One of the main issues for the chemical and pharmaceutical industries is the production of hazardous effluent (liquid waste).
Techniques for treating hazardous effluent
Techniques your business could employ to treat the effluent it produces include:
- Diversion - it is important that your business has diversion systems in place. These redirect any hazardous effluent from your processes into a temporary storage facility. You can then deal with the discharge appropriately at a later date.
- Equalisation and balancing - if you can control fluctuations in the characteristics of the effluent, your waste can be dealt with more easily by subsequent treatment processes.
- Neutralisation - some of the effluent your business produces may be acidic or alkaline. It is important to neutralise the pH of these streams as soon as possible to help with disposal. If your site has both acidic and alkaline effluent, consider combining these at your diversion facility. This minimises your effluent disposal costs.
- Dissolved air flotation - this method of effluent treatment is usually used to remove any suspended solids and part of the effluent's organic load prior to any further treatment downstream.
- Wet air oxidation - the pre-treatment of some high chemical-oxygen-demand effluents can be achieved by oxidation of the organic pollutants at high temperature and pressure using air, hydrogen peroxide or oxygen. You can use wet air oxidation to convert organic compounds to CO2, water and nitrogen or break down more complex structures within the effluent before further treatment.
- Activated sludge - this effluent process is an aerobic biological treatment in which bacteria and other microorganisms feed on biodegradable organic material in the effluent and degrade it. However, the microorganisms do require nutrients such as nitrogen to support their growth.
- Sludge thickening and dewatering - these are mechanical processes that are designed to reduce the volume of sludge. Methods currently in use include gravity thickeners, decanters and drum thickeners. This technique is usually carried out using a centrifuge, belt press or plate-and-frame press.
Check if you need authorisation to discharge wastewater
Your effluent may contain increased levels of contaminants such as heavy metals, hydrocarbons, resins or solvents.
Before you discharge wastewater to surface waters or groundwater, you must have authorisation from the Northern Ireland Environment Agency (NIEA). 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.