Resource Recovery Based Sanitation: integrating collection and transport with treatment and re-use

“Resource recovery and in particular phosphorus recovery, will become an unavoidable necessity within several decades (Cordell et al, 2009). As there is no replacement for phosphorus in the growing of crops, this natural resources will become scarce within a foreseeable period. Though there is not a clear view on how long that period will be, it will be in the same order of magnitude as the lifetime of a complete sanitation system in present urban and metropolitan environments. Historically the present systems were developed over the last 150 years, starting around 1850 in London and steadily growing, leading to very high connections rates nowadays in Western type cities. The present system is based on hydraulic transport of water and solids and aimed at hygiene, safety and comfort. The majority of the present system is a classic combined system dealing with both storm water and sanitary waste water.
In the last couple of decades the importance of treating water before discharging it in the environment became imminent, which led to a literally ‘end-of-pipe’ treatment. The treatment can be characterised as ‘effluent-oriented’, namely to produce an effluent quality that can safely be discharged to the environment. The treatment puts extra demands to the collection and transport system with respect to the total volume collected and offered to the process. Treatment costs are eventually related to this volume and make the separate collection of storm water and sanitary waste water also an economic question.
The need for resource recovery adds, again, a new variable to the design and operation of the sewer system. Treatment is now targeted at recovering substances from the waste water in such a way that it can be re-used. Resource recovery as a new variable is an addition: the other requirement of hygiene, safety, comfort, environmental discharge still are valid and even becoming more stringent. Considering all design parameters it is evident that they may pose conflicting requirement to the collection and transport system. Local hygiene, safety and comfort may be satisfied with a single pipe for all urban water, discharging at a local water body. Regional hygiene, safety and comfort require treatment before discharge and benefit from restricted volume flows offered to treatment. Resource recovery require intensive treatment and is served best with a small, but concentrated flow to be treated.
“During the reconstruction the service will continue” sounds like a generous offer, but is in fact a necessity. In the transition from local to regional an element of transport and central treatment was introduced, which made it relatively easy to continue the service. The transition from regional treatment to resource recovery will be done in the coming decades. This paper explores possibilities for a new system choice.”

(Citation: Vreeburg, J.H.G. – Resource Recovery Based Sanitation: integrating collection and transport with treatment and re-use – CCWI Conference, Amsterdam, 7-9 November 2016)