Group 4 | 5ChEC

February 1, 2014

Casillan|Feleo|Liggayu|Manabat|Taruc|Trumata

Article Report

S. R. H. Abadi, M. R. Sebzari, M. Hemati, F. Rekabdar, T. Mohammadi

Background of the Study

Oily Wastewater

• main pollutants emitted into water by industry and domestic sewage

• major pollution problem due to its distinctive characteristics

Why membrane separation?

Membrane separation have

1. high oil removal efficiency

2. low energy cost

3. compact design

What type of membrane to use?

Ceramic membrane

Why ceramic membrane?

Advantages

o it has the ability to accomplish the current regulatory treatment objectives with no chemical pretreatment

o higher fluxes

o resistance to mechanical, thermal, and chemical stress allows better recovery of membrane performance

What type of ceramic membrane?

Alpha-Al2O3

o chemically very inert

o usable in pH range of 1 to 14

o no limitations in temperature and pH when using standard membrane cleaners

o produces lower refluxes as compared with zirconia and ZrO2 based on past studies

Operating Parameters

TMP

CFV Temp

Permeate Flux

TOC Removal

Fouling Resistance

OBJECTIVE

Materials

Ceramic Membrane

• Tubular ceramic membrane

• Pore size of 0.2 micron

• With a stainless steel housing

Process Feed

• Outlet of the API unit of Tehran refinery was used as a feed

• The feed was taken daily and used immediately

• Original temperature = 25-30oC

• Characterization was required to ensure existence of oil emulsion

• Drop size was below 20 microns, which indicated emulsified oil in water mixture

Pilot System

• Has three loops in the system (main, backwashing, and chemical washing loop)

• Main Loop – cross flow MF processing as it started from TK-101

• The P-101 pumps the feed from TK-101 to the bottom of the membrane module and was fed to the membrane channels

• Cross flow configuration

Pilot System

• Carried out in a total recycle mode of filtration, where retentate and permeate were continuously recirculated into the feed tank by using V-03 and V-01

• Feed concentration remained virtually constant

• Backwashing Loop – contained a backwashing tank (TK-02)

Pilot System

• Hot distilled water was used as a backflash from TK-102 using P-102

• V-104 was opened to send hot water into the membrane from the permeate side

• Chemical cleaning was used if recovery of permeate flux is necessary

• To start cleaning, TK-103 was filled with chemical agents and pumped towards the membrane using P-101.

Pilot System

• There was a heater and coil of cooling water to control temperature

• Two analog flow meters in the way of feed and permeate streams

• Tank Volume = 90 L

• TMP = 0.75-1.75 bar

• CFV = 0.75-2.25 m/s

• Temperature = 35-40oC

Method

Placement of membrane in module

Stablization of membrane

• measurement of pure water flux

Introduction of oil emulsion in tank

•Pre-heated to a desired temp

• Adjustment of operating pressure & CFV

Measurement of permeation

•Using a flow meter

Rinsing of the system

Experimental

Procedure

Experimental

Procedure

• Difference between the steady-state pure water fluxes was taken as a measure of the membrane fouling tendency • Each run consisted of: forward filtration time: 280 s backwashing filtration time: 15 s rest time: 5 s

Membrane Cleaning

The membrane was cleaned and regenerated between subsequent runs as follows, after every 90 min. operation: Rinse with clean and hot water Clean with an alkaline cleaner

Cleaning procedure: first 10 min. with a closed permeate outlet 20 min. with an opened permeate outlet temperature: 75 – 80 degC

Membrane Cleaning: Backwashing

• Membrane is hydraulically backwashed with hot water ( high pressure with a max. value of 2 bars for 15 s) • reversed-flow: to flush the membrane pores from the permeate side; releasing of retained materials in pores

Membrane Cleaning:

Chemical cleaning

• used when flux was decreased to 40 – 50% of its original value • chemical solutions were prepared in chemical tank • added chemicals depend on the material to be flushed out: to remove organic scales: NaOH solution @ 70 – 80 °C

to remove inorganic scales: Citric acid solution @ 70 – 80 °C

Wastewater Analysis

• TOC estimation using TOC Analyzer (Model DC-190) • Oil and grease content values were estimated using the FTIR spectrometer set to scan 2930 /cm TOG/TPH Analyzer Infracal (USA) Wilks Enterprise

Wastewater Analysis

• TSS values were analyzed by the procedure outlined in the standard methods (ASTM 2540D) using Whatman 2.5 cm GF/C-Class Microfiber • water sample was filtered through a pre-weighed filter. •The residue retained on the filter was dried in an oven at 103–105 °C until the weight of the filter became constant.

