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Semi-centralized water systems for rapidly growing urban areas
Martin Wagner*, Peter Cornel* *Technische Universitaet Darmstadt, Institut WAR, Petersenstr. 13, 64287 Darmstadt, Germany
Abstract: The rapid development of big cities worldwide leads to infrastructure problems regarding water supply and sanitation systems. Conventional systems cannot keep up with the rapid growth of the cities. In recent years there have been many discussions about alternative supply and sanitation systems, which are to solve the discrepancy between city growth and the demand for supply and sanitation systems. Furthermore, these systems should deal in a sustainable way with natural resources. Different kinds of sanitation systems are discussed, as alternatives for conventional central sanitation systems, so-called “End of Pipe” systems. The existing experience about conventional supply and sanitation systems must be evaluated and new systems must be adapted to the local boundary conditions of future cities. The paper presents a supply and sanitation system (semi-centralized sanitation system) which might prove as a solution for rapidly growing big and also mega cities.
Keywords: rapid city development, big cities, sanitation systems, semi-centralized sanitation systems
IntroductionIn the future, modern city planning should put a higher emphasis on the principle of sustainable development than it has done until today. Furthermore, city plan-ning should deal conscientiously with the environment in order to get a higher acceptance on the part of the cities' inhabitants. Infrastructure planning is one of the most important sectors of city planning. Therefore, infrastructure planning should follow the development of the cities (spatial spread) to guarantee effi-cient supply and disposal services. However, there are multifaceted problems especially in rapidly growing cities, and infrastructure cannot fulfil its duties and responsibilities. Thus, the supply of the city with drinking water, the treatment of waste water and the disposal of waste cannot be ensured.
In this paper, after some facts about future city development are listed, sanitation systems will be introduced in detail. Then so-called semi-centralized sanitation systems and semi-centralized supply and treatment systems are described and compared with conventional centralized and decentralized sanitation systems. Finally, a conclusion rounds off the paper.
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2 Semi-centralized water systems for rapidly growing urban areas
Future city developmentThere are several main reasons which might influence the development of big cities worldwide. Three of them will be discussed below:
The development of cities is different all over the world. In 1994, only three of the world's 10 largest cities were located in developed coun-tries. By 2015, this number is expected to decline further to two, one will be Tokyo (Japan). However, whereas Tokyo’s population is esti-mated to increase by less than 5 percent during this period, cities like Jakarta (Indonesia), Karachi (India), Lagos (Nigeria), and Dhaka (Bangladesh) are expected to grow 60 to 75 % [Biswas et al., 2004]. In 2015, from the estimated 27 mega cities - cities exceeding a population of ten million inhabitants - there will be 15 in Asia [cp. Dhakal, 2002].
There is a difference between the growth of big cities in the developed and the developing world. For example, New York, Paris and London are three mega cities in the developed world. These cities have grown continuously throughout the 20th century. The growth tendency of mega cities nowadays has changed. The development in a gradual process over a long period, such as New York and London, allowed progressive and effective development of the necessary infrastructure systems, e.g. sanitation systems [cp. Biswas et al. 2004]. In contrast, the develop-ment of big or mega cities in developing countries is much faster. Therefore, necessary infrastructure development cannot keep up with the rapid growth of these cities.
Beside the rapid growth of big cities urbanization is increasing, too. In 2000, more than half of the world’s population lived in cities. During the past 30 years, the urban population in developing countries has tri-pled. Urban areas in Africa, Asia and Latin America are growing with an average rate of one million people per week [Perlman et al., 1998]. Africa has the fastest rate of urban growth in the world. It is expected that by 2025 the continent’s urban population will have grown from 300 million to 700 million or from 30 % to 52 % of the total population [Cross and Morel, 2004]. Developing countries will absorb nearly all of the world’s population increase between today and 2030. The estimated urban growth rate of 1.8 % per year for the period between 2000 and 2030 will double the number of city dwellers. Meanwhile, rural popula-tions are growing hardly at all. Likewise by 2030 more than half of all Asians and Africans will live in urban areas. In Latin America and the Caribbean, at the same time, 84 % of the inhabitants will live in urban areas, a level comparable to the United States [Abhat et al., 2005]. Ur-banization in developing countries is increasing, even with declining industrialization and infrastructure and despite fewer jobs and decreas-ing salaries. Infrastructure development cannot keep up with the rising number of city dwellers. Therefore, the new big cities in the developing world have particular problems with insufficient infrastructure systems.
