This document discusses the reuse of greywater in buildings. It provides an overview of greywater quality guidelines, treatment technologies, and case studies of greywater reuse systems. Some key points include: - Greywater accounts for 50-80% of household wastewater and can be treated and reused for purposes like toilet flushing and irrigation. - Treatment typically involves physical separation followed by disinfection. Promising technologies include membrane bioreactors and constructed wetlands. - Case studies from Norway, Italy, Germany demonstrate greywater systems that consistently achieve high removal of contaminants to meet reuse standards.

1. METROPOLITANA
MILANESE SPA
The reuse of grey water in buildings
Sabino DE GISI, Patrizia CASELLA, Roberto FARINA

2. Framework
• Introduction
• Towards a Resource Oriented Sanitation Approach
• Objective of the study
• Gray water (GW) quality
• Guidelines for Grey Water reuse
• Technologies for Grey Water treatment and reuse
• Case studies
• Case 1: klosterenga, Oslo, Norway
• Case 2: Preganziol, Treviso, Italy
• Case 3: Bologna, Italy
• Case 4: Berlin-Kreuzberg, Germany
• Where the reuse is essential (Some remarks of the Zero
Project)
• Conclusions
• References

3. Introduction
Open issues
• Generally, segregation of domestic sewage into black water
and grey water components should be regarded as a
significant outcome of new conceptual developments
concerning waste as a resource;
• This involves a change in the conventional end of pipe
approach currently used to the present day;
• An open challenge in the water & wastewater sector, refers to
the upgrading of the sewerage system of cities with a great
investments for governments all over the world;
• In some cases, the adoption of a «Resource Oriented
Sanitation Approach» may be the most suitable solution in
terms of technical, environmental and economic aspects.

4. Resource Oriented Sanitation
• It’s the case of the Hamburg Water Cycle
(HWC), an innovative and integrated concept
for wastewater treatment and energy
generation;
• The HWC has been developed by
Hamburg’s water supply and wastewater
utility Hamburg Wasser, with around 610
connected households for about 2000
inhabitants;
• It is the largest demonstration of the
resource-oriented sanitation in Europe.
Open issues

5. CITY OF
HAMBURG

6. CITY OF
HAMBURG

7. Resource Oriented Sanitation
Integrated approach for Water & Energy
• The concentrated blackwater and additional biomass will utilized for biogas
production in a district anaerobic digester;
• Biogas will be used for the generation of carbon neutral heat and electricity in
a combined heat and power plant;
• Grey water, from showers, sinks, etc., will be treated in decentralized system;
• Local rain water management closes the natural water cycle.

8. The objective
In this context, the aim of work is to describe the state
of the art of:
• Grey water characteristics;
• Guidelines for grey water reuse.
Identifying, subsequently, the:
• Appropriate technology solutions.
These goals are pursued by means of several case
studies.

9. Grey water quality
1
Types of grey water and production [L/person/day]
• With reference to a residential home, we have the following fluxes:
Bathroom Laundry Kitchen Dishwasher
Mixed
• With reference to the production, the typical volume
of grey water varies from 90 to 120 L/person/day.
• While, for low income countries with water shortage,
the production is about 20 – 30 L/person/day.

10. Grey water quality
Organic matter & total suspended solids
100
200
300
400
500
600
700
800
900
1000
1100
1200
1300
1400
1500
1600
1700
1800
1900
2000
2100
2200
2300
2400
2500
2600
2700
2800
2900
3000
0
COD
BOD5
Bathroom Laundry Kitchen Dishwasher
TSS
Mixed grey water
Parameter
Concentration
[mg/L]
Kitchen grey water and laundry
grey water are higter in both
organics and TSS!
1

11. Grey water quality
0.0
2.5
5.0
7.5
10.0
12.5
15.0
17.5
20.0
22.5
25.0
27.5
30.0
32.5
35.0
37.5
40.0
42.5
45.0
47.5
50.0
52.5
55.0
57.5
60.0
62.5
65.0
67.5
70.0
72.5
75.0
TN
TP
Parameter
Concentration
[mg/L]
Nutrients (NTOT & PTOT)
Bathroom Laundry Kitchen Dishwasher Mixed grey water
171
1

