** Shares of De.mem DEM.AX rise as much as 14.6% to A$0.011, their highest level since September 22

** Stock marks its biggest intraday pct rise since August 13

** The wastewater treatment business acquires specialty chemicals supplier Core Chemicals for A$3 million ($1.94 million)

** About 4.6 million shares change hands, 34 times the 30-day avg

** Stock is down 19.2% YTD, including the session's moves

($1 = 1.5461 Australian dollars)

(Reporting by Anjali Singh in Bengaluru)

((anjali.singh2@thomsonreuters.com;))