Volume Reduction Technologies and Practices
Many industries apply one or more volume reduction technologies for the main purpose of wastewater minimisation. Most commonly used volume reduction technologies include:
- Desalination processes.
- High recovery processing and hybrid water treatment systems.
- Brine concentrators.
- Crystallisers.
- Evaporation ponds and enhanced evaporation systems.
The application of the above volume reduction processes, individually or in various combinations, commonly requires the use of any number of supplementary processes such as nanofiltration, ultrafiltration, microfiltration, ion exchange, chemical coagulation, carbon capture and other pretreatment steps. In most cases, over 90% of the operating cost of thermal volume reduction processes is the energy cost. Developed in the U.S. primarily for application to energy generation industry, Zero Liquid Discharge (ZLD) concept represents the extreme case of volume reduction, whereby no liquid waste is allowed to be discharged from the operational area. While expensive and highly energy intensive, ZLD processes are required by law in certain industries (i.e., power generation and food industries in the U.S.). It is only recently that the concept of ZLD has progressed closer to a reality in other industries and countries, because of increasing limitations with availability of discharge options particularly for large flow waste streams. The most recent example is the Australian coal seam gas industry, with most CSG-LNG developers currently considering a variety of volume reduction technologies for reducing the need for evaporation ponds.
Issues
The key to effective volume reduction is the efficiency of salt load and contaminant load reduction, as a brine stream progresses through successive volume reduction steps.
In the case of solar evaporation, despite the effectiveness of solar ponds for reducing brine volume at low salinity levels, at higher salinity levels the evaporation rate of such ponds is dramatically reduced. Further, evaporation ponds should be complimented with properly designed and constructed crystalliser ponds, to enable the production of solid salt mixture for subsequent landfill disposal. Otherwise, an evaporation pond which is continuously topped up with fresh brine will not produce a solid stream, unless it is converted to a crystalliser pond or salt is selectively extracted from the pond water by chemical reaction means.
In the case of thermal evaporation, the performance of thermal equipment (brine concentrator and crystalliser) will largely depend on feed water salinity level and its chemical composition. For this reason, pre-treatment may be required to ensure a satisfactory evaporation rate and to reduce the footprint of the thermal equipment.
Solutions
The solution offered by Geo-Processors’ is based on the proven SAL-PROC™ technology. This technology enables effective volume reduction by adjusting the salt load and chemistry of the feed to reduction units, whether solar or thermal. This process also produces solids in the form of commercial grade salts and mineral by-products that may be sold or recycled, in order to offset the treatment costs and reduce the need for landfill disposal. Thus, the advantages of Geo-Processors’ brine solutions are several fold:
- Improving the efficiency of thermal evaporators and crystallisers, by means of:
- Reduction of salinity.
- Reduction of concentration of metallic / organic inhibitors and by.
- Controlling the salting point of salts through either selective precipitation processes or mineral phase change.
- Causing improved water recovery in secondary desalination or thermal volume reduction processes for reducing the size of equipment and the overall footprint of the treatment system.
- Reducing land requirement.
