Your paper and cardboard production business may treat water or liquid effluents on site, for example using an effluent treatment plant.
Water pollution incidents involving dyes and suspended solids are the most common complaint downstream of paper mills. Make sure that you treat and remove colour from any wash waters before you discharge them to the environment.
Check if you need authorisation to discharge wastewater
Before you discharge wastewater to surface waters or groundwater, you must have authorisation from the Northern Ireland Environment Agency. Your wastewater may be contaminated with a wide range of organic water-soluble pulp components. You will need to treat effluent extensively before you can discharge it to surface waters or groundwater.
Before you discharge wastewater to a sewer, you must get permission from NI Water. You may need to pre-treat your effluent before you discharge it to the sewer.
You must comply with all of the conditions in your authorisation or you may be prosecuted and fined or sent to prison.
If you have an effluent treatment plant you must manage it carefully to comply with the conditions of your authorisation. For example, you may need to monitor and stay within specified limits for the main components of your discharges, such as flow rate, pH, temperature, suspended solids, or chemical oxygen demand. These requirements and limits will be explained in your authorisation.
Comply with waste sludge and screening responsibilities
Materials discarded from your effluent treatment plant, such as sludges and screenings, are classed as waste. You must comply with your duty of care responsibilities when dealing with these and other waste - see waste responsibilities for paper and cardboard producers.
You may need to deal with some sludges and screenings as hazardous waste - see hazardous waste responsibilities for paper and cardboard producers.
Review your chemical use
If you use biocides for system cleaning, slime control and in de-foamers, consider using biodegradable biocides that degrade quickly, such as guanidine and isothiazolones.
Avoid using chlorine-containing bleaches or chlorine-bleached pulps. Bleaching chemicals react with organics and place a considerable load on water treatment systems.
Don't overdose water with water treatment chemicals, especially those containing halogens, eg chlorine and bromine. Use chlorine dioxide in place of halogenated disinfectants for high organic loads.
Use dyes with solid pigments where they can be treated by clarification.
See the page on raw material use in paper and cardboard production.
Manage your effluent treatment plant correctly
Make sure that your systems are designed so that effluent cannot bypass the treatment plant.
If you make a change to your process, always consider the effect this will have on your treatment plant. Effluent treatment plants are designed for specific processes, depending on the quality and quantity of the effluent. For example, if you implement water minimisation measures the concentration of your effluent will increase.
If you carry out batch processes, you should manage your effluent carefully to avoid discharging large quantities to the treatment plant at one time. These 'shock loads' could affect the treatment plant's performance.
If there are a lot of coloured fines during de-inking, consider using dissolved air flotation (DAF) or membrane technology. You can use DAF as a primary effluent treatment, as well as in the de-inking process.
Balancing tanks can help to mix and standardise your effluent. Sludges with poor settlement characteristics (bulking) can be treated by stabilising fluctuations in effluent pH, flow, load and tank conditions and by maintaining your plant regularly.
Treat effluents containing suspended solids separately. This will prevent problems in biological treatment plants.
Cover containers to prevent emissions and odour from chemicals and sludge.
Monitor and maintain your treatment plant
Monitor your effluent plant regularly to make sure it is operating effectively. You could use turbidity meters to monitor effluent quality continuously.
Check your sewerage and effluent disposal costs. Establish a baseline and investigate when costs deviate from it. This could save you money.
Employ suitably qualified engineers to make sure the treatment plant is designed to produce the required quality of effluent and that it will operate effectively.
Minimise the amount of sludge you produce
Reduce the volume of sludge you produce by using dewatering presses or centrifuges. For example, use centrifuges to separate fines in white water and recover reusable material in your production process.
Reduce the load on your treatment plant by minimising your waste and monitoring the volume of water used by your business.
Recycle wastewater whenever possible to reduce the input and load on your water treatment systems. Reducing the water content of the sludge can reduce your waste management costs.
Use water efficiently
Save money on your effluent treatment costs and your water supply by using water more efficiently. You should recycle and reuse water within your process wherever possible.
Keep your wastewater streams separate. This will make it easier to reuse the water and also prevent large wastewater streams being contaminated with concentrated toxic streams.
See the page on water use responsibilities for paper and cardboard producers.