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Semi-centralized water systems for rapidly growing urban areas 3
One result of the rapid growth of big cities is lack of water. The local water de-mand of big cities is much higher than the availability of usable natural water resources, a fact almost independent from the regions' climatic conditions. The high population density of big cities leads to a great demand for water in a com-paratively small area and thus to the exploitation of water resources. Further-more, because of the rapid city development the lack of sanitation systems and waste water treatment plants leads to additional pollution of the available water resources. Thus, the usable water resources will be reduced twice: (1) by the enormous water demand due to the high population density, (2) by polluting the natural water resources via discharging untreated waste water into the water bod-ies.
Evaluating the above mentioned facts one may state, that in the future, the im-provement of infrastructure systems, especially in rapid growing big cities in the developing countries, is one of the greatest challenges for countries throughout the world. For the development of future cities sustainable and adapted solutions are needed taking into account local boundary conditions. Therefore, future city planning and in particular infrastructure planning in rapidly growing cities are a challenge for all sanitary engineers, sociologists, architects, traffic and transpor-tation engineers etc.
Sanitation systems The development of future cities and thus the infrastructure is highly dependent on the efficiency of the sanitation system.
Sanitation systems can be classified into three categories. In Tab. 1 three differ-ent categories of sanitation systems are listed, which will be discussed below.
Figure 1: Categories of sanitation systems
Category Description
Iconventional “End of Pipe” systems with a com-bined sewage system or a separate sewage system and a wastewater treatment plant (WWTP)
II
separate collection of yellow water (urine) and black water (all other water). This system realizes a closed nitrogen and possibly phosphorus cycle without water reuse
III
separate collection of yellow water, grey water (from showers) and brown water (from toilet). This system realizes a closed water and nutrient cycle with water reuse
With conventional “End of Pipe” sanitation systems (category I) waste water is collected in conventional sewage systems (combined and separate sewers) and treated in a wastewater treatment plant (WWTP) – quite often located at the city's borders. In advanced treatment plants the nutrients nitrogen and phospho-
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4 Semi-centralized water systems for rapidly growing urban areas
rus are removed in order to avoid eutrophication of the receiving water bodies. The treated waste water is discharged into water bodies (river, sea, groundwater etc.). Most of these “End of Pipe” sanitation systems are so-called centralized systems. In industrialized western nations these conventional centralized system are very common.
In sanitation systems of category II, waste water from different water flows, e.g. yellow water, brown water, grey water, is collected separately. Yellow water consists of human urine and has the highest percentage of nitrogen compounds of all wastewater flows. Separately collected yellow water can be used - after a certain storage time - as fertilizer in agriculture. Brown water and grey water are not collected separately. They are pumped into a WWTP and discharged after treatment. In this kind of sanitation system water reuse is not realized but the nutrient nitrogen in the yellow water is reused in agriculture.
In sanitation systems of category III, sanitation is similar to category II regard-ing the collection and treatment of waste water; the water flows are collected separately. Water reuse in this system is realized by reusing the grey water for toilet flushing, garden irrigation etc. Grey water, which originates from showers, wash basins and washing machines, is only slightly polluted waste water, with COD levels < 400 mg/L, low in ammonia, phosphorus and faecal coliform bac-teria. No complex treatment process is needed to clean this water. After treat-ment it can be used as service water in private households or in public buildings, e.g. for toilet flushing, which is approx. 30 % of the total water demand in pri-vate households. As a result, the city's demand for drinking water is reduced significantly, thus solving part of the problems of insufficient water supply. Fur-thermore, due to water and nitrogen recycling, the cycle of water and nitrogen is partly closed. All described systems can be realized as centralized as well as decentralized systems.
Sanitation systems of category I (see Tab. 1) are normally realized as centralized systems. In centralized systems waste water from all parts of the city is col-lected, transported in a sewage system, treated in a central treatment plant and is then discharged into the receiving water bodies. Beside domestic waste water the collected waste water also contains industrial waste water. Because of the poten-tial existence of hazardous substances in industrial waste water, the reuse of this water might turn out difficult. A centralized system is designed and dimensioned for a defined period of time. Therefore, the necessary capacity of the sewage systems and treatment plants must be estimated and calculated prior to the plan-ning stage.