12. Grey water quality
C:N:P ratio and biodegradability
• All type of grey waters show good biodegradability in terms of COD:BOD5
ratio;
• Compared to the suggested COD:N:P ratio of 100:20:1, bathroom grey
water, laundry and mixed ones are deficient in nitrogen.
Bacterial load & pH
1

13. Guideline for GW reuse
Wastewater reuse standard
• Today, very few reuse guidelines are particularly made for grey water
recycling.
2
Guideline
Types of reuse
Toilet flushing Irrigation Washing
A: Germany (1999)
B: China (2006)
C: USA (2007)
D: Japan (1996)
E: Australia (2003) Regardless of the type of use

14. Guideline for GW reuse 2
Wastewater reuse standards: Values

15. Technologies
Technologies
for grey water treatment and reuse
• Technologies for grey water treatments include physical, chemical
and biological systems.
• As reported in Li et al. (2009), most of these technologies are
preceded by a solid-liquid separation step as a pre-treatment and
followed by a disinfection step as post treatment.
• To avoid the clogging of the subsequent treatment, the pre-treatments
such as septic tank, filter bags, screen and filters are applied to
reduce the amount of particles and oil and grease.
• While, the disinfection step is used to meet the microbiological
requirements.
3
Pre-treatment Grey water Technology Disinfection To reuse
Oil and grease Particles
Disinfectant

16. Technologies
3
Technologies
for grey water treatment and reuse
Physical processes
Technologies
Cartridge filter
Chemical processes Biological processes
Filtration
Screening +
Sedimentation +
disinfection
Membranes (UF,
NF, RO)
Filtration +
Activated Carbon
+ Sand filter +
Disinfection
Electro-coagulation
+
Disinfection
Coagulation +
Sand filtration +
GAC
Coagulation with
aluminium salt
Magnetic ion
exchange resin
Sedimentation + RBC +
UV Disinfection
Screen + RBC + Sand
filtration + Chlorination
Membrane Biological
Reactor (MBR)
UASB (upflow anaerobic
sludge blanket reactor)
Constructed
wetlands
Sequencing
Biological Reactor
(SBR)

17. Technologies 3
Technologies for grey water treatment and
reuse
Average Mixed
Grey water
Parameter
Guideline/Percentage removal
BOD
COD
TN
TP
TSS
Torbidity
T. Coliform
F. Coliform
pH
<Value>
256.5
400.0
18.0
11.5
104.0
202.0
4.0∙107
7.5∙107
7.2
A
5
<100/ml
< 10/ml
(for Toilet flushing)
% Removal B
98.1%
99.9%
99.9%
10
10 44.4%
< 3/100 ml
% Removal
96.1%
97.5%
99.9%
5
6 - 9
C % Removal
10
2 99.0%
< ND/100 ml
96.1%
100.0%
Guidelines: A = Nolde (1999), Germany; B = Ernst et al. (2006), China; C = Asano (2007), USA

18. Technologies 3
Technologies for grey water treatment and
reuse
Mixed Average Grey water
Guideline
A
B
C
(for Toilet flushing)
BOD TN Torbidity T. Coliform Considerations
(98.1%)
F. Coliform
(99.9%) (99.9%)
Need to remove BOD > 98% and
bacterial load (> 99%)
(96.1%) (44.4%) (97.5%) (99.9%)
Need to remove BOD > 96%, TN > 44%,
Torbidity > 97% and F. coliform (> 99%)
(96.1%) (99.0%) (100%)
Need to remove BOD > 96%, Torbidity >
99% and F. coliform (> 99%)
Guidelines: A = Nolde (1999), Germany; B = Ernst et al. (2006), China; C = Asano (2007), USA
(for Toilet flushing)
Organic Matter Nitrogen Torbidity Bacterial load
High Moderate High High
Degree of removal (High; Moderate; Low)
We need to remove Torbidity (>90%), Organic
matter (>95%), Nitrogen (> 40%)and
microbiological parameters (>99.9%)

