Reusable water from fecal sludge in an instant!

4 Poster Track: Applied Research » 4 Innovative technology aspects

Speaker: Andrew Groves

Summary – for publication in conference brochure:

The Oystra® system is a compact, scalable, high capacity treatment technology for numerous fecal sludge treatment applications. The unique filtering system converts 50–75% of the incoming septage to clean safe reusable water.  The filtering system can also concentrate 50-60% of the nutrients into a pathogen free stream for reuse.  Oystra® has processed nearly 1,900m3 of septage in two regions of the USA and is planned to ship to Dakar, Senegal for joint septage testing with DELVIC Sanitation Initiatives S.A. in early 2021.

Introduction, methods, results and discussion:

The Oystra® prototype is compact enough to fit on a truck and maneuver through informal settlements processing approximately 180 liters/minute of septage (Figure 1).  The system requires no startup time and can process septage immediately upon arrival on-site.  The system controls are simplistic and fully automatic and after processing, automatically flushes with water produced during processing.

Oystra® contains three filtering systems, each with unique functions.  The first filter removes large debris like rocks and wood commonly found in pit latrines.  The second filter is a membrane-based filter removing suspended solids and pathogens.  The third filter is also a membrane-based filter removing dissolved pollutants. 

The current design has four outputs: (1) trash & debris, (2) concentrated solids, (3) dissolved organics and nutrients, and (4) clean water. The first two streams contain pathogens and require further treatment at a waste treatment plant. The third stream meets pathogen removal requirements and includes the highest concentration of valuable nutrients – nitrogen as ammonia, phosphorus, and potassium. This stream can be bundled with the first two streams for further treatment or utilized for fertilizer. 


Figure 1 Mobile version of Oystra®

The full-scale prototype has been tested in the USA processing septage in Wisconsin and Washington State (0.1-4.6 %TS, 334-32,000 mg COD/L).  The processor is being prepared to test at the Tivaoune Peulh-niague Fecal Sludge Treatment plant in Dakar, Senegal to demonstrate its applicability in the target market.

Approximately 50-75% of the septage input volume is returned as clean safe water for reuse or local discharge.  This water is of exceptional quality making it highly suitable for agriculture or industrial reuse opportunities.

Effluent water quality results have demonstrated Total Solids % averaging less than 0.02% with the average COD less than 40mg/L and no detectable E. coli in the majority of samples (N=116).  Effluent water has no visible color or other defects (Figure 2). Average effluent water concentrations meet the standards published in ISO 30500 and aim to meet forthcoming ISO 31800 standards.


Figure 2 Input septage sample and effluent water sample – Washington State trials


The operating scenarios where Oystra® may be deployed in the sanitation circular economy are numerous.  The focused business scenario is to travel pit-to-pit concentrating the fecal sludge volume that pit emptiers transport to treatment plants which are often located far from informal settlements.  The reduced volume lowers the pit emptiers’ cost by lowering the number of trips to the treatment plant for the same number of pits emptied.  Similarly, Oystra® could be used in a transfer station model where septage is brought to the edge of the settlement for treatment. 

Stationary applications include apartment or community toilet block complexes where water reuse treatment is needed onsite.  Oystra® can also be utilized in a fecal sludge treatment plant connected to an Omni-Processor or to increase the capacity of over utilized treatment plants that do not have land to expand.  The technology is easily scaled in size depending on the application, making each of these scenarios feasible.  

Conclusions and implications:

The Oystra® processing results have proven consistent effluent quality and the capability to generate a significant volume of reusable water, from a very difficult to process raw material, which is valuable in a water stressed environment.  Validation of the USA results in Dakar will further prove viability in target markets so the technology can be applied to numerous applications from fecal sludge treatment plants to small scale building complex systems where high-quality water is of value.  Part of the testing in Dakar will be Oystra® economic validation for various applications with the support of DELVIC, who will be instrumental in the study.

Potential commercial partners are welcome to visit during the technical and economic validation of Oystra® in Dakar by contacting Crane Engineering or DELVIC.

Relevant references:

Sun Kim
Program Director Bill & Melinda Gates Foundation

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