Zero Liquid Discharge (ZLD)
A ZLD treatment system utilizes advanced technological water treatment processes to limit liquid waste at the end of your industrial process to, as the name suggests, zero.
An efficient and well-designed ZLD treatment system should be able to:
- handle variations in waste contamination and flow
- allow for required chemical volumes adjustments
- recover around 95% of your liquid waste for reuse
- treat and retrieve valuable byproducts from your waste (i.e. salts and brines)
- produce a dry, solid cake for disposal
A ZLD treatment system will also help your facility meet stringent effluent requirements, such as the U.S. Environmental Protection Agency’s Steam Electric Power Generating Effluent Guidelines. Just keep in mind your facility’s requirements will vary based on whether you are discharging into a publicly owned treatment works (POTW) or to the environment under a National Pollutant Discharge Elimination System (NPDES permit).
What’s included in a basic ZLD treatment system?
The exact components of a ZLD treatment system will largely depend on
- the volume of dissolved material present in the waste,
- the system’s required flow rate, and
- what specific contaminants are present. But in general, a basic ZLD treatment system typically includes some type of:
- clarifier and/or reactor to precipitate out metals, hardness, and silica
- chemical feed to help facilitate the precipitation, flocculation, or coagulation of any metals and suspended solids
- filter press to concentrate secondary solid waste after pretreatment or alongside an evaporator
- ultrafiltration (UF) to remove all the leftover trace amounts of suspended solids and prevent fouling, scaling, and/or corrosion down the line of treatment
- reverse osmosis (RO) to remove the bulk of dissolved solids from the water stream in the primary phases of concentration
- brine concentrators to further concentrate the reject RO stream or reject from electrodialysis to further reduce waste volume
- evaporator for vaporizing access water in the final phases of waste concentration before crystallizer.
- crystallizer to boil off any remaining liquid, leaving you with a dry, solid cake for disposal/li>
Depending on the needs of your plant and process, these standard components are usually adequate, however, if your plant requires a system that provides a bit more customization, there might be some features or technologies you will need to add on. Because of the broad range of industries that use ZLD and the various waste streams produced, ZLD is a highly custom process and these add ons will depend on your facility’s individual needs.
Mechanical vapor recompression (MVR) is an energy recovery process which can be used to recycle waste heat to improve efficiency. Typically, the compressed vapor is fed back to help heat the mother liquor in order to produce more vapor or steam.
The mechanical evaporator process offers an alternative to steam from a boiler as the heat delivery source, utilizing a mechanical device such as a compressor or turbofan to generate the heating vapors (steam) required on the heating side of the heat transfer surface.
Mechanical Vapor Recompression (MVR) is a proven energy-saving evaporative concentration technology, which reduces evaporation energy use by 90% or more. … The energy normally lost in the compression is recovered, leading to a highly-efficient evaporation process.
The vacuum evaporation treatment process consists of reducing the interior pressure of the evaporation chamber below atmospheric pressure. This reduces the boiling point of the liquid to be evaporated, thereby reducing or eliminating the need for heat in both the boiling and condensation processes.
Forward osmosis (FO) is a water separation process in which a semipermeable membrane is used to separate water from dissolved solutes. FO uses natural energy in the form of osmotic pressure to transport water through the membrane while retaining the dissolved solutes on the other side.
Typical areas of application for Forward Osmosis (FO) process are sea water desalination, zero liquid discharge, water recycle and reuse, dewatering of high value product stream etc.
Hydromo Technologies’ hybrid FO combines of Forward Osmosis process with Nanofiltration, Reverse Osmosis (RO) or MD system for draw solution recovery. Draw solution selection and subsequently recovery method of draw solution depends on application, feed water quality and product requirement. Our few pilot and commercial tests showed successful outcomes to our clients in achieving more than 75% of water recovery and 50% reduction in energy consumption.
Advantages of Forward Osmosis (FO):
- High water recovery
- Low operational pressure
- Simple, easy and integrated design
- Minimized waste
- Low energy consumption per unit of water recovered
- Low capital investment
- Low operation and maintenance costs
- Less fouling and scaling
- Longer membrane life
- Ability to treat complex wastewater
- Modular structure
- Industrial Wastewater Recycle
- Zero Liquid Discharge
- Sea Water Desalination
- Produced Water Reuse
- RO Reject Minimization
- Brine Concentration
- Concentrating Juices and Beverages
- Concentration of Skim Milk and Dairy Products