19. Technologies 3
Which processes allow to obtain these
removals?
Processes
Cartridge filter
Screening + Sed. + Disinfection
BOD TN Torbidity T. Coliform F. Coliform Is it good?
- - (99.0%)
-
(54.4%) (37.3%) (15.0%) -
-
(55.9%) -
(48.6%) - -
(66.7%)
NF membrane
RO membrane
Filtration + Activated Carbon +
Sand filtration + Disinfection
(93.4%) - (96.7%)
- -
(97.7%) - (100%) -
-
(31.4%) -
(53.8%) - -
UF membrane
(94.9%) - (85.7%) - -
Sed. + RBC + UV disinfection
Screen + RBC + Sand filt + Chlor.
MBR
(98.0%) (90.0%) (90.0%)
(99.0%) (99.0%)
(96.1%) - (98.2%) -
(100%)
(98.8%) -
(99.5%) - (100%)
Coagulation + Sand filtration +
GAC
SBR (87.9%) (11.4%) - - -
Target: BOD > 90%; TN > 40%; Torbidity > 90%; Microbial parameters > 99.0%

20. Technologies 3
Technologies for grey water treatment and
reuse
• The combination of aerobic biological processes with
physical filtration and/or disinfection is considered to be the
most economical and feasible solution.
• Instead, biological treatment as the RBC (Rotating Biological
Contactor) system will become economically feasible when
the building size reach a certain dimension.
• The MBR (Membrane Bio Reactor) is the only technology being
able to achieve satisfactory removal efficiencies of organic
substances, surfactants and microbial contaminations
without a post filtration and disinfection step.

21. Klosterenga, Oslo
Bologna
Berlin-kreuzberg
Preganziol, Treviso
Case studies

22. Case study (1)
Klosterenga, Oslo, Norway

23. Case study (1)
Klosterenga, Oslo, Norway
• Klosterenga, a 35-unit residential
apartment building, an example of
integrated design considering
energy and water nexus.
• Each apartment has a dual waste-pipe
system where toilet waste is
pumped directly to the municipal
sewage system.
• While grey water is pumped to
the filtration system in the
courtyard.
• In addition, rainwater is captured
in rain barrels and used in the
garden.
Additional funding for the
realization of the project

24. Case study (1)
Klosterenga, Oslo, Norway
• During its operation, since 2000, the Klosterenga system has consistently produced
an effluent with the following average parameters (Jenssen, 2004):
• COD = 19 mg/l; Total nitrogen = 2.5 mg/l; Total phosphorus = 0.03 mg/l; Faecal
coliforms = 0.
• For nitrogen the effluent has consistently been below the WHO drinking water
requirement (UNEP, 2006) of 10 mg/l and for bacteria no faecal coliforms have been
detected.

25. Case study (2)
Preganziol, Treviso, Italy

26. Case study (2)
Preganziol, Treviso, Italy
• The system was designed for 240 populations equivalent (PE) in which grey water is
treated with two constructed wetland systems (horizontal subsurface flow - HSF).
• The two reed bed are completely waterproofed, filled with fine gravel and planted with
phragmites australis.
• Treated grey water, collected in a cistern, is subsequently used for toilet flushing by
means of an indoor distribution system.
• Instead, rainwater is at first treated in a vertical flow constructed wetland system (with
a surface of 50 m2) and then collected in storage tanks. Subsequently, rainwater and/or grey
water are used for irrigation.

27. Case study (3)
Bologna, Italy

28. Case study (3)
Bologna, Italy
Distribution of consumptions
Treatment scheme
Water saving

29. Case study (4)
Berlin-Kreuzberg, Germany

30. Case study (4)
Berlin-Kreuzberg, Germany
• Apartment house for 70
persons;
• The grey water treatment
scheme includes
sedimentation, biological
system with RBCs, final
sedimentation and UV
disinfection.

31. Where the reuse is essential...
MENA countries and Turkey
http://www.zer0-m.org/

32. Where the reuse is essential...
MENA countries and Turkey http://www.zer0-m.org/
SBR
Training and demonstration
centre (TDS) general layout
in Turkey
RBC
MBR

33. Conclusions
With reference to the grey water characteristics, the
following main conclusions can be withdrawn:
• All types of grey water have good biodegradability;
• The bathroom and the laundry grey water are deficient in both nitrogen
and phosphors;
• The kitchen grey water has a balanced COD:N:P ratio.
Considering technologies:
• Physical processes alone are not sufficient to guarantee an adequate
reduction of the organics, nutrients and surfactants;
• Chemical processes can efficiently remove the suspended solids, organic
materials and surfactants in the low strength grey water;
• The combination of aerobic process with physical filtration and disinfection
is considered to be the most economical and feasible solution for grey
water recycling;
• The MBR (Membrane Biological Reactors) appears to be a very attractive
solution in collective urban residential buildings.

