ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Chemical dissolution of struvite precipitates in pipes from anaerobic sludge digestion

Stanislava Kecskésová, Zuzana Imreová, Marek Martonka, and Miloslav Drtil

Department of Environmental Engineering, Faculty of Chemical and Food Technology, Slovak University of Technology, Bratislava, Slovak Republic

E-mail: stanislava.vlckova@stuba.sk

Received: 28 October 2019  Accepted: 10 February 2020

Abstract:

Prevention of struvite formation at wastewater treatment plants (WWTPs) is currently possible using several approaches. However, failure of these measures and subsequent spontaneous struvite formation may lead to serious operational problems. A similar problem occurred at a municipal WWTP with enhanced phosphorus removal and anaerobic sludge digestion, where spontaneous struvite precipitation caused clogging of the pipes with digested sludge. For direct struvite dissolution in the sludge pipes, organic and inorganic acidic solutions were investigated. It was shown that using solutions of pH < 1 complete dissolution can be reached within 1–5 days. However, the use of such strong acids was not recommended by the WWTP operator because of a corrosion hazard (old pipes and fittings not made of stainless steel). At pH 2 and 3, the use of acetic acid (CH₃COOH) solution can be considered promising. However, because of the heterogeneity of precipitates in the sludge pipes and insecure dissolution, measures for mechanical cleaning, in addition to chemical dissolution, were proposed.

Keywords: Chemical removal of struvite; Clogging of sludge pipes; Effect of pH; Inorganic acids; Organic acids

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-020-01096-3

Chemical Papers 74 (8) 2545–2552 (2020)