Advances in Textile Waste Water Treatment: The Case for UV-Ozonation and Membrane Bioreactor for Common Effluent Treatment Plants

in Tirupur, Tamil Nadu, India.

S.Eswaramoorthi1, K.Dhanapal and D.S.ChauhanEnvironment With People's Involvement & Co-ordination in India

Coimbatore, India.

Introduction

Textile waste water treatment for industrial reuse remains as a complicated problem due to several reasons. Among them are 1) High Total Dissolved Solids (TDS) content of the waste water; 2) Presence of toxic heavy metals such as Cr, As, Cu, Zn, etc.; 3) Non-biodegradable nature of organic dye stuffs present in the effluent; 4) Presence of free-chlorine and dissolved silica. Thus, any adopted treatment system, especially with respect to primary treatment, should be able to address all these issues.

Segregation of dye bath and wash water, which was adopted earlier under conventional physico-chemical treatment (lime ferrous treatment for achieving flocculation) is not an viable option to recover water for industrial reuse due to the fact that the highly concentrated dye bath can not be passed into reverse osmosis membrane system utilized to recover water. Thus, for achieving desired results, the dye bath is combined with wash water and then the combined waste water is treated.Many technological advancements were made for treating textile waste water. Of most importance is the primary treatment where BOD, COD, TSS, colour, and pH are reduced/adjusted to desirable extend in order to make the effluent suitable for subsequent treatment by the reverse osmosis system that shall recover water for reuse.

As far as textile waste water treatment is concerned, colour removal and reduction of BOD/COD are the main problems to be addressed in the primary treatment. Most commonly utilized primary treatment processes are i) conventional physico-chemical treatment; ii) conventional biological treatment where continous aeration is carried out to reduce BOD; iii) chlorination; iv) ozonation (with/without ultra violet irradiation. Recent advancements, however, made the adoption of ozonation with/without ultra violet irradiation and Membrane Bioreactor as the most suitable alternatives. Due to cost and energy considerations, though UV/Ozonation and MBR technologies were develped over decades and effectively utilized in various kinds of industries, only now it has become possible to adopt them for textile waste water treatment.

1 Presently with ECP CONSULTING, www.ecpconsulting.in

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Effluent Generation Process

Effluent is generated under various processes during textile wet processing. These major processes include i) bleaching; ii) neutralising; iii) washing; iv) dyeing; v) washing; vi) acid wash; vii) washing; viii) soaping; ix) hot wash; x) fixing and softening. The list of chemicals used in bleaching and dyeing are presented in Table-1.1 and Table-1.2.

Table-1.1: List of chemicals used in bleaching.

Chemical Utilization (per 100 kg of cloth)

Soft flow machine Winch

Wetting agent 0.5 kg 0.5 kg

Caustic soda 2.5 kg 4.0 kg

Peroxide 3.0 kg 4.0 kg

Lubricants 0.2 kg 0.3 kg

Stabilizers 0.2 kg 0.3 kg

Peroxide killer (oxidizing agent) 1.0 kg 1.0 kg

Acetic acid 2.0 kg 2.0 kg

Table-1.2: List of chemicals used in dyeing.

Chemical Utilization (per 100 kg of cloth)

Soft flow Winch

Lubricants 0.3 kg 0.4 kg

Sequestering agent 0.6 kg 1 kg

Dye stuff 150 g for light shade.1.5 kg for medium shade.10 kg for dark shade.

150 g for light shade.1.5 kg for medium shade.10 kg for dark shade.

Soda ash Light shade - 6 g/L; Medium shade – 11 g/L;Dark shade – 20 g/L

Light shade - 6 g/L; Medium shade – 11 g/L;Dark shade – 20 g/L

Sodium chloride Light shade – 15 g/L; Medium shade – 45 g/L;Dark shade – 90 g/L

Light shade – 15 g/L; Medium shade – 45 g/L;Dark shade – 90 g/L

Acetic acid 2.5 kg 3.0 kg

Soap 1.0 kg 1.0 kg

Fixing 1.0 kg 1.0 kg

Softener 2.0 kg 2.0 kg

The selection of dye by member units shall depend upon the type of fibres being dyed, desired shade, dyeing uniformity and fastness (stability or resistance of colourants to influences such as, light, alkali,

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etc.). Reactive dyes are normally used by most of the members while disperse and direct dyes are also used sometimes. Sulphur and Vat dyes are only rarely utilized. Some of the brand names of the dyes being used by the member units is given here:

1) Procion dyes.2) Remazol dyes.3) Drimarene dyes.4) Solophynyl dyes.

