Effluent Treatment
The objective of any effluent treatment program is to maximise the removal of contaminants before discharge to trade waste or treat water to a quality where it can be reused.
This treatment program typically requires 3 processes:
1. Chemical Treatment (Flocculation/Sludge Removal)
Process involves adding polymers (inorganic or organic) to the incoming raw effluent after some pH adjustment if necessary to attract the suspended solids in suspension to form small pin flocs. Addition of the polymers is more effective if added in a region of adequate mixing to promote collisions between suspended solids and polymer molecules.
An effective polymer treatment program will generate between 4-6 times additional sludge volume which can impact on costs to remove this sludge off site. There are now effective technologies now employed by various industries to dewater this sludge which include belt presses, natural cone tanks and geotubes.
Geotextile bag, typically supported on a steel frame where water seeps out under pressure from a pump. Generally, low capital cost but very effective.
2. Biological Treatment
This system involves employing either anaerobic or aerobic processes to remove considerable amounts of dissolved and colloidal organics.
Typical traditional options for biological treatment for BOD removal are:
- Activated Sludge
- Trickling Filters
- Oxidation Ditch
- Ponds / Wetlands / Lagoons
In the last 3-10 years, there has been development of smaller, low cost and more effective methods such as the Fixed Media Bio-Filtration (FMBF) process which can achieve BOD levels < 10 mg/L with no limit to the % of effluent available for recycling. The advantages offered by the FMBF process are:
- No free biomass (no sludge removal or biomass polishing)
- Lowest odour risk of any biological process
- More tolerant to changing conditions
- Physical media cannot die and has a high re-growth rate of 1-2 weeks.
- Residence time not time limited - more media can be added as required
- High performance option
3. Tertiary Treatment
This process would typically follow a biological process which produces high quality water suitable for re-use in the plant. Depending on the type of effluent and contaminant levels, recovery rates are typically 60-70%
Before a process can be employed, secondary treatment (i.e. biological) must reduce BOD levels to below 50 mg/L to prevent gross fouling of the membranes.
The quality of the water is generally suitable for re-use as make-up to cooling towers or boilers. This is currently at a number of industrial plants in Australia.
Our Technical Specialists will work with your team to select and implement the most effective program centred on meeting your environmental goals, reducing your operating costs, and keeping you on the "cutting edge" of technology. We will work with you to develop joint process improvements that will optimise operating efficiency and save on operating costs.