Sanitation systems of category II and III (see Tab. 1) can be implemented de-pending on local conditions. In totally decentralized systems, i.e. within small living communities (about 10 to 1000 inhabitants), the waste water is collected, transported, treated, discharged or reused in each individual house or a relatively small house cluster, respectively. The length of transport units (pipes, sewers) is very short; treatment units are located near the houses, and in the majority of cases the user himself operates the treatment units.
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Semi-centralized water systems for rapidly growing urban areas 5
Sanitation systems to be implemented in future cities, must be dependable, eco-nomical, and sustainable. Therefore, a flexible sanitation system with a closed cycle for water and nutrients (category III in Tab. 1) will be the preferred sys-tem, fulfilling the requirements of future sanitation systems in big cities. Beside centralized and decentralized sanitation systems there is a third system to be mentioned. In the next chapter this system – the semi-centralized sanitation sys-tem – is described as a sustainable sanitation system for rapidly growing big cities.
Semi-centralized sanitation systems as a solution forfuture cities Conventional centralized sanitation systems are developed using modern process technology, are designed to work reliably and to reach a high treatment effi-ciency, while fulfilling the economic demands at the same time. In order to transport drinking water and waste water, pipes and sewers of great lengths and large diameters are needed. The mixture of industrial and domestic waste water and the long distances between consumers and treatment plants prevent an eco-nomic water reuse [Cornel et al., 2004]. Centralized systems are not flexible enough when considering the rapid growth of the cities in the future; size adap-tation is very difficult. These cities need a very high capital investment and have to consider the estimated development prior to starting the implementation of the sanitation systems. Especially construction and enlargement measures cannot keep up with the rapid growth of the new big cities, thus resulting in higher costs compared to big cities nowadays.
The major drawback of decentralized systems is that it is difficult to guarantee constant professional operation and maintenance. The treated water for reuse purposes needs a good quality standard, and the health protection of the con-sumers must be ensured. These conditions cannot be guaranteed by the operators in a decentralized system (house owners). Furthermore, low-level technology will mostly be used in decentralized systems, thus achieving low maintenance costs and thereby low-cost systems. This may result in insufficient effluent qual-ity.
Semi-centralized supply and sanitation systems encompass the scale of applica-tion, responsibility, operation, treatment processes, and scope of reuse. Semi-centralized systems combine both the advantages of centralized and decentral-ized systems with the avoidance of their disadvantages. Compared to conven-tional centralized systems, in semi-centralized systems short pipe and sewerage systems are realized, hence the recirculation of water for reuse might be eco-nomically interesting. A separation of industrial and municipal waste water is possible, thus relieving the wastewater treatment plant as well. In relatively small areas the implementation of dual piping (for supply and reuse) is feasible, thus allowing water reuse. By using modularization, semi-centralized systems offer a higher flexibility and a better potential for enlargement and adaptation. Due to the larger scale of semi-centralized systems compared to decentralized systems, professional operation and supervision of the treatment systems are
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6 Semi-centralized water systems for rapidly growing urban areas
guaranteed. Accordingly, semi-centralized systems can keep up with the quality standards of water reuse and consumer health protection.
For future cities the semi-centralized sanitation system concept based on cate-gory III of sanitation systems (see Tab. 1) is a progressive and economic system which will offer improved water reuse in urban areas compared to today’s cen-tralized systems. With these “Semi-centralized Supply and Treatment Systems” (SESATS, see Weber et al, 2005) an efficient integrated city planning can be realized, including the necessary infrastructure measures. The relatively small service areas for SESATS allow short transport distances between the treatment units compared to centralized systems. The treatment units are situated close to each other. Therefore, the effort for integrating planning, construction and con-nection of different parts of infrastructure (water supply, wastewater treatment, solid waste disposal) can be reduced, compared to large centralized systems. When applying SESATS, well organized operating teams and systems are re-quired to guarantee the successful and safe water reuse within the city regions.
In Fig. 1 centralized and semi-centralized supply and treatment systems are compared. Centralized systems supply the whole city with tap water and also treat all of its waste water and waste. Semi-centralized systems supply single districts within a city with water and treat waste water and waste from single districts.
wastewater
emission
Citypotablewater
solid waste
energy
products
wastewater
emission
Citypotablewater
solid waste
energy
products
districtsdistricts
Figure 1: Comparison of centralized and semi-centralized supply and sani-tation systems [Weber et al., 2005]
The SESATS - as described above - combine treatment facilities for water, waste water and (organic) waste. These plants also supply service water for household use and intra-urban irrigation for one district within the city (see Fig. 2). Furthermore, because of the combined treatment of organic waste and sew-age sludge from wastewater treatment, the production of electrical energy and heat is feasible, which then can be used at the treatment plants themselves or in the neighbourhood.