34. Conclusions
In addition:
• The main advantage of the water recycling is in the saving of the water
resource while, the main disadvantage is in the realization costs.
• However, an integrated design of the building (considering water and
energy nexus) could make it more economically sustainable.

35. References
• Amr M. Abdel-Kader (2013) Studying the efficiency of grey water treatment by using rotating biological contactors system.
Journal of King Saud University – Engineering Sciences. 25, 89-95.
• Ernst, M., Sperlich, A., Zheng, X., Gan, Y., Hu, J., Zhao, X., Wang, J. and Jekel, M. (2008) An integrated wastewater
treatment and reuse concept for the Olympic Park 2008, Beijing. Desalination 202(1-3), 221-234.
• Failla, B. and Stante, L. (2006). Efficient Management of Wastewater Treatment and Reuse in the Mediterranean
Countries. Experimental Aquasave Project in households, Technologies and Results. In the proceedings of the Regional
EMWater Project Conference, from 30 October to 1 November, Amman, Jordan.
• Friedler, E., Gilboa, Y. (2010) Performance of UV disinfection and the microbial quality of greywater effluent along a reuse
system for toilet flushing. Sci. Total. Environ. 408, 2109-2117.
• Jefferson, B., Judd, S. and Diaper, C. (2001) Treatment methods for grey water. In “Decentralised Sanitation and Reuse,
Concepts, systems and implementation”, edited by P. Lens, Zeeman G and Lettinga G., IWA Publishing, ISBN: 1900222477.
• Jenssen, P.D. (2004). Decentralized urban greywater treatment at Klosterenga Oslo. In: H.v. Bohemen (Ed.) Ecological
engineering-Bridging between ecology and civil engineering, Æneas Technical Publishers, The Netherlands, pp 84-86.
• Li, F., Wichmann, K. and Otterpohl, R. (2009) Review of the technological approaches for grey water treatment and
reuses. Sci. Total. Environ. 407(11), 3439-3449.
• Maeda, M., Nakada, K., Kawamoto, K. and Ikeda, M. (1996) Area-wide use of reclaimed water in Tokyo, Japan. Water
Sci. Technol. 33(10-11), 51-57.
• Masi, F., El Hamouri, B., Abdel Shafi, H., Baban, A., Ghrabi, A. and Regelsberger, M. (2010) Treatment of segregated
black/grey domestic wastewater using constructed wetlands in the Mediterranean basin: the zer0-m experience. Water Sci.
Technol., 61(1), 97–105.
• Morel, A., Diener, S. (2006) Grey water management in low and middle-income countries. Water and Sanitation in
Developing Countries (Sandec). EAWAG.
• Nolde, E. (2000) Greywater reuse systems for toilet flushing in multi-storey buildings – over ten years experience in Berlin.
Urban Water 1, 275-284.
• Oron, G., Adel, M., Agmon, V., Friedler, E., Halperin, R., Leshem, E. and Weinberg, D. (2014). Greywater use in
Israel and worldwide: Standards and prospects. Water Res., 58, 92-101.
• UNEP, 2006. WHO Guidelines for the safe use of wastewater, excreta and Greywater. In: Policy and Regulation Aspects, vol.
1. WHO, 20 Avenue Appie, 1211 Geneva 27, Switzerland p-100.

36. Sabino DE GISI, PhD
sabino.degisi@enea.it
Patrizia CASELLA, PhD
patrizia.casella@enea.it
Roberto FARINA, MSc
roberto.farina@enea.it
METROPOLITANA
MILANESE SPA
Italian National Agency for the New Technology, Energy and Sustainable
Economic Development, Water Resource Management Lab.
Via Martiri di Monte Sole 4, 40129, Bologna (ITALY)