For 100 kg of cloth, the volume of water added in the dye bath shall be 800 L in the case of soft-flow machines, and 1500 L in the case of winch.

The main pollutants generated by bleaching includes chlorinated organics, BOD, COD, oxidizing agents, alkali and acids. Dyeing process generate many pollutants viz., salts, surfactants, levellers, lubricants, alkali, volatile organics, cleaning solvents, stabilizers, catalysts, grease resisting agents, exhausting agents, soaping agents, softeners etc., apart from the unfixed dye in the bath, which is let out after dyeing operation is over. The typical raw effluent characteristics of textile waste water are presented in Table-1.3.

Table-1.3: Typical raw effluent characteristics of the textile waste water

Parameter RangepH 6 - 10Temperature 35-45°CTotal dissolved solids 8,000 –12,000 mg /LBOD 300 – 500 mg/LCOD 1000 – 1500 mg/LTotal suspended solids 200 – 400 mg /LChloride 3000 –6000 mg/LFree chlorine <10 mg /LSodium 70 %Trace elements ligands (Fe, Zn,Cu,As,Ni ,B, F, Mn,V, Hg, PO4, CN)

<10 mg/L

Oil & grease 10 – 30 mg/LTNK (as-N) 10 - 30 mg /LNO3 -N < 5mg/LFree ammonia < 10 mg/LSO4 600 –1000 mg/LSilica < 15 mg/L

With due considerations to the raw effluent characteristics given in Table-1.3, the following parameters require much attention with regard to implementing a good waste water treatment scheme.

i) pH

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ii) Biological Oxygen Demand (BOD)iii) Chemical Oxygen Demand (COD)iv) Total Dissolved Solids (TDS)v) Total Suspended Solids (TSS)vi) Hardnessvii) Sodiumviii) Chlorideix) Free Chlorinex) Trace elements & ligands (Fe, Zn ,Hg, Cr, Cu, Se, As, CN free ammonia etc.xi) Oil and greasexii) Silica

Conventional Technologies & Constraints

There are mainly two technologies which are normally utilized for textile waste water treatment. 1) Conventional physico-chemical treatment (with lime and ferrous); 2) Conventional biological treatment with aeration. These two technologies have the following problems associated with them.

While conventional biological treatment is best suited for primary treatment, due to the following reasons it can not be successfully implemented for textile wastewater treatment:

1) High TDS content retards microbiological growth. This is due to the fact that high concentration of solutes results in high osmotic pressure that prevents efficient transfer of water into the cell. If biological growth is retarded, then the efficiency of the treatment system to bring down the BOD is affected.

2) Presence of toxic heavy metals also prevents biological growth. Though microbiological organisms are able to grow under textile waste water, their growth shall become limited as the concentration of heavy metals rises due to recycling of biological cell materials.

3) The most common problem with textile waste water treatment is that most of the dye stuffs are non-biodegradable which renders conventional biological treatment ineffective or less efficient.

The Case for UV-Ozonation

Table-1.4: Major components and processes of the proposed treatment system.

S.No Treatment process Treated parameters

1

Primary treatment with aeration, homogenization, advanced oxidation (UV-Ozonation) and ultrafiltration.

Colour removal.Rejection of fine particles.BOD/COD reduction, removal of suspended solids (TSS).

2Double stage reverse osmosis system Water recovery for reuse.

Rejection of salt and organics (BOD/COD).

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S.No Treatment process Treated parameters

3Multiple Effect Evaporator with thickener and centrifuge. Water recovery from R.O., reject – for

reuse.Separation of salt.

4 Sludge drying bed Filtration of sludge from clarifier.

5Solar evaporation pond1 Evaporation of effluent resulting from

cleaning up of Multiple Effect Evaporator.

Full description on the criteria employed for designing the treatment system is provided in the following paragraphs.