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Semi-centralized water systems for rapidly growing urban areas 7
Supply and Treatment Unitwaste water
waste
pota
ble
wat
er
serv
ice
wat
er
raw water
waste treatment
wastewater treatment
water treatment
residual
waste water
ener
gy
residual
wasteSupply and Treatment Unit
waste water
waste
pota
ble
wat
er
serv
ice
wat
er
raw water
waste treatment
wastewater treatment
water treatment
waste treatment
wastewater treatment
water treatment
waste treatment
wastewater treatment
water treatment
residual
waste water
ener
gy
residual
waste
Figure 2: Scheme of one unit of a semi-centralized supply and sanitation system [Weber et al., 2005]
ConclusionThe infrastructure of water supply and sanitation systems is deficient in the ma-jority of the rapidly growing cities in developing and emerging nations. The well developed big cities do not only have problems with insufficient infrastructure, but also with the necessary extension measures and regular maintenance of the current infrastructure. Thus, it is important to evaluate, how the infrastructure development can keep up with the city's rapid growth. The sustainability of city and infrastructure development should be considered in the progress. Semi-centralized supply and sanitation systems, which are based on nutrient recycling and water reuse in relatively small units, may be a suitable ecological, economi-cal and sustainable solution for the big cities. It is not possible to determine a standard size for semi-centralized systems. It is rather necessary to evaluate the size for each big city under investigation, thereby taking into account the local boundary conditions (e.g. population, size of city area) and individual needs.
Furthermore it has to be considered that the spatial, administrative and juridical frameworks of a developing area take serious influence on the optimal size. The calculated size from 50,000 up to 100,000 inhabitants of the ’ideal development size‘ is based on several model-assumptions which have to be depleted by the actual figures of the actual development area. The specific local and regional parameters determine the recommendable size of the supply- and disposal-area on the one and the choice of the best-possible adopted treatment methods udn techniques on the other hand. Generally it can be acted in consumption that the calculated developing-size from 50,000 up to 100,000 inhabitants is reliable in terms of a guide value or benchmark.
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8 Semi-centralized water systems for rapidly growing urban areas
Acknowledgement The authors want to thank the German Ministry of Education and Research for the founding of the research project “Semi-centralized supply and treatment sys-tems for urban areas in China”. This project was the fundament of the present paper.
References Abhat, D. Dineen, S.; Jones, T,; Motavalli, J. ; Sanborn, R. ; Slomkowski, K. (2005):
Cities of the Future – Today’s “Mega-cities” are Overcrowded and Environmentally Stressed, Environmental Magazine, Volume XVI, Number 5, September/October 2005
