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Evaluation of FBF Organics, BAT X236 application to SCOT tannery effluent treatment system.

This report discusses the application of BAT X236, by FBF Organics (FBF), to the wastewater treatment plant at Scot tannery. The tannery treatment plant is an activated sludge system consisting of an aeration pond, clarifier and treated effluent holding dam. The final effluent is discharged to the municipal sewer. The plant receives an average daily flow rate of ~140kl/d with a relatively high COD concentration (~9000mg/l).

BAT X236 is a group of organic molecules (bio-surfactants and enzymes) generated through a microbial fermentation process. Empirical observations have shown higher rates of organic degradation, increased metabolic rates, reduction in hydrogen sulphides and mercaptan production amongst others. Importantly in the activated sludge process, a reduction in excess of 40% has been observed in the waste activated sludge.

In order to improve the functioning of this plant, Scot tannery requested FBF Organics to introduce their BAT X236 to the effluent process. This report discusses the success of the FBF Organics application from January 2005 to December 2007.

Methodology
Water samples were collected each month from the aeration pond and the municipal dam and submitted for analysis to Talbot Laboratories (SANAS accreditation No. TO122). The treatment performance of the ponds was assessed based on: suspended solids removal, chemical oxygen demand (COD) reduction, nutrient removal (ammonia), pH and odour reduction.

Results and Discussions

COD
From January 2005 to December 2007, the aeration pond and holding dam showed a decreasing trend in COD (Figure 1a). The average monthly COD concentration in the aeration pond decreased by 24% over the sampling period, from 10377mg/l in 2005 to 7917mg/l in 2007. The dam concentrations decreased by 44% from 723mg/l in 2005 to 412mg/l in 2007 (Figure 1c). Thus the COD reduction from influent to effluent shows an improvement (Table 1) at an average of 1% reduction per year. The greatest increase during the sample period was in 2007.

Graph of COD concentrations
Year Avg COD Reduction

* 2005 92.2%
* 2006 93.3%
* 2007 94.8%

Table 1 – Annual COD Reduction
The reduction in the aeration tank could be the result of a reduced COD discharge from the tannery, however the municipal dam shows a greater reduction. This indicates that the treatment system is running more efficiently, and this efficiency continues to increase with time.
The COD concentration in the aeration basin shows fluctuations from ~4,000mg/l to ~22,000mg/l throughout the year. Periods of exceptionally high COD have the greatest percentage reduction and demonstrate that the plant coped with shock loads. This is indicated by only minor variations in COD concentration (~1102mg/l) in the dam (Figure 1a).

annual COD average

Oxygen Absorbance (OA)

The oxygen absorbed values of both the aeration pond and the dam indicates that the effluent system is currently within municipal discharge limits and improving with time. The consistency of this reduction between the 2 sample points shows that the system is capable of dealing with large fluctuations in influent COD concentrations without adverse effects.

The improved reduction in oxygen absorbed and COD values clearly indicates that the water quality is improving, even under periodic shock loading conditions.

Suspended solids
There is a 27% reduction in the TSS of the final treated effluent in the holding dam (Figure 3b). This is a result of the improved effectiveness of the clarifier in terms of solids separation, as well as reduced TSS load. The improved suspended solids balance reflects the effectiveness of the FBF Organics BAT X236 in enhancing process performance

3_copy

pH
pH values significantly vary throughout the year with no obvious trend. There is a slight decreasing trend in pH over the 3 year sample period at both sample points. Further to this, the municipal dam has a higher annual average pH, averaging 7.5 in 2007 compared to 7.3 in the aeration pond (Figures 4a and 4b).

Odours
Odours were monitored on site and reported complaints noted. No sulphide or mercaptan related odours were recorded or communicated from the public.

Conclusion
In conclusion the application of BAT X236 has considerably improved the performance of the Scot Tannery treatment system. The water quality is improving and the plant is robust and capable of coping with shock loads. With the application of BAT X236 the trends indicate performance will continue to improve and the treated effluent quality will comply with municipal discharge standards.
oxygen absorbancy values

References
• Grady, C.P, Jr., Daigger, G.T., and Lim, H.C. 1999. Biological Wastewater Treatment. Marcel Dekker, New York
• Sotirakou, E., Kladitis, G., Diamantis, N., and Grigoropoulou, H. 1999. Ammonia and phosphorus removal in municipal watewater
treatment plant with extended aeration. Global Nest: the International Journal 1 (1): 47-53.

 

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