TECHNOLOGY FOCUS - CHEMICAL ENGINEERING - Preferred Method: In the moving bed-fermentation of the liquid carried out by microorganisms in the fermenter/reactor, the fermentation involves aerobic fermentation of water carried out for reducing chemical oxygen demand (COD), the microorganisms comprise any one or more selected from bacteria, fungi and other microorganisms capable of carrying out fermentation and the fermenting liquid is aerated by blower/aerator or by any other ways for improving aeration. The method involves: (a) adding a number of the devices to the water in fermenter/reactor; (b) aerating the water to achieve growth of the microorganisms on the surface of the devices available for anchorage; (c) agitating the liquid in the fermenter by a way for achieving movement of the devices in the fermenter; (d) and allowing the fermentation to proceed for a period of time required to bring down the COD load to 100 ppm or to other target level. Moreover, (a) the fermenting liquid is raw sewage or any other liquid containing fermentable organic dissolved solids, (b) the device comprises a biodegradation resistant moving bed biofilm reactor media (MBBR media) or a biodegradation resistant sachet of a fabric permeable to liquid containing dissolved solids containing within it the porous material and, optionally, float that renders the sachet moveable in the fermenting liquid when agitated, (c) the porous material comprises any one or more selected from activated carbon as granules or otherwise, saw dust of wood, chips of wood and diskettes of wood the porous material is activated carbon, (d) the way to provide the agitation/aeration is one or more selected from the group bubbling of air through the fermenter, bubbling oxygen of varying purity thorough the fermenter, using the impeller or propeller, up-flow or down-flow of liquid by pumping action or Twin lobe/centrifugal air blower used to increase dissolved oxygen level. Preferred Device: The device comprises any one or all of the following: (a) sachets which are made from a material that is permeable to the liquid in the fermenter, hold the porous material within them, and are: (i) made of a material that has a density that helps to make the sachet movable when the sachets are added to the fermenting liquid in fermenter and the fermenting liquid is agitated, or (ii) are associated with a way for adjusting the density of the sachets such that they become moveable when the sachets are added to the fermenting liquid in the fermenter and the fermenting liquid is agitated; (b) an article having surface to which the porous material is immobilized on the surface and the article having a density such that they become moveable when they are added to the fermenting liquid in the fermenter and the fermenting liquid is agitated. Also, (a) in the (a) above, the material that is permeable to the liquid in the fermenter is a fabric/paper made from synthetic polymers or any other material that has reasonably long life and reusuability in the fermenter, (b) in the (ii) above, the unit for adjusting the density of the sachets comprises a material that has a density lower than water, can be retained within the sachet, and has reasonably long life and reusuability in the fermenter, (c) the article in (b) above comprises any one or more selected from MBBR media, and a polymer foam sheet that does not absorb water when immersed in water/fermenting liquid. The material that has a density lower than water, can be retained within the sachet, and has reasonably long life and re-usability in the fermenter consists of a synthetic material or a natural material. Furthermore, (a) the synthetic material is one or more selected from the list consisting of any one or more selected from the group comprising a polypropylene foam sheet, plastic media / sheet, polypropylene non woven fabric, polypropylene non-woven filter paper, polypropylene woven film/paper/sheet having density lower than water, any color thickness shape any size and any other synthetic article that can be used as a float; (b) the natural material is one or more selected from the list consisting of painted wood pieces, wood discetts/small discs, wood chips, wooden filings, perlite, vermiculite or any naturally occurring material that can be used as a float. The device is impregnated with live bacteria required for the aerobic fermentation.