ISSN   0974-3618  (Print)                    www.rjptonline.org

            0974-360X (Online)

 

 

RESEARCH ARTICLE

 

Reduction of COD and Decolourisation of UASB spent wash using E-MBR

 

Sathish Sundararaman1*, Jagadish Kumar L1, Narendrakumar. G2

1Department of Chemical Engineering, Faculty of Bio and Chemical Engineering, Sathyabama University, India.

2Department of Biotechnology, Faculty of Bio and Chemical Engineering, Sathyabama University, India.

*Corresponding Author E-mail: sathish.chemical@sathyabamauniversity.ac.in

 

ABSTRACT:

Water reclamation is a process by which waste water from industries was processed by physical, chemical, biological or a combination of these treatments so that the water can be reclaimed or returned to the environment safely. In the ethanol production, the total volume of wastewater released is 10 times more that the ethanol produced. Currently anaerobic treatment is the most widely used to reduce COD and BOD level from the waste water. A laboratory scale External Membrane Bio reactor (E-MBR)is used to treat the distillery waste water collected from Up flow anaerobic sludge blanket (UASB) unit. The objective of the present research was to enhance the treatability of distillery effluent using MBR and was studied COD, TDS and pH changes were investigated and high treatment of distillery effluent has been achieved.  The performance of this study is evaluated based on the removal of colour, pH changes observed at various stages of this treatment process and found that maximum decolourisation of 92% and 95% reduction in COD level.

 

KEY WORDS: COD, E-MBR, reclamation, UASB, Bacteria decolorization.

 

 


INTRODUCTION:

Distilleries have been generating high quantities of effluents.  In most of the traditional methods, the treated effluent also yields very high BOD, COD, TS and TDS level with high intensity of colour(1-3). The wastewaters of a distillery consist of fermenter sludge, and spent wash. The amount of wastewater generated in a distillery depends upon the water used and the technology adopted for the manufacture of alcohol. In the conventional batch type about 10 kl of spent wash is produced per kl of alcohol. Spent wash has a temperature of about 100°C. It is highly acidic and dark brown in colour. (Table 1). Colour removal and COD reduction are of prime importance on treatment of distillery wastewater.

 

 

 

 

 

 

 

 

Received on 27.05.2015          Modified on 15.06.2015

Accepted on 20.06.2015        © RJPT All right reserved

Research J. Pharm. and Tech. 8(7): July, 2015; Page 845-848

DOI: 10.5958/0974-360X.2015.00138.9

Table 1: Characteristics of Spent wash from UASB unit.

Parameter

Spent wash (after anaerobic digestion)

Colour

Dark brown

pH

7.2

Chemical oxygen demand, mg/L

50,000 – 60,000

Suspended Solids mg/l

15000

Dissolved Solids mg/l

8000

 

Microorganism capable of both bioremediation and decolorization of molasses wastewater have been isolated from digested sludge. The effective bacterial strains from sludge was isolated and acclimatized on increasing concentrations, which were able to reduce COD without any aeration and the major products of degradation process were biomass, carbon dioxide and volatile acids. A membrane bioreactor (MBR) combines the biological degradation and the physical separation by membrane filtration(4, 16).

 

The major advantages of using a MBR process are superior organics removal, lower sludge production, effluent disinfection and high loading rate capabilities(15,24). The main objective of this work is to enhance the performance of treatment of spent wash in E-MBR.  The external membrane configuration is preferred, due to low area requirement, longer life, capable of operating at high solid concentration and low capital cost. In view of these factors, we have chosen to carry out this study by selecting an external membrane configuration system.

 

MATERIAL AND METHODS:

Sample Collection and Preservation

The spent wash was collected from a distillery unit (M/S. Padmadevi Sugars Ltd) in Kanchipuram district of Tamil Nadu. Liquid untreated effluent was collected in sterile containers and preserved at 4C.

 

Chemicals and Membrane

All the chemicals were of highest purity available and were of analytical grade, Merk, Mumbai. Hollow fiber membranes have a smaller range of pore sizes (0.01 to 0.1 micron) used which are capable of removing colour, odor, and organics removal. 

 

Enrichment and Isolation of spent wash decolorizing bacteria.

UASB sludge was used for enhancing decolorizing bacterial cultures by enrichment culture techniques. Microorganisms having the potential for decolourising spent wash were isolated by this means. Mineral Salt Media (MSM) supplemented with glucose (0.5 % w/v) and yeast extract (0.2 % w/v) ammonium phosphate (0.01% w/v), NaCl (0.02% w/v), MgSO47H2O (0.02% w/v), Sludge (1000 ppm) was used for the study5.

 

The culture flasks were incubated at 37C. After incubation a loop-full of medium was streaked onto sterile Plate count Agar and incubated at 37C for 24 to 48 h, and 1 ml of the enriched culture was transferred to fresh medium. Well grown bacterial colonies were picked and further purified by streaking. The pure cultures of individual bacterial strains were maintained by streaking on Nutrient agar slant and stored at 4C. Identification of the bacterial isolates was carried out by the routine bacteriological and 16s rRNA method (6-8).