Since chlorination will result in the production of carcinogenic chloro-organic compounds, ozonation is preferred. Also, the rate of oxidation of organics with ozonation is around 30 times faster than chlorination; and ozonation in combination with UV irradiation yields several benefits viz., i) the rate of degradation of organic contaminants under UV-Ozonation is several orders of magnitude greater than with chlorine; therefore, retention time required to achieve desired results could be minimized, which reduces power consumption and operating costs. ii) secondly, ozonation of the effluent in combination with UV has the capability to destroy heavy molecular hazardous substances, which are typical of textile wet processing waste water. iii) finally, ozonation when combined with UV increases the treatment efficiency and reduces overall operation cost. Ozonation also oxidizes most of the trace elements in the raw effluent, which are flocculated and settled before they reach reverse osmosis system.

In the textile effluent, the main hazardous substance is the dye stuff. In the adopted treatment system, ozonation combined with UV irradiation breaks up the heavy dye molecules into small non-toxic form. In addition, a significant portion of the dye stuff could be oxidized due to ozonation and UV irradiation, where upon highly reactive hydroxyl and super oxide radicals are produced and sustained for a prolonged period, which strongly reacts with the dye stuff and oxidises it very fast. Thus the hazardous dye stuff is mostly degraded by the UV-Ozonation, thereby de-colourizing the effluent, and minimizing the hazardous waste output from the treatment system in the form of reject.

Though ozonator alone is sufficient to treat the effluent for reducing BOD and COD load, UV is also employed to improve the overall efficiency of the system. Combined application of ozone and UV radiation leads to an increase in the concentration of oxidizing agent, including strongly reacting hydroxyl radicals, due to interaction between the products of water radiolysis and those of ozone decomposition. This is reflected in the higher decomposition efficiency of organic pollutants (BOD/COD) contained in the waste water.

1 Multiple Effect Evaporator shall be cleaned on daily basis, resulting in the generation of 200 L of effluent per day. Since mother liquor from Multiple Effect Evaporator shall be recirculated to the 3-effect forced circulation evaporator, and the decant from sludge drying bed shall be returned to equalization tank, provision for solar evaporation pond is to treat only the effluent generated by washing of evaporator. The estimated solar evaporation pond size is 100 m2, which shall be able to evaporate 400 L of effluent on normal sunny days. Extra capacity is provided to evaporate the entire effluent on cloudy days [Evaporation rate under normal conditions is 4 mm/m2 as prescribed by TNPCB].

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Finally, ozone generation could be controlled very easily. This ensures that only optimum power is utilized in the treatment process.

The proposed treatment scheme uses UV in combination with ozone (called Critical Point Radiation) for the destruction of the dye stuff and other molecules in the effluent. The mechanism of UV-Ozone oxidation is described below:

UV photolysis of ozone in the aqueous phase yields hydrogen peroxide followed by reaction of the conjugate base, hydroperoxy anion (HO2

-) with ozone to yield superoxide (O2- ) and hydroxyl radical.

O2 + H2O + h* -----> O2 + H2O2

H2O2 + H2O -----> H3O+ + H2O-

O3 + HO2- -----> O2 + *O2

- + OH*

Superoxide reacts with ozone to form hydroxyl radicals:

O3 + *O2-+ H2O -----> 2O2 + OH- + OH*

The hydroxyl radical enters a competing reaction with ozone to form more superoxide according to the following reaction:

O3 + OH* + H2O -----> O2 + H3O+ + *O2-

In the absence of organic compounds, the first three equations are the initiation reactions, with the next two steps of reactions representing the chain photo-decomposition of ozone. However, in the presence of sufficient or, excess organic compounds ( > 100 mole), the hydroxyl radical abstracts one hydrogen atom to form water molecule and an organic radical.

OH* + RH-----> H2O + R*

This is, in turn, followed by reaction between the organic radical and oxygen to yield organic peroxy radicals:

R* + O2 -----> RO2*

These organic peroxy radicals could either photolyze to more stable organic molecules or, regenerate further superoxide which re-enters the system by reaction with ozone via the following equation:

O3 + *O2-+ H2O -----> 2O2 + OH- + OH*

Repetition of the above process will ultimately lead to complete destruction of the organic compound. Here, the oxidant (ozone) concentration directly determines the concentration of hydroxyl radicals, therefore, the speed of the reaction.

