 A period of 1 week shall be allowed for stabilisation (intake of water into the concrete). 

 Water levels shall be measured by approved means at 24 hours intervals for a test period of 7 days. 

 During the test period the total permissible water level drop, after allowing for evaporation and rainfall, shall not exceed 1/500 of the average water depth of the full tank or 10 mm, whichever is the more. 

The testing procedure shall be used also for small chambers (flow confluence or distribution chambers) and for manholes of gravity pipelines. 

Notwithstanding the satisfactory completion of the above test, any leakage or soaking visible on the outside face of the tank walls shall be stopped, after allowing for self-sealing. Any caulking or making good of cracks in the concerned wall section shall, where practicable, be carried out from the inside face. 

Adjacent internal chambers within a structure shall be tested sequentially in case the treatment process allows for emptying of the respective chamber independently of the whole structure. Then chambers adjacent to the chamber under test shall be empty during the test. 

## 4.19.3 Trial operation (running-in and process proving) 

Once the pre-commissioning and commissioning tests have been completed to the satisfaction of the Engineer, wastewater shall be introduced into the plant according to the start-up programme. 

The Contractor shall operate and maintain the plant in accordance with the draft operation and maintenance manuals for a trial period of approx. three months. During this period, the Engineer shall have the opportunity to witness all operation and maintenance activities, the objectives of which are to optimize the function and operation of the entire plant. 

Before starting the trial operation the Contractor shall, at his own cost, ensure that all tanks are filled with consumables and if necessary, provide seeding sludge to start-up the process. 

Activated sludge shall be produced within this 3 months period as per the conditions explained in the below paragraph. 

The plant shall be operated under automatic and manual control as directed by the Engineer to prove the functionality and reliability of the control systems. 

The Contractor shall run the plant and monitor the performance during the trial operation. The Contractor shall ensure that the treated effluent complies with the required effluent standards at least for 7 consecutive running days. After that The Contractor informs the Engineer that the plant is ready for the Test on Completion. 

In order to demonstrate that the constructed wastewater treatment plant conforms to the herewith Employer’s Requirements and the performance guarantees provided by the Contractor as a part of the Contract, the Contractor shall carry out performance tests in accordance with the following requirements: 

## General 

