Hello, and welcome to this module on waterless pit based systems. In this module we're gonna discuss three different system templates that are similar because they're all based on pit technologies that are mostly waterless. The first system is called the "Single Pit System". Unsurprisingly, it's based on a single pit. So moving from left to right and starting with the products, we note that the two main products are urine and feces, as they have the thick lines attached to them. The other products are optional, or not necessary depending on the system, but we'll have to consider those as we move forward. The first question we're presented with is whether to choose a dry waterless toilet or a pour flush toilet. The choice will depend on whether or not there is water available, but also whether or not there are the resources and capacities to build up the necessary infrastructure that comes later. It's important to note that although we build up the system from left to right, it is often necessary to revise your choices, and so, the process can become quite iterative. The key element of this system is the single pit. Either a basic pit or a VIP, Ventilated Improved Pit design. In both cases sludge will be produced, so the quality of this sludge will vary, of course, depending on the user interface chosen, the amount of water used, the lining of the pit, and the soil conditions. You can see on the diagram that the sludge, once it arrives for treatment, will be split into two fractions: the treated sludge, and the effluent. Looking at this system template is both interesting and important because the first half, the dryer toilet, plus a single pit, is very, very common in most parts of the world; however, as we have discussed before, the second half of this system, the transport, treatment and uses of the products becomes quite complicated, involves a lot of technical components, and potentially very difficult decisions. The lesson here is to never assume that a single pit system is a simple system. System two: "Waterless Pit System Without Sludge Production". seems from the name that it might be quite simple, but in fact, it is complicated by the variety of products. This system is based on the idea of alternating pits, so either a double VIP or a <i>fossa alterna</i>. You can see that organics, shown here on the left, is an optional product, but it's not optional if a composting chamber is chosen for the collection and storage technology. If the double VIP or the <i>fossa alterna</i> is chosen, no additional organics are needed. The quality of the product that emerges will, of course, be different so the type of end use goals you will have will influence the collection and storage technology that you choose and of course, the availability of the organics as well as the willingness to add them and the need to use the final product. This application goal will essentially determine your choices. This is the template for the classic urine diversion system. It is interesting to look at this template because it's not very straightforward. There are multiple flow paths to take into account, and parallel technologies that need to be designed. Bear this in mind when you hear that Ecosan or waterless sanitation technologies are called simple. The individual technologies may be, but this system certainly is not. In fact, we can see from this template that although the actual toilet, the urine-diverting toilet may be simple, there are numerous parts and products to consider. Also, because the system is waterless, the gray water must be considered separately. Whereas in other systems it could be simply mixed in with the gray water, here it remains entirely separate through the duration of the process. This system is not necessarily complicated to build, but it certainly requires careful planning, especially in terms of how to use the final products, so the stored urine and the dried feces, and determine how they can be either applied or disposed of. Here is a photo from Durban, South Africa, where you can see a whole community with urine-diverting dry toilets. Take a minute and see if you can identify where they are. Clearly, we have one in the front, but there's also one here, there's one here, there's one here, there's one here, there's one here, there's one here. In fact, you could basically spend the whole day identifying the hundreds of urine-diverting toilets that dot this community. In this particular community, the urine is collected in storage containers and then collected by trucks for recycling. The dried feces that come out of the storage chambers here are simply buried on site. This is one of the technology combinations that is possible on the system template that we just went through. So in summary, waterless technologies, or technologies like pour flush toilets that do not require a lot of water are not necessarily simple, and the systems built around waterless technologies can in fact become very complicated. System building is left to right, but may require iteration, especially when the needs and uses of the products that remain at the end of the system are taken into account. In the next module, we'll take a look at decentralized water based systems. I hope you'll join me then.