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Process implementation

UV-Ozonation is generally more effective at basic pH. High pH values tend to generate more hydroxyl radicals which shall increase the oxidation capacity of the ozonation system. Further, when metals are present in the waste water and the pH is in the alkaline range, dissolved metals in the effluent may form soluble or, insoluble metal hydroxides upon ozonation (Thus, ozonation also helps to remove heavy metals present in the solution). Since the raw effluent pH shall always remain basic (pH > 7), there shall be no need to adjust the pH. In order to remove insoluble metal hydroxide and other precipitates, a clarifier is provided after ozonation.

Pilot plant tests

The pilot plant has been designed for treating 200 m3/day (10 m3/hr) and commissioned at a textile dyeing unit in Erode. The plant has been commissioned on 26th September 2006. Pilot plant tests were conducted by M/s.Canadian Crystalline Waters (India) Pvt. Ltd., Chennai, and experimental parameters are given here in Table-1.5 along with the results in Table-1.6

Table-1.5: Effluent and system parameters for pilot plant test runs.

Parameter Value

Effluent characteristics (Inlet)

Flow rate 10 m3/h

TDS 10, 460 mg/L

TSS 196 mg/L

pH 10.2

System characteristics

UV dose 30 mW.cm-2.sec-1

Contact tank volume 5 m3

Number of contact tanks 2

Ozone output from one generator module 320 g/h

Total output of ozone from 2 modules 2 x 320 = 640 g/h

Ozonation methodology Multi point injection & fine bubble diffusion

Ozonator specifications

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Parameter Value

Output of oxygen concentrator (feed to ozonator) 1 m3/h

Output of ozone/m3 of oxygen 320 g/h

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Table-1.6: Pilot plant test results

Timemin.

Initial COD(C - mg/L)

Ozone dose (mg/L)

Final COD(Co – mg/L)

- ln (C/Co)

25 930 106.7 99 2.240

35 930 149.3 132 1.952

50 465 213 72 1.865

Calculation of ozone consumption and scale-up

The ln [O3 dose] values are plotted against ln (C/Co) were plotted [using linear regression function in Casio fx-991 MX scientific calculator] to derive the steady-state concentration of dissolved ozone in the waste water (given by intercept A = 4.725 mg/L) and ratio of oxidized contaminant to that of ozone (given by slope B = - 0.540). The minus sign before the slope (B) indicates that as the ozone concentration increases, the contaminant concentration in the waste water decreases. From these data, the ozone dose required to achieve desired reduction in COD could be estimated using the following equation:

d (mg/L) = A ln (Co/C)1/B

Required dose (d) = A * ln (CODinitial /CODfinal)1/B

= 4.725 mg/L * (1300/160)1/0.540

= 229 mg/L

However, not all the ozone supplied is get transferred, and 80-90% of transfer efficiency is normally achieved in waste water treatment. To be on the safer side of the design, 80% transfer efficiency is assumed. Thus, the required dose can be estimated using the following formula:

D = d (100/80) = 229 * 100/80 = 286 mg/L

The Case for Membrane BioreactorThe pilot plant studies are based on secondary data available in the public domain. The selection of MBR is justified on the following lines:

1) Membrane Bioreactor is an advancement over the conventional activated sludge process with the use of ultrafiltration or, microfiltration membrane, which helps to maintain high levels of MLSS concentration and better treated water quality.

2) Activated sludge process has been well documented, thoroughly experimented, and widely adopted for the treatment of industrial waste water, including that of textile waste water.

3) While conventional biological treatment systems may face problems due to:

a. Low F/M ratio (due to low levels of BOD in the raw effluent);

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b. Sludge settleability in the clarifier;

c. Growth of algae due to higher levels of total dissolved solids in the raw effluent;

d. Increased operating costs due to low levels of MLSS concentration, increased aeration tank size, requirement for higher retention time;

e. Inability to withstand shocks, i.e., sudden changes in the raw effluent quality;

f. Requirement for more secured land fill area due to higher levels of sludge production;

g. Inefficient nutrient removal in the raw effluent that shall encourage growth of microbial organisms on the reverse osmosis membrane;

h. Poor treated water output quality which shall impose operational restrictions on the secondary treatment system,

all these issues are properly addressed and taken care by the Membrane Bioreactor as already described in earlier paragraphs.

