Don't fall foul of waste water regulations
Avoid the disaster of being fined for pollution by your local water authority by keeping your effluent within agreed limits.
There’s no getting round it: if you are a printer, you are likely to be a polluter. No single process or technology is free from environmental impact but failing to control your effluent can hit hard in the short-term with fines and even blocking off your drains.
Keep it clean
First off, subject to local legislation you must register as a waste producer to regularly dispose of waste; penalties are stiff if you do not – for example, up to £5,000 in the UK. Printers, like all businesses that produce hazardous waste, have a duty of care to their workers, the general public and the environment. This starts with the paperwork – you must classify your waste and supply the paperwork to the licensed waste management contractors that you use, and any environmental inspection officers who may want to check that you are sticking to the rules.
You cannot try to get around your consent limit by diluting with domestic waste water from your kitchen and bathroom
If you are trading, whatever the size of your premises, the effluent you produce is classified as trade effluent and you are likely to require a permit from your local water company or an exemption certificate. Screen printing and digital printing use different chemicals and have different waste profiles, so do not be surprised if your limits and charges don’t tally with neighbouring companies. Water-based inks might sound like they can be tipped safely down the drain, but they can not. As part of a holistic, sustainable waste policy, you should identify where you may be able to retain ink for future use. It’s in your interest to have cleaner water because you will pay less to have it disposed of.
Limits for water-borne effluent vary greatly between countries, between water companies, and between neighbouring businesses. The closer you are to a processing plant, the more stringent the limits set will be as there will be less opportunity for others’ waste water to dilute your own. The only way to find out what your limits are is to ask your local water authority. The water authority sets the consent limit – the amount of effluent you can push through into the sewerage system – and enforces it. Talking to your local water company and getting your limits right means you can avoid non-compliance, and the improvement notices and/or fines that could be heading your way. Water companies even have the power to shut you off – to plug your drain and stop you putting anything into their waste water system at all.
Compliance will save you money and understanding processes will increase likelihood of compliance
Consent limits set by the water company stipulate how much water you can simply flush down the drain. Anything above this will have to be professionally disposed of by a contracted waste management company or subject to filtration or treat prior to discharge. Limits will include maximum volume, suspended solids, oil content and temperature, pH and COD (chemical oxygen demand) and BOD (biological oxygen demand).
COD indicates the total amount of all chemicals in the water that can be chemically oxidised. BOD, which takes longer to test, indicates the amount of organic matter that can be biologically oxidized. Higher BOD/COD levels mean a greater amount of oxidisable organic material, which reduces dissolved oxygen levels. Less oxygen can lead to anaerobic conditions, which is harmful to higher aquatic life forms.
Spirit of compliance
There are also certain hazardous chemicals that should not be poured down the drain, for example white spirit, which kills the natural bacteria used by processing plants to break down waste.
You cannot try to get around your consent limit by diluting with domestic waste water from your kitchen and bathroom – any samples of your water taken by environmental health inspectors will filter domestic effluent out to take a reading.
As we have seen, consent limits for drain disposal vary widely, but typical limits may be along the lines of COD not exceeding 2,000mg/litre, a pH of 5 to 10, water temperature of under 43 degrees Celsius, and no more than 1,000mg of suspended solids. Printers are likely to exceed these limits in COD and suspended solids. Textile printers using non-digital rotary printers, steam fixation and washers are likely to exceed volume limits.
Manufacturers and product suppliers should be able to furnish you with details of the ecological and biodegradable make-up of inks and screen washes.
Focus on screen printing
William Shorter, Technical Executive and Product Line Manager – Remco at SPT Sales and Marketing, is a specialist in waste water. He explains how screen printing processes affect your waste water. Water-based inks contain solvents and contribute to COD, solids and affect pH.
“A single screen with 1m2 of emulsion on a 120cm mesh would have a COD of up to 150,000mg/litre,” he says. “This would require 75 litres of water during washout to get COD below 2,000mg/litre. Cleaning, ink and screen wash will both have COD of approximately 1,500,000mg/litre.”
Bigger firms can consider water balancing systems, filtration and chemical treatment. But smaller firms can take cheap and easy steps too. William recommends giving your processes an overhaul. You can scrape emulsions back from the coating trough back to the pot, fit mesh filters to the waste water system, and try to use water dilutable cleaning solvents such as an aquawash and apply less caustic haze removers. “Hold back waste water and pH neutralise it,” he adds. “Compliance will save you money and understanding processes will increase likelihood of compliance.”
Cleaning up your effluent – next steps
- Identify sources of trade effluent and try to keep them separate so you can monitor each one. For example, note the colours of emulsions so the blue/green water can be sampled separately, and action taken if that individual source is non-compliant.
- Monitor your processes.
- Keep an eye on your measured water colour, pH, temperature.
- Work with chemical supply company on COD, BOD, solids.
- Cooperate with your local water authority and ask them for advice.
- Bigger firms: invest in effluent balancing systems.
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