 

Bioremediation Experiment

In our previous report we have studied the optimized coagulant dosage by using Response Surface methodology was 2 g/l of 10% poly aluminium chloride, 4 g/l of 10% Maxfloc 508 and 40 mg/l of 2% Maxfloc C22 was used for this study. The experimental setup consists of HDPE containers for feed tank followed by sand filter, activated carbon filter, micron cartridge filter, membrane bioreactor, membrane module fitted with a suitable pump.  The supernatant solution obtained after flocculation was fed into filtration units so that the units can be operated in a nominal pressure range of 2 – 3 kg/cm2.The effluent from the feed tank was connected to a feed pump (20-30 liters per hour) and the discharge of the pump is fed to a sand filter.  The sand filter is a cylindrical vessel made up of PP housing that contains various sizes (pebbles, gravels, coarse and fine) of sand.  The outlet from the sand filter is connected to a 5 micron cartridge filter to filter the suspended particles that are present in the sand filter outlet. The outlet from this cartridge filter is fed to an activated carbon filter containing granular activated carbon made out of coconut shell carbon having an iodine number of more than 1000 mg/g and particle size of 4 x 16 mesh.  The outlet from the carbon filter is connected to 1 micron cartridge filter for filtering out the fine suspended particulates that are passing out.  Then it is connected to an External membrane MBR system, which contains a hollow fiber membrane made up of poly sulphone / poly ether sulphone. The final clear outlet from this membrane module which is often termed as permeate is collected at a rate of 10-15 liters per hour continuously(Fig. 1), the feed fed to the reactor at 35 - 40°C to get optimum decolorization(9,10,17).

 

Instrumental analysis

Intensity of colour was measured by checking the OD values of the test solutions.  Except filtered water samples, supernatant and coloured samples were centrifuged prior to determination of absorbance for eliminating the hindrance due to suspended particles in the sample.  The supernatant was diluted and the absorbance was measured using UV-Visible spectrophotometer at the λmax of 530nm. 

 

The removal of colour was evaluated in terms of reduction of absorbance from the original waste water in comparison with the supernatant and the outlet samples collected from subsequent units. All experiments were performed in triplicate. The percentage of decoloration was calculated according to the formula below:

 

 

Where, Ao is the initial absorbance at time ‘t = 0’; At is the absorbance at any time ‘t’

 

Total solids and COD determination

The COD of the wastewater sample and the treated samples are done by IS: 3025 – Part 58:2006 standards. The effluent was characterized for reduction in chemical oxygen demand (COD) before and after the biodegradation. The COD of the effluent was measured by using automated COD analyzer. The total organic carbon (TOC) was measured using Hach DR 2700 spectrophotometer. The removal of organic carbon was evaluated in terms of reduction of carbon value from the original waste water in comparison with the supernatant and the outlet samples collected from subsequent  units(11-14).

 

RESULTS AND DISCUSSION:

The isolated organism were purified and 16s rRNA sequencing and identified as Bacillus licheniformis, Bacillus funiculus and Pseudomonas aeruginosa. The organism was subjected for clustal W and multiple sequence alignment was done to investigate the similarity between the sequence and the result shows a higher order of similarity among them.  There was a massive reduction in the color was observed after microbial treatment(17-21).

 

COD of the influent and effluents at each stage of units were monitored. When run at 33% dilution of spent wash COD of effluent was reduced by 90% from the initial raw spent wash. For 66% and 100% spent wash it reached 95% (Table 2). Similarly the intensity of colour at the each unit outlet was decreasing gradually, for 33% dilution 87% decolourisation was observed (Fig.1) and for 66% and 100% dilution decolourisation was found to be 90% and 92%(Table 3).

 


 

Table 2: Percentage COD removal of UASB Spent wash at various outlet streams.

Dilution Rate

(%)

Percentage Reduction in COD Values (%)

UASB Spent wash after dilution

Sand Filter Outlet

Cartridge Filter Outlet

Permeate

33

36.4

60

72.7

90.5

66

49.1

66.4

80

93.2

100

54.5

72.7

85.3

95.4

 

Table 3 Percentage decolourisation of UASB Spent wash at various outlet streams.

Dilution Rate

(%)

Percentage Decolourisation (%)

UASB Spent wash after dilution

Sand Filter Outlet

Cartridge Filter Outlet

Permeate

33

Dark Brown

29

53

87

66

Dark Brown

33

63

90

100

Brown

40

76

92

 

 

 

Fig.1

 

 

 

 


The main objective of the study was to use anaerobic digested sludge for the isolation of effective microorganism to treat spent wash along with EMBR to reduce COD and colour from the UASB spent wash(22,23). The COD of the raw spent wash was found to be around 55,000 mg/l which was reduced to 3,000 mg/l thus giving an overall COD removal efficiency of 90 - 95% and 87 – 92% of decolourisation at the end of the whole cycle of process for various dilution rates (Fig 2, 3).


 

Fig. 2 Percentage decolourisation of UASB Spent wash at various outlet streams.

 

 

Fig. 3 Percentage COD removal of UASB Spent wash at various outlet streams.

 

 

Thus the objective of COD reduction and decolourisation of UASB spent wash was achieved by the methodology mentioned above along EMBR using the effective microbial consortia of Bacillus licheniformis, Bacillus funiculus and Pseudomonas aeruginosa. But still it is recommended to conduct a pilot scale study to verify the lab scale efficiencies are achieved.

 

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