Studies & Test Data
STUDY: WASTEWATER SLUDGE POND NO 4
STUDY LOCATION: AUSTRALIA
STUDY DATE: March 21, 1992
OBJECTIVE: TO SIGNIFICANTLY REDUCE SLUDGE SOLIDS
PRODUCT: BIOSPAN BR90 ANAEROBIC / FACULTATIVE BACTERIAL INOCULANT
SIZE OF WASTE-WATER POND: 260 m x 140 m x 1.5 m deep (ie., approx. 50 megalitres)
In December 1991, a biological inoculation procedure was implemented at this municipal which was designed to significantly reduce sludge solids content of sludge lagoons. The inoculation program, which utilizes a revolutionary anaerobic inoculant known as Biosapn BR90, was commenced on 12/30/91 and concluded on 1/31/92, resulted in a massive 53.4% reduction in sludge solids. The procedure also succeeded in eliminating odour, as well as significantly reducing other
parameters, such as supernate BOD, SS and Ammonia.
Pond 4 is a stabilization pond for digested sludge from various sources including high strength industrial waste, septic tanks, and the adjacent Municipal Sewerage Treatment Plant. The sludge typically had the following treatment characteristics: Total Solids Residue (TSR): 7%; Fixed Residue
(FR) : 40% of TSR.
Historically ... The de-sludging (dewatering and disposal) procedure normally incurs very high capital and environmental costs. A specialized biological inoculation procedure, which has been used with tremendous success in industrial waste treatment pond applications, was offered as a very attractive and low cost option to substantially reduce the sludge solids content and thereby provide equally substantial cost savings.
The objective of the procedure was to significantly reduce the sludge solids content of the pond (by up to 40%) and thereby achieve equivalent savings in sludge dewatering and disposal costs.
Historically the sludge pond has been de-sludged every three years and data accumulated over many years indicates that the rate of buildup of sludge and the sludge depth after a set period of time, is predictable. (The population supplying the plant is relatively constant). Prior to the start of the inoculation program, an electronic sludge depth monitoring device showed that the average
sludge depth was 600mm. Subsequently during the course of the study, sludge depths were measured using a hollow perspex tube, sealing off the tube with a core of clay. This was necessary as soon after the study commenced, the sludge depth measuring device became unreliable. However, historical sludge accumulation/depth records indicate that the depth of sludge at the start of the
study would be between 580 and 620mm. The client wanted the study to indicate quickly whether BR90 would be successful as the contractor booked to de-sludge the pond in the conventional manner would not be able to do so before the seasonal heavy rains commenced. We were given 4-6 weeks to demonstrate BR90’s ability to achieve an adequate result.
SIZE OF SLUDGE POND: 260 m x 140 m x 1.5 m deep (ie., approx. 50 megalitres)
DOSING SCHEDULE & METHOD
BR90 was added to the pond via a 90,000 litre tank. Over a 32 day period, 134 Kg BR90 was dosed into the pond via the above tank, and multiplication of the bacteria in the tank was facilitated using nutrients. After the first two doses via the tank, only sewage sludge was used as nutrient, with water ex a clarifier used to “top” up the tank. Dosing commenced 12/30/91 and ceased 1/31/92.
SAMPLING AND TESTING
At the beginning of the program and during, the sludge was sampled at a depth of between 120 - 150mm from the clay bottom of the pond. Composite samples were tested from between 30 x 50 sampling points (refer enclosed date). The client also regularly tested the parameters BOD, SS, NH3, and Nitrates in the supernate above the sludge layer. Also measurements were made on the Chlorophyl A, Pheophytin A levels in the supernate to show the reduction in algae that could be achieved. E coli measurements were also performed to demonstrate the reductions in coli that
occurred through competition from the BR90 bacteria.
RESULTS: Between 12/30/91 - 2/26/92 the following results have been achieved:
SLUDGE SOLIDS 53.4% Zinc 13%
BOD Unfiltered Supernate 73% Copper 12%
BOD Filtered Supernate 79% Lead 12%
SS Supernate 63% Cadmium 20%
COD Supernate 56% Nickel 32%
NH3 Supernate 52% Chlorophyl A Supernate 74%
Sludge Depth 33% Pheophytin A supernate 75%
Chromium (Sludge) 25% E Coli Supernate 99%
NB: Dewatering of pond 4 commenced on 2/26/92.
As at 5/3/92 considerable biological activity was still evident, with vigorous bubbling and bubble/froth formation on the surface of the supernate. It was quite clear that given time, further reductions in many of the above parameters would likely occur.
No sludges were discharged to pond 4 subsequent to 24/10/91. BR90 bacterial inoculation commenced on 12/30/91 and the bacteria was tankered to pond 4 and pumped into the pond at various locations around the edge. From that time on the BR90 was pumped into one end of the pond only. In the short time given for the reduction in sludge to occur there was evidence in the sludge depth/solids profile that it would have been preferable to add BR90 at more than one point, more frequently. However, after 7 weeks, the bacteria and dispersement and sludge layer parameter distribution appeared to be becoming more uniform.
The sludge solids In pond 4 were reduced by 53.4% during the period from 12/30/90 to 2/26/92 whilst the control sample of the sludge composite taken on the commencement of the program reduced in solids by only 3.2%. All the green algae colour in pond 4 was lost within 7-8 days of the BR90 inoculation commencing.
As at 2/12/92 (point 19 on the graphs), some greenish algae colour returned to pond 4. The unfiltered BOD rose by 27 mg/l from its lowest point reached of 40 mg/l. However, the filtered BOD continued to drop to around 5-7 mg/l. The continuing aggressive biological activity meant that some suspended solids rose with the gas bubbles and continued to contribute to the unfiltered BOD. This was also confirmed by the fact that on 2/27/92, the filtered COD was 571, and the unfiltered COD was 303 and both still falling. The incoming sludges, in this location, can have very high BOD, COD and heavy metal concentration. Consequently, the relatively shallow sludge ponds presented quite a challenge to the BR90 bacteria culture.
The program of BR90 inoculation has been shown to achieve a massive 53.4% reduction in sludge solids with substantial reductions in all key parameters in both the sludge blanket and in the covering supernate, even when the conditions were not completely suited to anaerobic processes. The reduction was achieved in a very short period of time, seven (7) weeks with absolutely no odour creation. The plant reported that all of the normal unpleasant odour associated with the pond water at the commencement of BR90 dosing, was eliminated within 4-5 days of dosing commencement. It is anticipated that the remaining sludge residue will display greatly enhanced dewatering characteristics, and will remain free of unpleasant odour.