Bismas, A. K.; Tortajada, C. (2004): The water challenges of Megacities, Third World Centre for Water Management; Professor Jan Lundqvist, SIWI; and Dr. Olli Varis, Helsinki University of Technology
Cornel (2003); “Semicentralized supply and treatment systems for urban areas in China” Research project, financed by the German Ministry of Education and Research, pro-ject number: 02WD0607
Cornel and Wagner (2002): Decentralized Sanitation Concepts for Urban Areas, presen-tation at EET Paris, 17th Nov. 2002
Cornel, P.; Wagner, M.; Weber, B. (2004): Semi-centralized Sanitation Concepts for Urban Areas in China, not published, Institut WAR, TU Darmstadt, 2004
Cross, P.; Morel, A (2004): Pro-poor strategies for urban water supply and sanitation services delivery in Africa, Water and Sanitation Program Africa, Abstract Volume, the 14th Stockholm Water Symposium August 16th – 20th 2004
Dhakal, S. (2002): Mega--Cities in Asia: An (Un) Sustainable Development?, interna-tional science roundtable for the media – 4th June 2002, Bali, Indonesia
Perlman, J.; Hopking, E.; Jonsson, Å (1998): Urban solutions at the poverty/Environment intersection, the Mega-Cities Project, Publication MCP – 018, 1998
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t
resi
dual
was
te w
ater
energy
resi
dual
was
teS
uppl
y an
d T
reat
men
t Uni
tw
aste
wat
er
was
te
potable water
service water
raw
wat
er
was
te
trea
tmen
t w
aste
wat
er
trea
tmen
t
wat
er
trea
tmen
t
was
te
trea
tmen
t w
aste
wat
er
trea
tmen
t
wat
er
trea
tmen
t
was
te
trea
tmen
t w
aste
wat
er
trea
tmen
t
wat
er
trea
tmen
t
resi
dual
was
te w
ater
energy
resi
dual
was
te
•on
e un
itof
a s
emi-c
entra
lized
san
itatio
n sy
stem
(s
uppl
y an
d tre
atm
ent)
Inst
itute
16
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
raw
wat
er(s
urfa
cew
ater
)
rece
ivin
gst
ream
/us
e
blac
kw
ater
proc
ess
wat
er
grey
wat
er
ener
gy
lact
icac
id
resi
due
was
te
proc
ess
was
tew
ater
wat
erw
orks
sew
age
slud
ge
Lege
nde
drin
king
wat
erpu
rific
atio
n
grey
wat
er
blac
kw
ater
proc
ess
was
tew
ater
proc
ess
wat
er
wat
erw
orks
sew
age
ener
gy
was
te
end
prod
uct
mat
eria
l flo
ws
treat
men
tste
p
drin
king
wat
erpu
rific
atio
nw
aste
hand
ling
blac
kw
ater
treat
men
t
grey
wat
ertre
atm
ent
raw
wat
er(s
urfa
cew
ater
)
rece
ivin
gst
ream
/us
e
blac
kw
ater
proc
ess
wat
er
grey
wat
er
slud
geener
gy
lact
icac
id
resi
due
was
te
proc
ess
was
tew
ater
wat
erw
orks
sew
age
Lege
nde
drin
king
wat
erpu
rific
atio
n
grey
wat
er
blac
kw
ater
proc
ess
was
tew
ater
proc
ess
wat
er
wat
erw
orks
sew
age
ener
gy
was
te
end
prod
uct
mat
eria
l flo
ws
treat
men
tste
p
drin
king
wat
erpu
rific
atio
ndr
inki
ngw
ater
treat
men
tw
aste
hand
ling
was
teha
ndlin
gw
aste
hand
ling
blac
kw
ater
treat
men
tbl
ack
wat
ertre
atm
ent
grey
wat
ertre
atm
ent
grey
wat
ertre
atm
ent
grey
wat
ertre
atm
ent
inte
grat
edsy
stem
- 290 -
Inst
itute
17
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
raw
wat
er(s
urfa
cew
ater
)
rece
ivin
gst
ream
/us
e
blac
kw
ater
proc
ess
wat
er
grey
wat
er
ener
gy
lact
icac
id
resi
due
was
te
proc
ess
was
tew
ater
wat
erw
orks
sew
age
slud
ge
Lege
nde
drin
king
wat
erpu
rific
atio
n
grey
wat
er
blac
kw
ater
proc
ess
was
tew
ater
proc
ess
wat
er
wat
erw
orks
sew
age
ener
gy