Due to its design MBR shall be able to handle effluent with wide ranging characteristics, especially with respect to COD and BOD. Due to the maintenance of high levels of Mixed Liquor Suspended Solids (MLSS), i.e., from 10,000 mg/L to 15,000 mg/L, the BOD and COD values are brought down drastically and due to the utilization of membrane and higher biological activity, the variations in the physico-chemical characteristics of the outlet water are largely smoothed out.

Membrane Bioreactor utilizes activated sludge process in combination with membrane filtration (microfiltration or, ultrafiltration) for retention of active micro-organisms and heavy molecular weight organics typical of textile effluent, where after BOD and colour are reduced, and then the effluent is let out for further treatment.

The MBR has two zones i) anoxic and ii) oxic. The bacteria growing under anoxic condition has the capability to break down recalcitrant macromolecules1, which is then digested by the aerobic bacteria in another zone. In this way, a significant portion of the dye stuff could be broken down. Thus the hazardous dye stuff is mostly degraded.

Due to the use of membrane and high concentration of active micro-organisms, the MBR treated water has a uniform physico-chemical characteristics and the colour is mostly reduced, making this suitable for further treatment by the reverse osmosis system2. Due to reduction of colour in the feed, the reject from the R.O system shall also be less coloured, thereby the recovered salt can be reused. In this way, hazardous waste generation is minimized and at the same time salt is also recovered3.

1 Earlier works in this direction are given under References.2 Whether the MBR output shall be coloured or not shall also depend on the nature of the dye in the raw effluent.

However, a significant part of colour shall be removed by MBR, while the traces of it shall be successfully eliminated by the activated carbon filter adopted in the design.

3 Only if the feed to the R.O system is colourless, then the reject shall be colourless. Otherwise, the reject shall have colour, resulting in coloured crystallized salt, which could not be reused. Unlike the conventional biological treatment system, use of MBR reduces the colour significantly and the remaining colour, if any, shall be removed by activated carbon filter as already mentioned. Thus, MBR provides a better opportunity to recover colourless salt from the evaporator for industrial reuse apart from so many other advantages.

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i) While conventional biological treatment system shall be useful for treating effluents with high BOD and COD, the nature of the textile effluent makes this scheme unsuitable for adoption. Since the colour of the textile effluent should be removed in order to recover clear salt, simple biological oxidation schemes may not be worth full.

ii) Secondly, the dyes are mostly non-biodegradable and only a part of it is biodegradable. Due to their chemical nature, even the biodegradable dyestuff remains recalcitrant. The ability to digest recalcitrant macromolecular dye stuff is exhibited by anaerobic bacteria Thus, anoxic biological degradation is an important step if we consider biological treatment. Even then, the recovered water shall have colour, which will get rejected by the reverse osmosis system and that shall be finally passed onto the salt crystallized by the post-evaporation system built with the evaporator. Thus, a technology which utilizes anaerobic digestion along with membrane filtration for colour removal is essential to recover reusable salt.

iii)Chlorination will result in the production of carcinogenic chloro-organic compounds, which shall heavily impact on the environment.

iv)Ozonation can be considered as a suitable alternative. The rate of oxidation of organics with ozonation is around 30 times faster than chlorination. Ozonation in combination with UV (advanced oxidation) is more effective in destroying the organics present in the effluent; the reaction time of ozone with organics present in the effluent is also several orders of magnitude higher.

v) However, the quality of effluent received from Membrane Bioreactor is more stable than what could be achieved with ozonation, enabling the optimal functioning of the secondary treatment system. This stabilized output water quality is due to the prevalence of a steady-state condition inside the MBR compartments1, whereby both the anaerobic and aerobic bacteria shall flourish, feeding on the digestible organic matter available in the effluent. Since the micro-organisms are retained within the MBR tank by filtration through the use of membranes, a high biological activity is maintained. The maintenance of high biological activity renders a uniform output from the MBR and at the same time, the retention time of the effluent could be minimized.

