19/208 - Ringsend WwTP – Digestion Capacity Increase

Tender description

Irish Water is currently upgrading the Ringsend WwTP, which treats most wastewater arising in the Greater Dublin Area (GDA), based on the application of aerobic granular sludge technology (Nereda®). The capacity of the upgraded WwTP will be approximately 2.4 Million Population Equivalent (PE), with 1 PE assumed to be 60 g BOD/day. Consequently, the existing sludge line needs to be upgraded to accommodate the increased load. The upgrade of the existing sludge line will involve upgrades to the existing thermal hydrolysis plant, modifications to the existing digesters and other ancillary works in the sludge treatment buildings. This PIN relates to the modification of the digesters only. The other works will be delivered by a Main Contractor appointed by Irish Water. This project will provide only for the increase of mesophilic digestion capacity. It will specifically provide for increasing the digestion capacity by employing a known and proven process within the existing 4 digesters - each with a capacity of 4,360m3. The digesters treat a mixture of primary and secondary sludges, normally pre-treated using CAMBI® thermal hydrolysis. The existing tanks must be modified alternately without interrupting the current digestion process. The process proposed must be proven and capable of digesting the aforementioned sludge streams at a capacity of c. 200 tds/d (peaking at 225 tds/d) at c.11% tds. The pre-treatment system must not be modified. Proposed processes that comprise the dosing of reagents and/or enzymes are not considered acceptable Any proposed process and controlling system will have been proven at full scale with similar feedstock over one year of successful operation at a scale of 10 tds/d. Further systems commissioned above this scale will enhance this proposal. The process shall provide stable digester operation at a Sludge Retention Time (SRT) of 6-8 days at average and peak conditions. (As per PIN Documents)