A method for inhibiting silica scale formation in an aqueous system comprising adding an anti-scalant to water used in the aqueous system, wherein: the water has a pH of less than 9.5, the aqueous system comprises a reverse osmosis system including a reverse osmosis membrane, wherein the method comprises the steps of: adding the anti-scalant to a source of feed water containing silica, and passing the resulting feed water through the reverse osmosis system such that a portion passes through the reverse osmosis membrane to produce a permeate stream having a reduced concentration of silica with the remaining portion of feed water forming a reject stream having a higher concentration of silica, and wherein the anti-scalant comprises a tertiary amine-terminated polyoxyalkylene represented by: wherein Y and Y' are independently selected from hydrogen or alkyl; R 1 is selected from a C 1 to C 20 hydrocarbon moiety; R 2 is selected from a C 4 to C 20 hydrocarbon moiety; and E is a terminal end group selected from hydrogen, alkyl, -NR 1 R 2; L is a linking group selected from a direct bond between the oxyalkylene repeating unit-(CH 2 CH O)- and the nitrogen atom, or a C 1 to C 20 hydrocarbon moiety; n is an integer from 2 to 1000; and m is an integer from 0 to 1000. the water has a pH of less than 9.5, the aqueous system comprises a reverse osmosis system including a reverse osmosis membrane, wherein the method comprises the steps of: adding the anti-scalant to a source of feed water containing silica, and passing the resulting feed water through the reverse osmosis system such that a portion passes through the reverse osmosis membrane to produce a permeate stream having a reduced concentration of silica with the remaining portion of feed water forming a reject stream having a higher concentration of silica, and wherein the anti-scalant comprises a tertiary amine-terminated polyoxyalkylene represented by: wherein Y and Y' are independently selected from hydrogen or alkyl; R 1 is selected from a C 1 to C 20 hydrocarbon moiety; R 2 is selected from a C 4 to C 20 hydrocarbon moiety; and E is a terminal end group selected from hydrogen, alkyl, -NR 1 R 2; L is a linking group selected from a direct bond between the oxyalkylene repeating unit-(CH 2 CH O)- and the nitrogen atom, or a C 1 to C 20 hydrocarbon moiety; n is an integer from 2 to 1000; and m is an integer from 0 to 1000. adding the anti-scalant to a source of feed water containing silica, and passing the resulting feed water through the reverse osmosis system such that a portion passes through the reverse osmosis membrane to produce a permeate stream having a reduced concentration of silica with the remaining portion of feed water forming a reject stream having a higher concentration of silica, and wherein the anti-scalant comprises a tertiary amine-terminated polyoxyalkylene represented by: wherein Y and Y' are independently selected from hydrogen or alkyl; R 1 is selected from a C 1 to C 20 hydrocarbon moiety; R 2 is selected from a C 4 to C 20 hydrocarbon moiety; and E is a terminal end group selected from hydrogen, alkyl, -NR 1 R 2; L is a linking group selected from a direct bond between the oxyalkylene repeating unit-(CH 2 CH O)- and the nitrogen atom, or a C 1 to C 20 hydrocarbon moiety; n is an integer from 2 to 1000; and m is an integer from 0 to 1000.