vi)Further, when the food/micro-organisms ratio is low, the settleability of the sludge is increased2. This is because, under low food/micro-organisms ratio, the micro-organisms are under food-limited environment, even though the rate of metabolism may be high when the recycled micro-organisms are first mixed with the incoming waste water. Once food is limiting, the rate of metabolism rapidly declines until the micro-organisms are in the endogenous respiration phase with cell lysis and re-

1 The stable output from MBR is mainly due to re-circulation of waste water from the membrane zone into the anaerobic and aerobic compartments, and the maintenance of high MLSS concentration. If X is the inflow, and therefore outflow, anaerobic to aerobic and, aerobic to membrane flow is 4X, with a recirculation from membrane compartment to anaerobic being 3X to balance. When ever the feed quality changes, its characteristics are dampened by this re-circulation as the feed water get diluted by the re-circulating fluid, and any oscillations in effluent parameters are dampened by 3 times. This is valid only for parameters having linear relationship with concentration viz., BOD, COD, TDS, etc. For parameters having logarithmic relationship with concentration, for example pH, this relationship shall be more complicated – but still the changes in such parameters due to variations in effluent quality shall be dampened. Similarly, higher MLSS concentration level helps to dampen the changes in BOD and COD within a short residence time due to intense biological activity.

2 Gray, N.F. (1999) Water Technology: An introduction for Environmental Scientists and Engineers, First Indian Edition, Viva Books Private Limited, New Delhi, pp.548.

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synthesis taking place3. Therefore almost complete oxidation of substrate occurs producing a high-quality effluent, low BOD, good flocculation and sludge settlement.

vii)Food limitation is mainly dependent on the amount of food available (which is given by flow x BOD = organic loading) and the amount of biomass available in the digestion chamber. Thus, for a given BOD level in the effluent, if the number of number of micro-organisms per unit volume is kept high by recycling of sludge, then BOD reduction shall be kept at higher side – and at the same time the settleability of the sludge shall also be increased.

viii)While MBR is utilized, the microbial activity remains high due to their retention by the membrane. Thus, a low food/biomass ratio is maintained, leading to higher BOD removal and good sludge settleability. Even if the sludge fails to settle down, the MBR membrane blocks the suspended flocs (biomass) from leaving the digester. In the case of conventional biological treatment, sludge retention is mainly dependant on the settleability of the sludge.

The advantages of using MBR are:1) Hydraulic Retention Time (HRT) and Solids Retention Time (SRT) can be changed fairly

independent of each other.

2) Lower HRT (8-10 hrs) compared to conventional process (15-28 hrs). This reduces tank volumes.

3) High MLSS concentration in MBR (8,000-15,000 mg/L) allows more BOD throughput than conventional process which has 1500-3000 mg/L MLSS.

4) Smaller footprint per unit BOD loading or per unit feed flow rate. Ideal for expansion of existing facilities without increase in footprint. Land for MBR is about half or less compared to conventional process.

5) Submerged MBRs more suitable for retrofits using existing aeration tanks/clarifier.

6) MBRs operate at low F/M3 ratio and long SRT. This means less sludge generation. Some MBRs operate at zero sludge generation. This reduces costs of sludge disposal.

7) Low F/M ratio operation minimizes oxygen consumption since microbes are in endogenous respiration phase and not in growth phase.

3 Endogenous respiration shall consume more amount of oxygen due to recycling of carbonaceous material inside the MBR compartments, thereby increasing operating costs. However, it shall reduce the quantity of generated sludge as most of the recalcitrant substances are degraded due to increased SRT. Optimization techniques utilizing mathematical modelling shall provide the required F/M ratio suitable to achieve better effluent quality and minimize sludge production. But, this shall be possible only after the plant is commissioned and operated for a certain period of time to collect necessary data – as effluent quality plays a certain role in determining the operating parameters.

3 Food to micro organism ratio – an important parameter to be maintained in the activated sludge process so that optimal TSS removal could be achieved while maintaining necessary level of MLSS concentration. Changes in F/M ratio shall affect the settleability of sludge in the clarifier. But in the MBR, due to the retention of micro organisms, F/M ratio can be lowered without concern on settleability. Due to higher SRT and high levels of MLSS, endogenous respiration takes place, resulting lesser sludge production. Also, the need for clarifier is also eliminated. This is one of the main advantages of MBR over to that of conventional activated sludge process.