was
te
end
prod
uct
mat
eria
l flo
ws
treat
men
tste
p
drin
king
wat
erpu
rific
atio
nw
aste
hand
ling
blac
kw
ater
treat
men
t
grey
wat
ertre
atm
ent
raw
wat
er(s
urfa
cew
ater
)
rece
ivin
gst
ream
/us
e
blac
kw
ater
proc
ess
wat
er
grey
wat
er
slud
geener
gy
lact
icac
id
resi
due
was
te
proc
ess
was
tew
ater
wat
erw
orks
sew
age
Lege
nde
drin
king
wat
erpu
rific
atio
n
grey
wat
er
blac
kw
ater
proc
ess
was
tew
ater
proc
ess
wat
er
wat
erw
orks
sew
age
ener
gy
was
te
end
prod
uct
mat
eria
l flo
ws
treat
men
tste
p
drin
king
wat
erpu
rific
atio
ndr
inki
ngw
ater
purif
icat
ion
was
teha
ndlin
gw
aste
hand
ling
was
teha
ndlin
g
blac
kw
ater
treat
men
tbl
ack
wat
ertre
atm
ent
grey
wat
ertre
atm
ent
grey
wat
ertre
atm
ent
grey
wat
ertre
atm
ent
Inst
itute
18
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
Wat
er s
uppl
y•
use
of g
roun
d w
ater
is o
ften
forb
idde
n es
peci
ally
in
urba
n ar
eas,
bec
ause
of s
carc
e vo
lum
e pr
oble
ms:
un
derg
roun
d su
bsid
ence
, sal
t wat
er in
trusi
on
•av
aila
ble
rain
wat
erby
rain
wat
er h
arve
stin
g sa
tisfie
s on
ly a
third
of t
he n
eede
d am
ount
for t
oile
t flu
shin
g,
but i
s us
eabl
e fo
r irr
igat
ion
and
stre
et c
lean
ing
•be
caus
e of
the
reus
e of
wat
er th
ere
is a
sav
ing
of ta
p w
ater
Inst
itute
19
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
raw
wat
er(s
urfa
cew
ater
)
rece
ivin
gst
ream
/us
e
blac
kw
ater
proc
ess
wat
er
grey
wat
er
ener
gy
lact
icac
id
resi
due
was
te
proc
ess
was
tew
ater
wat
erw
orks
sew
age
slud
ge
Lege
nde
drin
king
wat
erpu
rific
atio
n
grey
wat
er
blac
kw
ater
proc
ess
was
tew
ater
proc
ess
wat
er
wat
erw
orks
sew
age
ener
gy
was
te
end
prod
uct
mat
eria
l flo
ws
treat
men
tste
p
drin
king
wat
erpu
rific
atio
nw
aste
hand
ling
blac
kw
ater
treat
men
t
grey
wat
ertre
atm
ent
raw
wat
er(s
urfa
cew
ater
)
rece
ivin
gst
ream
/us
e
blac
kw
ater
proc
ess
wat
er
grey
wat
er
slud
geener
gy
lact
icac
id
resi
due
was
te
proc
ess
was
tew
ater
wat
erw
orks
sew
age
Lege
nde
drin
king
wat
erpu
rific
atio
n
grey
wat
er
blac
kw
ater
proc
ess
was
tew
ater
proc
ess
wat
er
wat
erw
orks
sew
age
ener
gy
was
te
end
prod
uct
mat
eria
l flo
ws
treat
men
tste
p
drin
king
wat
erpu
rific
atio
ndr
inki
ngw
ater
treat
men
tw
aste
hand
ling
was
teha
ndlin
gw
aste
hand
ling
blac
kw
ater
treat
men
tbl
ack
wat
ertre
atm
ent
grey
wat
ertre
atm
ent
grey
wat
ertre
atm
ent
grey
wat
ertre
atm
ent
Inst
itute
20
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
was
te w
ater
trea
tmen
t•
grey
wat
er:
was
te w
ater
from
sho
wer
s an
d ba
thtu
bs, h
and
basi
ns a
nd
was
hing
mac
hine
s
•bl
ack
wat
er:
was
te w
aste
r fro
m to
ilette
s flu
shin
g an
d ki
tche
n
afte
r tre
atm
ent:
•tr
eate
d gr
ey w
ater
: se
rvic
e w
ater
for u
sing
in p
rivat
e ho
useh
old
or
•tr
eate
d bl
ack
wat
er: d
isch
arge
or r
euse
in u
rban
zon
es
•sl
udge
: com
bine
d tre
atm
ent w
ith re
sidu
al w
aste
- 291 -
Inst
itute
21
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
cera
mic
m
embr
ane sl
udge
prec
ipita
tion
/floc
cula
tion
fine
scre
en
scre
enin
gs
stor
age
prec
ipita
nts
/floc
cula
nts
stor
age
„Gre
y w
ater
co
ncen
trat
es“
MB
R I
slud
gebl
ower
UV-
Dis
infe
ctio
n
Backwash water
blow
