Digester

The digesters are the heart of the foul sewage treatment system in Morton. Great brick lined chambers beneath the ground where the sewage is warmed to blod heat and allwed to ferment - a process which turns the noxious effluvia of thousands into the much sught after Nightsoil . The process also generate a flammable gas which is used to heat the material and drive the pumps that lift the treated water back to the surface.

Discovery

The hazards of storing cess in closed spaces had long been known but how this had come to be turned to th profitable benefits of the digesters is unclear. As with many technologies there are stories told that take on lives of their own and the best known versions are often far from strict historic truth. Historians with access to the Gongsters' archives and who have taken the trouble to investigate the stories told by the Drakiss believe that shortly after the first long tunnels to route it more than a mile downstream of the town the flooding of a drakiss colony chamber with cess. The chamber was sealed for this was before the development of the pumps now used and there was no means of raising such a massive quantity of material.
Some time later the pressure had built up to the point that the gas began to leak through the seals and, knowing the risks of explosion, the drakiss and the gongsters tapped the chamber and list the gas as it emerged - this prevented explosions, but extra shafts needed to be sunk to supply air and it was through these than most of the gas was eventually vented to atmosphere.
When the gas was gone, and the area had cooled they cautiously opened the chamber and, after ventilating it, found that the cess had been transformed. Many years of debelopment were needed to bring this from an interesting observation to a usable technology - the most important elements were developing the burners and calorifiers to heat the cess and devising sustems that could operate continuously, rather than in huge batches.

Operation

The digester is made up of 4 types of unit. One screen and preheater are enough to supply several sets of chambers and filters - and indeed it must be arranged so, rather than scaling up the chambers as once a month or so each chamber and filter need to be taken out of use for cleaning.

• The Screen - The first step in the process is the screening of the sewage to remove large solids, or break them down to be small enough not to interfere withthe subsequent mechanisms.

• Preheater - the raw sewage is warmed by a combination of the residual heat from the treated water and gas burners fueled by the gas produced by the digester itself. This warms it from ambient temperature to around human body heat.

• The Chambers - the sewage is fed into the min digestion chambers where it follows a circuitous route over an under a series of baffles. As it makes it's way through the Chambers, the sewage is digested by the "essence". It is important to regulate the flow so that itspends long enough in the chambers for the digestion to complete and that a portion of the partly digested material is fed back into the beginning of the chamber otherwise it will gradually be washed out of the system.

• The Filters - the digested sewage is then passed through a filter of sand, gravel and stone to remove any remaining solids.

If the system is being correctly operated the treated sewage will now be well on the way to being safe to drink. The final step of the process sees it fed into an area of wetland from which it emerges almost as pristine as before before it met the town.

Access & Availability

The digesters are a closely guarded trade secret of the Gongsters and the Morton Drakiss. Though a number of towns and cities have begun to press for information on how Morton manages its waste the knowledge currently remains restricted to these tight circles. The wider use of it is a major topic of debate and division among the Gongsters - at some point it will get out and the two questions are of when, and whether the gongsters will remain in control of it when it does.

Production of Nightsoil

Once a month or so each set of chambers is taken out of service - drained down and the accumulated sediment from the chambers and the filters is removed. This sludge is alowed to dry by piling it up to drain and then sold as fertiliser to the local farmers and market gardeners or loaded onto barges for trade with other towns.

On the "Essence"

The physical infrastructure is highly impressive, but as nothing to the power of the "essence" that powers the digestion. What it is and how it works are not known but the Gongsters and the Morton Drakiss have learned much over the years abut how to ge the most from it.
Firstly, it is important to keep many of the trade wastes of Morton's industries away from the system - this is the reason for the separate trade sewer system, for this will destroy the essence. Secondly, although left to itself sewage will digest, adding the essence dramtically increases the speed with which this happens, an this essence is something which is found in the cess of the drakiss. This "secret ingredient" is almost certainly why the attempts of other towns to aquire the technology have not been successful even when they have got the other basics right.