Wastewater Analysis

• Calculation of TSS TSS (mg/L)=([A−B]*1000)/C Where A = End weight of the filter B = Initial weight of the filter C = Volume of water filtered

Wastewater Analysis

• Turbidity values were estimated using a Turbidimeter (Model 2100A HACH) • Droplet size distribution of the emulsified oil in water was estimated using Laser Light Scattering (LLS) Method using LLS instrument (SEMATech laboratory — SEM-633)

Important parameters in MF

• Permeate flux • TOC removal efficiency • Fouling resistance

Permeate Flux

Each membrane has a special unique resistance which depends on its pore size and other properties. This resistance known as Rm, can be calculated using the initial flux of deionized water (Jwi) according to the following equation:

Permeate Flux

The resistance observed after feed filtration can be calculated using flux of deionized water after fouling and washing with water (Jww). This resistance is known as Rf and is the hydraulic resistance of the surface adsorption and pore plugging and is calculated using the following equation:

Oil Removal Efficiency

The oil removal efficiency can be evaluated according to the value of TOC removal efficiency (RTOC), which is defined as:

Where TOCfeed is TOC concentration in the feed and TOCpermeat is TOC concentration in the permeate (mg/L).

Results & Discussion

Effect of TMP

Effect of TMP

• Higher TMP results in droplets to pass rapidly through the membrane pores, so more oil droplets accumulate on the membrane surface and consequently in the membrane pores, leading to membrane fouling

Effect of TMP

Effect of TMP

•For TMP above 1.25 bar, oil and grease droplets can pass through the membrane pores and so TOC removal efficiency decreases; TMP above 1.25 bar is not appropriate for a high effluent quality • increasing TMP increases Rf severely (more tendency to cake/gel on membrane surface resulting in Rf growth)

Effect of CFV

Effect of CFV

• Increasing CFV promotes turbulence and mass transfer coefficient. • increasing CFV up to 2.25 m/s increases permeate flux and simultaneously decreases fouling resistance • At higher CFV, high shear rate and turbulence sweep the deposited particles away from the membrane surface; therefore, the fouling layer on the membrane surface is made thinner and more natural organic matter can pass through the membrane

Effect of CFV

Effect of temperature

Effect of temperature

Effect of temperature

• has double effects on permeation flux: • increase in temp lowers viscosity, increase in permeate flux • increase in temp increases osmotic pressure, decrease in permeate flux

• increasing temp. decreases fouling resistance (higher oil solubility) • however, at higher temp, oil and grease could easily permeate, giving a lower TOC removal efficiency

Effect of temperature

• running the system at a higher temperature increases its operational costs. Based on the results, a temperature of 32.5 °C can be recommended to achieve high permeation flux at low operational costs.

Effect of backwashing

Effect of backwashing

• It is possible to recover 95% of the original flux by backwashing; continues backwashing removes oil and particulates that block membrane pores • However, as the operation goes on, more severe fouling is observed since oil and particulates that pass through the ceramic membrane are adsorbed and accumulate within the porous ceramic membrane

Effect of backwashing

• For a very long operation, it is not effective for flux restoration; a flux decline of up to 40% of original flux was observed. • Chemical cleaning should be used to regenerate the ceramic membrane.

MF versus biological treatment method

Conclusion

Conclusion

MF process was more preferred and can replace the conventional biological method for the treatment of API effluent of Tehran Refinery.

The results showed that the optimum parameters for the said treatment are:

– TMP: 1.25 bar

– CFV: 2.25 m/s

– Temperature: 32.5 o C.

Analysis of the MF process shows decline of oil and grease content of 85%, TSS of 100% and 98.6% of Turbidity.

To remove reversible fouling, Backwashing process was applied. Periodic Backwashing prevents the flux to decline and the results show that it can possibly recover 95% of the original flux.

However, when the permeate flux was reduced to 40 to 50% of its original value, a chemical cleansing is required for a long term operation.

Conclusion

THE END Thank you for listening!