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8) Better sludge quality eliminates sludge bulking.

9) Post treatment such as sand-filtration is not necessary. Membranes provide final barrier for pathogens and suspended solids.

10) Effluent quality is more suitable for use as feed to reverse osmosis for desalination for process.

11) Process control is easier and more amenable to automation. No more clarifier upsets or, Total Suspended Solids carry-over.

12) Eliminates loss of slow-growing nitrifying bacteria to clarifier weirs. Improves nitrification.

13) Better removal of phosphorus associated with suspended solids (bacteria and colloids).

14) The need for secondary clarifier is eliminated.

The Membrane Bioreactor shall reject total suspended solids in addition to reducing BOD/COD to the desired levels, making the effluent suitable for further treatment with reverse osmosis system.

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References

General details on advanced oxidation processes and as it is applied in textile waste water treatment are available from:

1) Handbook: Advanced photochemical oxidation processes. United States Environmental Protection Agency, Office of Research and Development, Washington, DC. EPA/625/R-98/004.

2) Engineering and Dosing: Ultraviolet/Chemical Oxidation, Department of Army, U.S.Army Corps of Engineers, Washington.

Literature on the use of MRB for textile waste water treatment

Badani, Z., Ait-Amar, H., Si-Salah, A., Brick, B., and Fuchs, W. (2005) Treatment of textile waste water by membrane bioreactor and reuse. Desalination, 185: 411-417.

Hai, F.I., Yamamoto, K., and Fukushi, K. (2005) Different fouling modes of submerged hollow-fiber and flat-sheet membranes induced by high strength waste water with concurrent biofouling. Desalination, 180: 89-97.

Hai, F.I., Yamamoto, K., and Fukushi, K. (2006) Membrane coupled fungi reactor – An innovative approach to bioremediation of hazardous dye wastewater. Environmental Sciences, 13(6): 317-325.

Hai, F.I., Yamamoto, K., and Fukushi, K. (2006) Performance of newly developed hollow fiber module with spacer in integrated anaerobic-aerobic fungi reactor treating textile wastewater. Desalination, 199: 305-307.

Hai, F.I., Yamamato, K., and Fukushi, K. (2006) Development of a submerged membrane fungi reactor for textile waste water treatment. Desalination, 192: 315-322.

Lopez, C., Mlelgo, I., Morelra, M.T., Feijoo, G., and Lema, M. (2002) Enzymatic membrane reactors for biodegradation of recalcitrant compounds. Application to dye decolourisation. Journal of Biotechnology, 99(3): 249-257.

Lourenco, N.D., Novals, J.M., and Pinheiro, H.M. (2001) Effect of some operational parameters on textile dye biodegradation in a sequential batch reactor. Journal of Biotechnology, 89(2-3): 163-174.

Jin, D., Hia, F.I., and Yamamoto, K. Development and application of anaerobic membrane bioreactor systems in the far-eastern countries. Submitted as a part of literature review for the project “Membrane Bioreactors for Anaerobic Treatment of Conventional and Medium Strength Wastewater”, funded by WERF (Project No.02-CTS-4).

Hai, F.I., Fukushi, K., and Yamamoto, K. (2003) Treatment of textile wastewater: Membrane bioreactor with special dye-degrading microorganism. Proceedings of the Asian Waterqual 2003, Bangkok, Article # 2Q3F16.

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Gao, M., Yang, M., Li, H., Yang, Q., and Zhang, Y. (2004) Comparison between a submerged membrane bioreactor and a conventional activated sludge system on treating ammonia-bearing inorganic wastewater. Journal of Biotechnology, 108(3): 265-269.

Zheng, X., and Li., I.X. (2004) Printing and dyeing waste water treatment using combined process of anaerobic bioreactor and MBR. Huan ling Ke Xue, 25(5): 102-105 [article in Chinese; PubMed index: 15623033].

