A Successful Chemical Cleaning of Struvite Scale Prologs the Life Span of Sludge Exporting Pipeline

In this paper, a successful experience of cleaning struvite-fouled sludge exporting pipeline is presented. Acid cleaning of 14 inches (350 mm) diameter 5,000 ft (1,515 m) long sludge exporting pipeline, carried out at the San Jose Santa Clare Water Pollution Control Plant (SJ/SC WPCP), San Jose, CA, demonstrated the viability and cost effectiveness of the method. Diluted hydrochloric acid (3-5% by volume) mixed with proprietary dispersants, corrosion inhibitors and foam suppressants were used in the cleaning process. In highly coordinated cleaning operations, Progressive Environmental Services (PES), Portsmouth, VA was able to complete the work in 5 days. The acid cleaning effectively removed the struvite scale (2.5-3 inches—62.5-75 mm) to almost the bare metal, thereby restoring the functionality of the pipe and saving the City of San Jose over one million dollars in new pipe replacement costs.