Kristal® in Textile Wastewater Recovery

Introduction

A textile factory in Bogota, the capital city of Colombia, relies on Kristal® to reclaim most of its 2000 m3 of daily produced wastewater. Functioning as a UF pretreatment before RO, Kristal® keeps the lifespan of the RO membranes to a maximum, while at the same time improving the flux and providing a high UF recovery rate of about 93%.

Despite improvements in water supply and sanitation in Colombia over the past few years, quality of water supply and sanitation remains relatively inadequate. In 2008, only 72% of the population that received public services had access to water of potable quality. Furthermore, not enough was being done to control the quality of wastewater discharge. For example, only 25% of the wastewater generated in the country underwent any kind of treatment in 2006, as published by Superintendency of Sanitary Services (SISS).

With the combined  UF + RO wastewater plant, the Colombian textile company is not only able to reclaim 85% of its wastewater to be reused as process water, thus significantly cutting down its water consumption, it also greatly contributes to reducing wastewater discharge. This helps the factory to save water and energy costs, as well as wastewater discharge fees imposed by the government.

 

System

30 Kristal® modules are installed, producing close to 2 MLD of UF permeate water to be fed into the RO system. The modules are arranged into three trains, having 10 modules on each one. Operating at about 93% recovery rate, Kristal® enables the treatment plant to reclaim a total of 1.7 MLD of RO product water. That’s a high 85% overall recovery!

The UF system cleaning is automated, performing backwash on one skid every 30 minutes of operation, while the remaining two trains stay in operation. Chemical cleaning is conducted on a weekly basis as a preventive measure to membrane fouling.

 

Process

Textile wastewater coming from the factory first passes through a mesh filter to remove its lint. The water is then directed into a lavatory tank for gas washing, lowering its pH to 6-7. A heat exchanger cools the water to 35°C and transfers the heat to other process streams. The water is then sent to a homogenization tank for 2-hours of mixing, and during this time, heavy solids settle to the bottom of the tank and are pumped to sludge beds.

The remaining water enters an ozone contact tank for oxidation to remove 30% of its colour. Remaining solids in the water are removed by electro-coagulation/flocculation, and a sedimentation tank allows sufficient time for the solids to settle. Water passes through a 50 micron filter before entering Kristal® UF system, where turbidity is reduced by >95%. The UF permeate then enters a two-pass RO system, and the final product water is taken to the factory process tank for reuse.

 

Conclusion

The UF + RO plant has not only ensured a continuous supply of water to the textile factory, it also provides process water that is of consistently good quality.

Water Quality UF Feed UF Permeate
Turbidity (NTU) 20 > 1
Iron (ppm) 3.25 0.04
Colour (PTCO) 340 60