Prospects of Source-Separation-Based Sanitation Concepts: A Model-Based Study

Abstract

Separation of different domestic wastewater streams and targeted on-site treatment for resource recovery has been recognized as one of the most promising sanitation concepts to re-establish the balance in carbon, nutrient and water cycles. In this study a model was developed based on literature data to compare energy and water balance, nutrient recovery, chemical use, effluent quality and land area requirement in four different sanitation concepts: (1) centralized; (2) centralized with source-separation of urine; (3) source-separation of black water, kitchen refuse and grey water; and (4) source-separation of urine, feces, kitchen refuse and grey water.The highest primary energy consumption of 914 MJ/capita(cap)/year was attained within the centralized sanitation concept, and the lowest primary energy consumption of 437 MJ/cap/year was attained within source-separation of urine, feces, kitchen refuse and grey water. Grey water bio-flocculation and subsequent grey water sludge co-digestion decreased the primary energy consumption, but was not energetically favorable to couple with grey water effluent reuse. Source-separation of urine improved the energy balance, nutrient recovery and effluent quality, but required larger land area and higher chemical use in the centralized concept.

Integrated, Decentralized Wastewater Management for Resource Recovery in Rural and Peri-Urban Areas

“…The environmental impact contribution of the sewer system, often erroneously assumed as negligible, has been shown to be more relevant than that of WWTPs on a large part of analyzed projects. Tervahauta et al [23] calculated primary energy consumptions of standardized, centralized, and decentralized collection systems based on Dutch conditions; their findings show that the highest primary energy consumption of 914 MJ/cap/year occurs within centralized sanitation cases. By introducing source-separation of urine, direct energy consumption can decrease to 687 MJ/cap/year.…”

“…Separation of different domestic wastewater streams, aimed at differentiated on/off-site processing for resource recovery/recycling, is now recognized as one of the most promising concepts to re-establish sustainable management in carbon, nutrient, energy, and water cycles [23,54], although there is still ample resistance to the generalized adoption of this paradigm. It is well known that domestic wastewater can be divided into two major streams: concentrated blackwater (feces and urine, sometimes mixed with kitchen refuse), and less concentrated greywater from various washing activities.…”

“…They may be very well accepted when their objectives and advantages (including economical ones) have been clearly illustrated to users, as frequently happens with other environment-related projects [22]. In a few EU countries (Germany, The Netherlands) demonstrative decentralized systems serving up to 1000 people have been implemented in urban areas (examples: Knittlingen and Jenfelder Au, Sneek), incorporating reuse of water, energy, and resources, and receiving vast support by residents [23,24].…”

Improved Energy Recovery by Anaerobic Grey Water Sludge Treatment with Black Water

“…This increase is lower compared to the theoretical one calculated in the study of [14] (73%) and could be due to the MBR used to bioflocculate grey water, producing a higher loading of grey water sludge of 40 compared to 29 gCOD/cap/d in this study. In the study of Tervahauta et al [23], however, the calculated increase in the energy recovery of 28% is similar to this study using an A-trap to bioflocculate grey water. The increased energy recovery in the MIX-UASB reactor is equivalent to 55 MJ/cap/y primary energy and can cover the increased heat demand of the MIX-UASB reactor of 27 MJ/cap/y with a surplus of 28 MJ/cap/y.…”

“…The increased heat demand of the MIX-UASB reactor was due to the heating of the additional influent stream of grey water sludge and the increased heat loss through the reactor walls of the larger reactor. The heat demand was calculated according to Tervahauta et al [23] by using grey water sludge production of 1.0 L/cap/d and a temperature of 19…”