Table 4.
Characteristics of the treated water and removal efficiencies in six on-site wastewater reuse systems compared to the results presented in this study. Rogers et al. (2018) and Sahondo et al. (2020) tested different configurations (recycling in laboratory testing, sewer discharge in field testing) of the same blackwater treatment system.
| Authors/Prototype | This study: P1 | This study: P2 | This study: P3 | Cid et al. (2018) | Rogers et al. (2018) | Abegglen et al. (2008) | Fountoulakis et al. (2016) | Santasmasas et al. (2013) | Sahondo et al. (2020) | Ratanatamskul et al. (2014) |
|---|---|---|---|---|---|---|---|---|---|---|
| Recycling or downcycling | Recycling | Recycling | Recycling | Recycling | Recycling | Downcycling >65% | Downcycling | Downcycling | Once-through | Once-through |
| Water treated | Greywater | Greywater | Blackwatera | Blackwater | Blackwatera | Blackwater | Greywater | Greywater | Blackwatera | Blackwater |
| Reuse purpose | Hand washing | Hand washing | Flushing | Flushing | Flushing | Flushing + irrigation | Flushing | Flushing | Flushing | Flushing + irrigation |
| Energy | 6.9 Wh/L | 0.5 Wh/L | 0.4 Wh/L | 35 Wh/L | 5.6 Wh/L (disinfection only) | n.a. | 4.2 Wh/L | 2.9 Wh/L | 15.2 Wh/L | n.a. |
| Testing context | Public park, Switzerland | Public street, South Africa | Single household, South Africa | Elementary school, China | Laboratory-testing | Single household, Switzerland | Single household, Greece | Office building, Spain | Ablution block, South Africa | University building, Thailand |
| Duration (days) | 63 | 74 | 94 | 30 | 40-120 UDEb | 100 | 400 | 250 | 92 | 105 |
| Chemical composition of the treated water: mean (min-max) | ||||||||||
| COD (mgO2/L) | 5.5 (2.5–11.5)d | 9.1 (<3–36) 99.7% removal |
7.5 (<3–44) 99.8% removal |
170 (100–300) 70% removalc |
945 (579–983) | 38.1 93% removal |
59 (34–157) 87% removal |
29 (5–74) 90% removal |
61 ± 49 85% removal |
<10 >90% removal |
| Total nitrogen (mgN/L) | 9.1 (7.4–12.1) 98.5% removal |
33.2 (19–44) 95.7% removal |
20 (8–47) 40% removal |
22 (14–30) 4% removal |
102 ± 20 45% removal |
|||||
| NH4 (mgN/L) | 0.07 (<0.015–1.2) | 0.16 (<0.02–1.3) | 0.93 (<0.02–7.8) | 150 (60–375) 70% removalc |
1.04 99% removal |
1 >90% removal |
||||
| NO3 (mgN/L) | 6.5 (2–9.9) | 5.5 (10–13) | 24.6 (10–35) | 45 | 0.2 | 25 | ||||
| Total phosphorus (mgP/L) | 16 (8.6–26.2)e | 4.4 (2.1–11.0) 99.9% removale |
25.4 (10.6–33.4) 89.6% removale |
17 29% removal |
0.4 (0.1–1.6) 69% removal |
3 (2–8) | 14 ± 12 20% removal |
0.3 | ||
| pH (−) | 7.3 (6.7–7.7) | 8.0 (7.1–8.4) | 7.3 (6.7–7.8) | 7.9 (7.0–8.6) | 7.9 (7.5–8.3) | 7.0 ± 0.6 | 7.5–8.3 | |||
| EC (us/cm) | 2490 (2060–2870) | 1480 (720–1900) | 15,000 (14,000-16,400) | 38.1 93% removal |
800 (600–1900) | 1240 (930–1630) | ||||
| Pathogen indicators in the treated water: mean (min-max) | ||||||||||
| E. coli (MPN/100 mL) | <1 | <1 | <1 (<1–3.1) | <1 | <1 | <5 (<5–100, CFU/100 mL) | <1 | <1 | ||
| Tot. Coliforms (MPN/100 mL) | <1 (<1–2) | <1 (<1–56.5) | 9 (max. after 4 h disinf.) | 1.3 (<1–18) | <1 | |||||
| Appearance of the treated water: mean (min-max) | ||||||||||
| Color (Pt/Co) | 0 | 0 | 86 (25–150) | 90 max | ||||||
| Turbidity (NTU) | 0.4 (0.1–1) | 0.4 (0.1–0.8) | 155 (106–192) | 5.0 (1.5–9.9) | 3 ± 1 97% removal |
0–0.1 | ||||
| TSS (mg/L) | 0.4 | 1.7 | 138 (52–216) | 8 (4–12) | 1.3 (<1–5) | 23 ± 13 65% removal |
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a
Blackwater separated from the major part of urine and solids (this study) or solids (Sahondo et al., 2020; Rogers et al., 2018).
b
UDE: user-day equivalent.
c
Concentrations: estimated from Fig. 7 in Cid et al. (2018). Removal: comparison between input and output concentrations; not all data available to calculate overall removal for the complete field trial duration.
d
Assumed COD/DOC = 2.5 gO2/gC.
e
Phosphate.