er
efflu
ent
efflu
ent
efflu
ent
efflu
ent
MB
R II
slud
gebl
ower
efflu
ent
SBR
slud
ge
UV-
Dis
infe
ctio
n
stor
age
with
co
ld /w
arm
ag
greg
ate
biol
ogic
al
sand
filte
r
influ
ent
cera
mic
m
embr
ane sl
udge
prec
ipita
tion
/floc
cula
tion
fine
scre
en
scre
enin
gs
fine
scre
en
scre
enin
gs
stor
age
prec
ipita
nts
/floc
cula
nts
stor
age
„Gre
y w
ater
co
ncen
trat
es“
MB
R I
slud
gebl
ower
blow
er
UV-
Dis
infe
ctio
n
Backwash water
blow
er
efflu
ent
efflu
ent
efflu
ent
efflu
ent
MB
R II
slud
gebl
ower
blow
er
efflu
ent
SBR
slud
ge
UV-
Dis
infe
ctio
n
stor
age
with
co
ld /w
arm
ag
greg
ate
biol
ogic
al
sand
filte
r
influ
ent
Inst
itute
22
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
mix
ing
stat
ion
grey
wat
er
biof
ilter
Inst
itute
24
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
•SB
R T
haila
nd W
ater
hous
e
- 292 -
Inst
itute
25
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
raw
wat
er(s
urfa
cew
ater
)
rece
ivin
gst
ream
/us
e
blac
kw
ater
proc
ess
wat
er
grey
wat
er
ener
gy
lact
icac
id
resi
due
was
te
proc
ess
was
tew
ater
wat
erw
orks
sew
age
slud
ge
Lege
nde
drin
king
wat
erpu
rific
atio
n
grey
wat
er
blac
kw
ater
proc
ess
was
tew
ater
proc
ess
wat
er
wat
erw
orks
sew
age
ener
gy
was
te
end
prod
uct
mat
eria
l flo
ws
treat
men
tste
p
drin
king
wat
erpu
rific
atio
nw
aste
hand
ling
blac
kw
ater
treat
men
t
grey
wat
ertre
atm
ent
raw
wat
er(s
urfa
cew
ater
)
rece
ivin
gst
ream
/us
e
blac
kw
ater
proc
ess
wat
er
grey
wat
er
slud
geener
gy
lact
icac
id
resi
due
was
te
proc
ess
was
tew
ater
wat
erw
orks
sew
age
Lege
nde
drin
king
wat
erpu
rific
atio
n
grey
wat
er
blac
kw
ater
proc
ess
was
tew
ater
proc
ess
wat
er
wat
erw
orks
sew
age
ener
gy
was
te
end
prod
uct
mat
eria
l flo
ws
treat
men
tste
p
drin
king
wat
erpu
rific
atio
ndr
inki
ngw
ater
treat
men
tw
aste
hand
ling
was
teha
ndlin
gw
aste
hand
ling
blac
kw
ater
treat
men
tbl
ack
wat
ertre
atm
ent
grey
wat
ertre
atm
ent
grey
wat
ertre
atm
ent
grey
wat
ertre
atm
ent
Inst
itute
26
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
was
te tr
eatm
ent
prob
lem
: mai
n pr
oduc
t of a
naer
obic
was
te tr
eatm
ent (
ther
mal
en
ergy
from
the
biog
as) h
as n
o pr
efer
able
use
r und
er th
e gi
ven
spat
ial s
ituat
ion
(mon
o fu
nctio
nal h
abita
tion)
solu
tion:
opt
imiz
atio
n of
pro
cess
con
trol f
or th
e ge
nera
tion
of
othe
r pro
duct
s, e
.g. l
actic
aci
d. T
he te
chno
logy
is a
co
mbi
natio
n of
cla
ssic
al a
naer
obic
was
te tr
eatm
ent a
nd s
ilage
pr
oduc
tion
proc
esse
s
chal
leng
es: p
roce
ss c
ontro
l for
mon
o su
bstra
tes
is w
ell
know
n an
d st
ate
of th
e ar
t tec
hnol
ogy
in C
ontra
st, o
rgan
ic w
aste
is v
ery
inho
mog
eneo
us a
nd
inco
nsta
nt in
it‘s
com
posi
tion
Inst
itute
27
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
Pilo
t Pla
nt fo
r lac
tic a
cid
ferm
enta
tion
inpu
t pr
epar
atio
nre
acto
rou
tput
biog
as e
xhau
st
Inst
itute
28
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
raw
wat
er(s
urfa
cew
ater
)
rece
ivin
gst
ream
/us
e
blac
kw
ater
proc
ess
wat
er
grey
wat
er
ener
gy
lact
icac
id
resi
due
was
te
proc
ess
was
tew
ater
wat
erw
orks
sew
age
slud
ge
Lege
nde
drin
king
wat
erpu
rific
atio
n
grey
wat
er
blac
