We propose to develop a field-deployable system for testing the possibility that employing membrane separations in rendering plant wastewater treatment processes. Wastewater from rendering industry is a kind of high strength industrial wastewater which contains significant amount of suspended solids, fats oils, greases and proteins. Dissolved air flotation (DAF) is the most popular method for primary treatment, but DAF has limitations that polymer coagulants and other chemicals must be added to enhance flocculation efficiency and maintain pH. In this project, we suggest using ceramic membrane as a primary treatment method for oil/water separation to replace DAF. The project was supported by Anima Co-Products Research and Education Center (ACREC) from Clemson University. Dr. Ladner, Dr. Zheng, Weiming, Joe and Matt contribute to this project.
We have created a pallet membrane system (figure 1) that consists of software interface and fluid-handling hardware. The hardware portion has different components which are operated by software to realize filtration, backwash and chemically clean automatically.
The components of this system are as follows:
- Ceramic membranes are fabricated by Inopor with mean pore sizes of 100 and 200 nm. The effective membrane area is 0.025 m2.
- Three pumps are used for creating feed flow, backwash flow, and chemical cleaning flow, respectively.
- Four solenoid valves are employed to control the flow entering or leaving the module during filtration, backwash, and chemical cleaning.
- An actuator valve is used at the concentrate port to control pressure and flux.
- Two pressure gauges and transducers are used to measure the pressure at the concentrate port and backwash port.
- A flowmeter is installed at the permeate port to measure the pressure, temperature, and flowrate of the permeate.
- Three sensors are inserted into the feed tank, and pH, temperature, and conductivity are measured and recorded.
- A balance is mounted before the permeate tank. According to the balance reading, the flow rate is calculated which works as a reference to the permeate flow meter.
The program (figure 2 and 3) in LabVIEW involves three main components: filtration loop control, actuator auto-adjustment, and data acquisition and analysis. The filtration loop control program is the fundamental part, which adjusts pumps, solenoid valves, and the actuator valve to achieve automatic backwash and chemical cleaning. Filtration, backwash and chemical cleaning periods can be set respectively at the beginning of the program manually. During filtration, the membrane is fouled and flux declines. An actuator auto adjustment program was coded to maintain either constant pressure or constant flux. For example, in constant-flux mode the program automatically closes the valve a little to provide a higher trans-membrane pressure and maintain the same flux. The program can record and analysis data in running time.
We record the characteristics of wastewater in feed tank (Temperature, Conductivity and pH), operating status of membrane module (concentrate pressure, permeate pressure, permeate flux and permeate flow rate) and the setting of the system (filtration time, backwash time, chemical cleaning time, pump speed, target pressure/flux, and so on). All of the data will be plotted and analyzed via a program built in MATLAB, there is an example plot in figure 4.
Based on the system we built, we will further our research on different cleaning strategies to the ceramic membrane fouled by the fat, oil and grease (FOG) wastewater.