This project arose from difficulties with water management at two burns. At Burning Man, you need to do something with all of the grey water you produce: evaporate it, pay for pumping, or haul it out. Showers are by far, one of the larger generators of grey water. Historically our camp attempted an evaporation pond, but in the end it just concentrated the contaminated water and made a mess no one really wanted to deal with. After that we collected the grey water and payed for pumps. This was a workable solution, but I’ve always been curious if we could reclaim that water for more showers. At Critical Northwest, because we had the luxury of a robust and active biome to work with, shower runoff, with biodegradable soaps, was easily absorbed and broken down by the forest. Over the years, some camps got lax and were dumping kitchen solids or creating standing grey water pools and the event decided to ban any form of water dumping in order to protect the environment of the event. This meant that Critical faced the same grey water management issues as Burning Man. Enter, the recirculating shower.

Recirculating showers are pretty common in the RV/Trailer camping world, but they are usually focused on servicing a small group, usually a couple or at most a nuclear family, that is already pretty comfortable with each other so the systems only really need to make the water clean enough to allow for eliminating obvious signs of hygienic issues. Complaints about these systems usually focus on the slowly increasing concentration of soapiness in the recirculating shower water, which also means body oils, salts, and shed viruses and bacteria. As dirty and hippy as Burning Man attendees are, “showering in each others bath water,” as a camp mate so eloquently put it, is still a bridge too far. This recirculating shower is an attempt to use techniques that have achieved at least limited success in returning grey water to municipal drinking water standards for reclaiming grey water.

The Design

Note: several manual shutoffs are not shown on the diagram.

Clean water flows out of the system into an inline water heater and then on to the shower head. After use, the water is collected by a shower base and drawn by a pump back into the recirculating system. The pump is only engaged when flow is detected out of the system and then runs until the flow through the filtration system stops. The first step of filtering is a trio of three spindown sediment filters stepping down from 1000 micron to 50 micron filter size. These filter large particulate including hair. From there, it moves through a pair of fiber filters first filtering 5 micron particulate and finishing with a 1 micron filter. In most applications the 1 micron filter would not normally be necessary, but playa dust has a significant amount of sub 2.5 micron particulate. The 1 micron filter will remove most, but not all of this. After the particulate filters, there is a Granulated Activated Carbon/Kinetic Degradation Fluxion filter. This filter is a combination of small activated carbon granules and a copper/zinc alloy filter media. The AC granules absorb organic contaminants and the KDF media induces chemical reactions that neutralize various harmful contaminants. The final step in media based filters is AC block. This compressed block of AC powder removes finer organic contaminants. The final filtration stage is a germicidal ultraviolet light filter. This final stage ensures that any viruses and small bacteria that remain in the water are destroyed. Water then flows the holding tank where an outflow pump pressurizes water for a variety of uses beyond the standard showering, described below.

The filters are oversized compared to the anticipated 1-2 week usage. Future improvements may include backflow flushing of the sediment, GAC+KDF, and AC Block filters for longer filter life.

Idle Sterilization

The environment of the recirculating system itself is not sterile and the KDF filter will neutralize chlorine. In order to ensure that the non-chlorinated water in the holding tank does not become a breeding ground for microorganisms, the system will detect idle periods and will flow water from the holding tank back through the UV-C filter. This will sterilize the entire tank periodically, ensuring that the water is microorganism free.

Spindown Filter Flush

The spindown filters include a flush valve on the pre-filter side. Due to the mechanical design of the filter, if this flush filter is opened, any particular caught by the filter will be expelled. These filters are expected to need multiple flushes during the week.

Water Dump

The playa includes sub micron particulate and viruses and many bacterial are smaller than will be filtered. This means that over time the turbidity of the water will increase to the point that the UV-C filter is no longer effective at sterilizing the water. This typically occurs long before people will notice and be put off by the cloudiness. The holding tank includes a turbidity sensor that will alert operators that the water needs to be dumped if it exceeds a pre-programmed threshold. Additionally, at the end of the event, the system must be flushed and filled with sanitizer for storage.

The Build

The plumbing is all assembled, but the electronics still need work. Next steps are

  1. Fill the system and manually test each flow mode

  2. Complete electronics build

  3. Test completed system at home

  4. Test system at Critical

  5. Test system at Burning Man






System Characterization & Future Work

During the tests at Critical and Burning Man, I will be taking samples from the holding tank through the week. These samples will be sent for lab analysis to determine actual water quality. The analysis will determine if the system meets the needs or if it needs to be reworked. If it works well enough for showering, we may tie dishwater and handwashing stations into the system. If the water truly meets municipal water quality standards over the course of multiple events, we may evaluate potability of the produced water.