not easy but simple steps can be taken to increase likelihood of conformance.

• It is your responsibility to inform the water authority of what you are discharging down the drain.

• Compliance will save you money in the long term.

• Drain Safe Products: They’re Waste Water Compliant, Right? “Wrong!”

CPS LtdChemicals Products and Serviceswww.cps.eucps@cps.euT: 01235 773240F: 01235 771196

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