SUEZ technology enables world’s first zero liquid discharge (ZLD) at a corn mill
|Technology||:||Ultrafiltration (UF), activated carbon filters (ACF), reverse osmosis (RO), membrane bioreactor (MBR), salt crystallizer|
A corn mill in southern India was facing strict government regulations regarding effluent discharge. First, the government requires a water treatment solution that provides the mill with consistent product quality for drinking water and boiler feedwater purposes. Second, the mill needs to maximize wastewater recycling due to limited land for irrigation. Third, the government required the facility to have zero liquid discharge (ZLD).
SUEZ proposed a solution involving a freshwater treatment system, sanitary waste treatment system, recycle wastewater treatment system, and ZLD schemes.
The freshwater system features immersed UF with ZeeWeed* 500D membranes, followed by ACF to remove organic contaminants and pesticides. Filtered water from the ACF is then passed through RO membranes to remove trace residual organics, pesticides, and coliform in the water. UF reject and backwash waste from the ACF system is recycled to the backwash water recovery system.
The ZeeWeed 500D membranes can accommodate a variety of total suspended solids (TSS) values without the use of chemicals. RO reject from the freshwater system is transferred to the recycle water treatment plant’s RO system for further treatment.
The recycle wastewater system uses SUEZ’s advanced, low energy LEAPmbr* technology, which oxidizes the organics in the wastewater, and separates the mixed liquor suspended solids (MLSS) to provide a treated water quality with a very low inorganic and suspended solids content. LEAPmbr improves productivity by 15% and lowers total power consumption.
LEAPmbr is followed by ACF, then a two-stage RO system. This combination produces water that is fit for boiler feed and cooling tower make up.
For the ZLD system, RO reject (brine) is transferred to the evaporation system, where crystallization concentrates the solution above the saturation point to enable uniform nucleation and growth of salt crystals. Crystals are discharged from the centrifuge with dryness around 85% w/w and condensate is recovered to be reused in the process.
In the sanitary treatment system, raw sewage from the factories are collected, and treated using SUEZ’s Z-MOD* MBR system. Z-MOD removes pollutants such as COD, BOD, and TSS before discharge to irrigation as per discharge norm.
The company commissioned SUEZ’s treatment solutions and in doing so, has ensured consistent treated water quality. With implementation of this scheme, reuse has been maximized to limit irrigation water discharge to 48 m³/d and has ensured 25% excess capacity in ZLD.
*Trademark of SUEZ; may be registered in one or more countries.