A filter unit (100, 200, 300, 400) for filtering microparticles from a feed liquid containing microparticles, the filter unit (100, 200, 300, 400) comprising: a filter chamber (101, 201, 301, 401) extending along an axis, and comprising opposing first end and second end walls (101a, 201a, 301a, 401a, 101b, 201b, 301b, 401b) and at least one sidewall (101c, 201c, 401c, 401d) extending therebetween, wherein both first and second end walls (101a, 201a, 301a, 401a, 101b, 201b, 301b, 401b) are coincident with the axis, a filter cage (102, 202, 302, 402) contained within the filter chamber (101, 201, 301, 401) and configured to rotate about the axis, the filter cage (102, 202, 302, 402) comprising one or more than one filter media (103, 203, 303) for filtering microparticles from the feed liquid; an inlet (104, 204, 304, 404) configured to pass feed liquid through the first end wall (101a, 201a, 301a, 401a) into the filter chamber (101, 201, 301, 401); an outlet (105, 205, 305, 405) in the filter chamber (101, 201, 301, 401) for passage of filtered liquid out of the filter chamber (101, 201, 301, 401); a drive shaft (107a, 207a, 307a, 407a) configured to drive rotation of the filter cage (102, 202, 302, 402), the drive shaft (107a, 207a, 307a, 407a) extending from the first end wall (101a, 201a, 301a, 401a) of the filter chamber (101, 201, 301, 401) to the filter cage (102, 202, 302, 402); wherein the second end wall (101b, 201b, 301b, 401b) is or comprises an opening (106b, 206b, 306b, 406b) therein and a removable lid (106a, 206a, 306a, 406a), in a first configuration the opening (106b, 206b, 306b, 406b) is closed by the removable lid (106a, 206a, 306a, 406a) so that feed liquid cannot pass through the opening (106b, 206b, 306b, 406b), in a second configuration the lid (106a, 206a, 306a, 406a) is removed from the opening (106b, 206b, 306b, 406b) so that filtered microparticles are extractable from the filter chamber (101, 201, 301, 401) through the opening (106b, 206b, 306b, 406b); and wherein the drive shaft (107a, 207a, 307a, 407a) comprises a mechanical connection to a drive means, and said drive means is an electric motor. a filter chamber (101, 201, 301, 401) extending along an axis, and comprising opposing first end and second end walls (101a, 201a, 301a, 401a, 101b, 201b, 301b, 401b) and at least one sidewall (101c, 201c, 401c, 401d) extending therebetween, wherein both first and second end walls (101a, 201a, 301a, 401a, 101b, 201b, 301b, 401b) are coincident with the axis, a filter cage (102, 202, 302, 402) contained within the filter chamber (101, 201, 301, 401) and configured to rotate about the axis, the filter cage (102, 202, 302, 402) comprising one or more than one filter media (103, 203, 303) for filtering microparticles from the feed liquid; an inlet (104, 204, 304, 404) configured to pass feed liquid through the first end wall (101a, 201a, 301a, 401a) into the filter chamber (101, 201, 301, 401); an outlet (105, 205, 305, 405) in the filter chamber (101, 201, 301, 401) for passage of filtered liquid out of the filter chamber (101, 201, 301, 401); a drive shaft (107a, 207a, 307a, 407a) configured to drive rotation of the filter cage (102, 202, 302, 402), the drive shaft (107a, 207a, 307a, 407a) extending from the first end wall (101a, 201a, 301a, 401a) of the filter chamber (101, 201, 301, 401) to the filter cage (102, 202, 302, 402); wherein the second end wall (101b, 201b, 301b, 401b) is or comprises an opening (106b, 206b, 306b, 406b) therein and a removable lid (106a, 206a, 306a, 406a), in a first configuration the opening (106b, 206b, 306b, 406b) is closed by the removable lid (106a, 206a, 306a, 406a) so that feed liquid cannot pass through the opening (106b, 206b, 306b, 406b), in a second configuration the lid (106a, 206a, 306a, 406a) is removed from the opening (106b, 206b, 306b, 406b) so that filtered microparticles are extractable from the filter chamber (101, 201, 301, 401) through the opening (106b, 206b, 306b, 406b); and wherein the drive shaft (107a, 207a, 307a, 407a) comprises a mechanical connection to a drive means, and said drive means is an electric motor.