Changes

When the pit is full there are several options. If there is space, the pit can be filled with soil and planted with a fruit orornamental treecan be planted, which will thrive in the nutrient rich environment (D.1), as in the [[Fill and Cover - Arborloo|Fill and Cover]], and a new pit built. This is generally only possible when the superstructure is mobile. Alternatively, the Faecal Sludge that is generated from the Collection and Storage/Treatment Technology has to be removed and transported for further treatment. The Conveyance Technologies that can be used include [[Human-Powered Emptying and Transport]] (C.2) for solid sludge or [[Motorized Emptying and Transport]] (C.3) for liquid sludge. A vacuum truck can only empty liquid faecal Sludge.

When the Faecal Sludge is thinner, it must be emptied with a vacuum truck. As the Faecal faecal Sludge is highly pathogenic prior to treatment, human contact and agricultural applications should be avoided. When it is not feasible to empty the full pit, (Semi-) Centralized Treatment can be omitted and the pit can be filled and covered with a suitable material for decommissioning ([[Fill and Cover - Arborloo|Fill and Cover]]). The decommissioned pit can be planted with a fruit or flowering tree since it will thrive in the nutrient rich environment.

Faecal Sludge that is removed can be transported to a dedicated Faecal faecal Sludge treatment facility (T.13-T.17)([[Sedimentation - Thickening Ponds]], [[Unplanted Drying Beds]], [[Planted Drying Beds]], [[Co-composting]], [[Anaerobic Biogas Reactor]]).

In the event that the treatment facility is not easily accessible, the Faecal faecal Sludge can be discharged to either a [[Sewer Discharge Station]] or a [[Transfer Station (Underground Holding Tank)|Transfer Station]](C.7). From the Sewer Discharge Stationthere, it will be transported to the Faecal treatment facility by a motorized vehicle (C.3). A technology selection tree for faecal Sludge treatment plants is transported by the sewer provided in Strande et al., 2014 (see Sector Development Tools, p. 9). (Semi-) Centralized Treatment technologies (T.1-T.17) produce both Effluent and Sludge, which may require further treatment prior to Use and is /or Disposal. For example, Effluent from a faecal Sludge treatment facility could be co-treated with the Blackwater flowing wastewater in the sewer network (Technologies: [[Anaerobic Baffled Reactor]], [[Anaerobic Filter]], [[Waste Stabilization Pond| Waste Stabilization Ponds]], [[Aerated Pond]], (T.5) or Constructed Wetlands (T.7-T.9) such as a [[Free-Water Surface Constructed Wetland]], a [[Vertical Horizontal Subsurface Flow Constructed Wetland]], or a [[Trickling FilterVertical Flow Constructed Wetland]], [[Upflow Anaerobic Sludge Blanket Reactor]], [[Activated Sludge]]).

The Faecal Sludge from the Sewer Discharge station is released either directly into the sewer or at timed intervals. If sludge is introduced directly into a sewer, there must be enough water to adequately dilute and transport the sludge to the treatment facility. From the Transfer Station the Faecal Sludge must be transported to a dedicated Faecal Sludge treatment facility ([[Sedimentation - Thickening Ponds]], [[Unplanted Drying Beds]], [[Planted Drying Beds]], [[Co-composting]], [[Anaerobic Biogas Reactor]])) by a [[Motorized Emptying and Transport|motorized vehicle]].

All (Semi-) Centralized Treatment Technologies produce both Effluent and Faecal faecal Sludge, which require further treatment prior to Use and/or Disposal. Technologies for the Use and/or Disposal of the treated Effluent include [[Irrigation]], [[Aquaculture Ponds]], [[Floating Plant (Macrophyte) Pond|Macrophyte Pond]] or [[Water Disposal - Groundwater Recharge|Discharge to a water body or Recharge to groundwater]]. After adequatetreatment, Sludge can either be used in agriculture (D.5) or brought to a Storage/Disposal site (D.12).

This system is best suited to rural and peri-urban areas where there is appropriate soil for digging and absorbing the Effluent from the pit. This system should be chosen only where there is either space to continuously dig new pits or when there is an appropriate manner of emptying and disposing of the Faecal Sludge. In dense urban settlements, there may not be sufficient transportation or access to empty or move to another pit. This system is also best suited to areas that are not prone to heavy rains or flooding, which may cause the pits to overflow. Some Greywater in the pit may help degradation, but excessive additions amounts of Greywater may lead to quick fillingof the pit and/or excessive leaching. All types of Dry Cleansing Materials can be discarded into the pit, although they may shorten the pit life and make it more difficult to empty. Whenever possible, Dry Cleansing Materials should be disposed of the pitseparately.

This system is one of the least expensive to construct in terms of capital cost. However, the maintenance costsmay be considerable, depending on the frequency and method of pit emptying. If the ground is appropriate andhas good absorptive capacity, the pit may be dug very deep (> 5m) and can be used for several years withoutemptying (up to 20 or more years). However, the groundwater level and use should be taken into considerationwhen digging pits in order to avoid contaminating it. Although different types of pits are common in most parts of the world, a well -designed pit-based system with appropriate transport, treatment and use or disposal, is still very rare.