Lubello, C. and Gori, R. (2004) Membrane bioreactor for advanced textile waste water treatment and reuse. Water Science and Technology, 50(2): 113-119.

Lubello, C., and Gori, R. (2005) Membrane bioreactor for textile waste water treatment plant upgrading. Water Science and Technology, 52(4): 91-98.

Malpei, F., Bonomo, L., and Rozzi, A. (2003) Feasibility study to upgrade a textile waste water treatment plant by a hollow fibre membrane bioreactor for effluent reuse. Water Science and Technology, 47(10): 33-39.

You, S.J., Tseng, D.H., Liu, C.C., Ou, S.H., and Chien, H.M (2006) The performance and microbial diversity of a membrane bioreactor treating with the real textile dyeing wastewater. IWA World Water Congress, Beijing, China. e-mail contact: siyou@cycu.edu.tw

Yun, M-A, Yeon, K-M., Park, J-S., Lee, C-H., Chun, J., and Lim, D.J. (2006) Characterization of biofilm structure and its effect on membrane permeability in MBR for dye waste water treatment. Water Research, 40(1): 45-52.

De Wever, H., Lemmens, B., Roy, V., and Diels, L. (2004) Optimisation of biological textile waste water treatment. Proceedings of the European Symposium on Environmental Biotechnology, ESEB. e-mail contact: heleen.dewever@vito.be

Hai, F.I., Yamamoto, K., Fukushi, K. (2007) Hybrid treatment systems for dye wastewater. Critical Reviews in Environmental Science and Technology, 37(4): In press.

W. Liu, J.A. Howell, T.C. Arnot & J.A. Scott (2001). A novel extractive membrane bioreactor for treating biorefractory organic pollutants in the presence of high concentrations of inorganics: application to a synthetic acidic effluent containing high concentrations of chlorophenol and salt. Journal of Membrane Science, 181(1) 127-140.

Lin, Y., Tanaka, S., and Kong, H. (2006) Characterization of a newly isolated heterotrophic nitrifying bacterium. Water Practice & Technology, 1(3), IWA Publishing doi: 10.2166/WPT.2006052.

Trussell, R.S., Merlo, R.P., Hermanowicz, S.W., and Jenkins, D. (2006) The effect of organic loading on process performance and membrane fouling in a submerged membrane bioreactor treating municipal waste water. Water Research, 40: 2675-2683; Corrigendum to “The effect of organic loading on process performance and membrane fouling in a submerged membrane bioreactor treating municipal waste water” [Water Research, 40 (2006) 14].

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Research Projects - European Union Funded Projects on MBRMany research projects are funded by the European Union to carry out research on utilization of MBR for the treatment of waste water. These projects are listed below (details available in the attachments):

1) 5th Framework Programme

a. Poseidon

b. P-THREE

c. AQUAREC

2) 6th Framwork Programme

a. AMEDEUS

b. EUROMBRA

c. Reclaim Water

d. Removals

e. INNOWATECH

3) Marie Curie Actions

a. AQUAbase

b. MBR-TRAIN

4) INCO Program

a. MBR-RECYCLING

b. EMCO

c. PURATREAT

5) Program Asia Pro-Eco II

a. AsiaBioMem

6) CRAFT Program

a. IWAPIL

7) Collective Program

a. Space2tex

8) COST Action

9) DU-LIFE Program

Space2tex: Wastewater recycling in textile finishing through the application and further development of membrane bio-reactors used in space life-support systems. Fifth Framework Programme Collective Research. Project URL: http://www.dappolonia-research.com/space2tex

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Purification of textile waste water by MBR. Project URL: http://www.a3-gmbh.com e-mail contact: steffen-richter@a3-gmbh.com

European Union Project – Puratreat: http://www.puratreat.com

Membrane bioreactors for anaerobic treatment of conventional and medium strength wastewater. http://www.civil.ubc.ca/faculty/Berube/AnMBR.html

Sung, S.-W., and Ugurlu, A. (2004-2006) Application of anaerobic membrane bioreactor for waste water treatment. Funded by National Science Foundation, USA.

Mishoe, G.L. (1999) F/M ratio and the operation of an activated sludge process. Florida Water Resources Journal, March.

Comments on this article can be forwarded to chitraeswar@gmail.com

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