1. Introduction
S-10 is a flood mitigation river water holding pond in Penang, Malaysia. Drain water from Georgetown is channeled into this 150m x 85m x 2 m deep retention pond before being discharged into the sea. Excess water in the pond is either drained into the sea during low tide by opening the tidal gate or through mechanical pumping when sea level is higher than the pond water level. The retention pond prevents ingress of salty seawater into Georgetown and allows free flow of surface drain water during heavy rain that coincides with high sea water level.

The drain serves as drainage for discharge of ground surface water during heavy rain, as well as discharging of grey water from commercial, industrial and domestic sewerage wastewater. Discharge of untreated grey water forms the bulk of the water flowing into the pond on dry days. The influent water pollution level is significantly diluted during heavy rain. Influent BOD range from 40 mg/l to 250 mg/l and that of COD has a low value of 100 mg/l to as high as close to 1,000 mg/l. The influent water also carries a very high concentration of suspended solid and floating debris.

Most of the floating debris is trapped at the grit chamber just before the pond entrance and physically removed regularly. There is a high concentration of suspended solid that have settled into the pond as bottom sludge. The pond has accumulated a bottom sludge exceeding half meter within one year of operation. If left untreated, the pond would be fully filled with bottom sludge within a few years and become incapable of serving its intended function as a flood mitigation pond.

In addition to bottom sludge built up problem, extreme bad odor emanating from the pond has affect nearby residence, which has become a significant problem for the Jabatan Pengairan Dan Saliran Negeri (JPS). JPS has also expressed interest in bring down the pollution level to below Standard B before discharging into the sea to prevent harm to marine life. Standard B specifies a BOD < 50 mg/l and COD < 100 mg/l.

1. AquaClean Remediation
The pond has an estimated volume of 25,000 m3. On dry days, the grey water from Georgetown forms the bulk of the influent water. The estimated flow rate is 5,000 m3 per day. This gives an average of five days retention time, which is ideal for biological treatment. The flow rate during heavy rain is not known, it is estimated at several times that of the normal dry day flow rate. The water in the pond can be completely replaced after a few days of heavy rain.

AquaClean ACF-32 bioremediation was carried out from 29th August 2005 to 5th March 2006. A 10 ppm inoculation was done on 29th August 2005, a day affected by heavy rain immediately after inoculation. This was followed by a 8 ppm dosing three days later and followed by 5 high enhance dosing of 4.5 ppm in the first month. Maintenance dosing was done at less than 2 ppm at 12 gallons per week for the remaining period of treatment.

AquaClean ACF-32 is a highly active liquid bioculture developed and manufactured by Ecological Laboratories Inc, USA. It consists of 29 selected microorganisms with a cell count exceeding 380 million microorganisms per milliliter. AquaClean ACF-32 is one of the most effective biological products, with proven capabilities in breaking up very difficult to degrade organic components. Application of AquaClean is simply, just open the bottle and pour the contents directly into the pond.

2. Progress Monitoring and Performance Tracking.
The extremely bad odors experienced by the workers and nearby residence were significantly eliminated within one month of treatment. The bad odor was essentially eliminated throughout the remaining treatment period in the pond area, with the exception of some bad smell near the entrance point of the pond where the water was not yet treated. The S-10 AquaClean Bioremediation Project was showcased at the National Environment Seminar on 14-16 Dec 2005, as organized by JPS in Penang. Delegates were invited to the site on 15 Dec 2005. Upon arrival at the pond near the influent area, delegates experience some bad odor, but most of them confirmed that odor was not noticeable at other parts of the pond during the visit. A water sample taken from the pond showed to the delegates indicated high transparency (low turbidity).

Water samples at the influent point of the pond and effluent point near the discharge tidal gate were taken twice a month to monitor water parameters. BOD, COD, TSS and total NH3 were measured. The sludge thickness was also measured on the day of inoculation followed by three more measurements during the treatment period. Sludge thickness was measured by means of a transparent glass tube inserted into the pond until it contacted the hard bottom to check sludge thickness. An independent laboratory conducted the water sampling and monitored the testing. The six months treatment result is tabulated below:-

JPS Penang Retention Pond Project

Water Parameter Measurements

AVERAGE SLUDGE LEVEL

4. Conclusion
There were no significant changes between influent and effluent water parameters during the first two months of treatment in August and September 2005. This is in line with the expected behavior of bioremediation. Significant water parameter improvement was observed starting in mid-October 2005. However, data would not show much improvement during periods of heavy rain when influent water pollution level was low. It was also noted that the water in the pond forms a circular motion when large volumes of water were discharged through the tidal gate or being pumped out. The influent and effluent water was well mixed by this circular motion. As such, the water in the pond became quite homogeneous and has no difference between influent and effluent water. This explains the non-performance of water parameter on 29 Nov 2005 and January 2006.

The bottom sludge continued to be reduced throughout the treatment period, and was practically eliminated by Feb 2006. The breaking up of bottom organic sludge often contributes to increasing amount of pollutants in the water as seen in the water parameters during the first two months of treatment. As the bottom sludge is reduced, we expected to see an improvement in bioremediation. This is clearly reflected in the effluent water parameters taken on 24 Feb 2006 where the discharge of BOD, COD and TSS now meets the Standard B regulatory requirement despite the pond experiencing the highest pollutant input load during the entire treatment period in Feb 2006.

Based on comparing the initial bench-mark sludge measurement with the most recent measurement made on 24 Feb 2006, an estimated 6,000 m3 of sludge has been degraded by AquaClean’s environmental friendly bioremediation process. Based on RM 80 per m3 of dredging and dumping cost, the biological sludge removal saved the Board over half a million ringgits, a very cost affective solution. In addition, AquaClean eliminated the bad odor in the surrounding area of the pond and improved the quality of the water before it was discharged into the sea.

Bottom line, AquaClean has achieved well beyond JPS’s initial targets of odor control and water quality improvement. AquaClean’s treatment significantly improved the water quality (obtaining better then Standard B), it has effectively reduced odor; and in addition has achieved a sludge reduction rate far exceeding anyone’s expectation. This sludge reduction has restored the retention pond to its intended function.

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