Study On The Advanced Treatment Of Wastewater From Cooling Tower With Integrated Membrane System

Seventy to eighty percent of industrial water is cooling water and cooling systems let off much wastewater everyday. It is worthful to treat and reuse the wastewater from cooling towers (WCT). In this paper, the quality of WCT was analyzed. Based on the results of water quality analysis, the MF (UF)-RO integrated membrane systems (IMS) was adopted to treat WCT. The pilot scale device was designed and established. Microfiltration (MF) and ultrafiltration (UF) are used to remove the suspended particles, microorganisms and colloids in the WCT. The membrane performances of MF and UF were investigated and appropriate operation modes were explored. The experimental results show that this mode (production: 40～50minutes; backwash 50～90 seconds; flush 1 minute.) could maintain the membrane performance of rejection and permeability. The product turbidity of MOF910, TH-4040 and HF-35-82-PMC membrane is below 0.5 NTU and silt density index (SDI) is less than 3, which could meet the requirements of reverse osmosis (RO) feed. The normal water fluxes of three membranes are: MOF910 MF membrane, 100L/ (m2.h) at pressure of 0.06 MPa; TH-4040 UF membrane, about 80L/ (m2.h) at pressure of 0.14 MPa; HF-35-82-PMC UF membrane, about 70L/ (m2.h) at pressure of 0.11 MPa. It is the algae and adsorbed particles that cause the sustaining decline of membrane flux. Sodium bisulfate solution and sodium hydroxide solution could be used as cleaning reagents to remove those fouling effectively. The products of MF and UF were treated by LFC1-4040 and TFC-HR-4" RO membrane modules. The results show that RO total salt rejection is over 99%. Especially, the rejection of bivalent ions such as Ca²⁺, Mg²⁺ is 99.5%. The quality of RO product could meet the reuse requirements. The water fluxes of two RO membranes are: LFC1-4040 membrane, 25 L/ (m².h) at pressure of 1.0 MPa; TFC-HR-4" membrane, 26～28 L/ (m2.h) at pressure of 0.8 MPa. On the basis of the above experiments, a plant with 1200 T/d product water was designed, and an economic analysis was carried out on the plant. It shows that the plant has good economic benefit and remarkable social benefit.