kw
ater
proc
ess
was
tew
ater
proc
ess
wat
er
wat
erw
orks
sew
age
ener
gy
was
te
end
prod
uct
mat
eria
l flo
ws
treat
men
tste
p
drin
king
wat
erpu
rific
atio
nw
aste
hand
ling
blac
kw
ater
treat
men
t
grey
wat
ertre
atm
ent
raw
wat
er(s
urfa
cew
ater
)
rece
ivin
gst
ream
/us
e
blac
kw
ater
proc
ess
wat
er
grey
wat
er
slud
geener
gy
lact
icac
id
resi
due
was
te
proc
ess
was
tew
ater
wat
erw
orks
sew
age
Lege
nde
drin
king
wat
erpu
rific
atio
n
grey
wat
er
blac
kw
ater
proc
ess
was
tew
ater
proc
ess
wat
er
wat
erw
orks
sew
age
ener
gy
was
te
end
prod
uct
mat
eria
l flo
ws
treat
men
tste
p
drin
king
wat
erpu
rific
atio
ndr
inki
ngw
ater
treat
men
tw
aste
hand
ling
was
teha
ndlin
gw
aste
hand
ling
blac
kw
ater
treat
men
tbl
ack
wat
ertre
atm
ent
grey
wat
ertre
atm
ent
grey
wat
ertre
atm
ent
grey
wat
ertre
atm
ent
inte
grat
edsy
stem
- 293 -
Inst
itute
29
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
high
den
sity
hous
ing
area
s(h
ousi
ngw
ithup
to 6
st
orey
spr
oper
)-4
2% -
low
desi
tyho
usin
gar
eas
(sin
gle-
fam
ilyan
d tw
o-fa
mily
hous
esw
ithup
to
2 st
orey
spr
oper
)-8
% -
mod
erat
e de
nsity
hous
ing
area
s(h
ousi
ngw
ithup
to 4
st
orey
spr
oper
)-6
% -
gene
ralp
ublic
dem
and
area
(soc
iali
nfra
stru
ctur
eas
w
ell a
s su
pply
and
di
spos
alce
nter
)-8
% -
acce
ssro
ad(1
st a
nd 2
nd o
rder
)
tota
l are
a50
0.00
0 m
²
gree
nsp
ace
-16%
-
13.0
00 re
side
nts
high
den
sity
hous
ing
area
s(h
ousi
ngw
ithup
to 6
st
orey
spr
oper
)-4
2% -
low
desi
tyho
usin
gar
eas
(sin
gle-
fam
ilyan
d tw
o-fa
mily
hous
esw
ithup
to
2 st
orey
spr
oper
)-8
% -
mod
erat
e de
nsity
hous
ing
area
s(h
ousi
ngw
ithup
to 4
st
orey
spr
oper
)-6
% -
gene
ralp
ublic
dem
and
area
(soc
iali
nfra
stru
ctur
eas
w
ell a
s su
pply
and
di
spos
alce
nter
)-8
% -
acce
ssro
ad(1
st a
nd 2
nd o
rder
)
tota
l are
a50
0.00
0 m
²
gree
nsp
ace
-16%
-
13.0
00 re
side
nts
13,0
00 re
side
nts
Mod
el C
ell
tota
l are
a50
0,00
0 m
²
Inst
itute
30
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
1
Mod
el-c
ell w
ith 1
3,00
0 re
siden
ts
Loca
tion
of s
uppl
y an
d di
spos
al c
entre
23a 3b
4a 4b5
(b)
mod
elin
g re
com
men
dabl
e di
men
sion
s of
spa
ce a
nd re
side
nts
Inst
itute
31
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
Exam
ple:
City
of Q
ingd
aoEx
ampl
e: C
ity o
f Qin
gdao
Inst
itute
32
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
- 294 -
Inst
itute
33
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
Inst
itute
34
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
Cur
rent
rese
arch
sta
tus
•in
tegr
ated
sup
ply
and
disp
osal
sys
tem
s of
a s
ize
betw
een
50,0
00 a
nd 1
00,0
00 re
side
nts
shou
ld b
e pr
efer
red
actu
al re
sear
ch
•op
timis
ing
tech
nica
l con
cept
s
•de
velo
ping
inte
grat
ed p
lann
ing
and
appr
oval
pro
cess
es fo
r in
tegr
ated
sem
i-cen
traliz
ed s
uppl
y an
d di
spos
al s
yste
ms
Inst
itute
35
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
Key
Que
stio
ns
•is
the
idea
feas
ible
to m
ake
deve
lopm
ent i
n fa
st g
row
ing
urba
n ar
eas
(mor
e) s
usta
inab
le?
•ar
e th
ere
othe
r stra
tegi
esto
reac
h su
stai
nabi
lity
(in c
ases
of
supp
ly a
nd d
ispo
sal s
yste
ms)
?
•w
hat a
re th
e ch
alle
nges
inin
tegr
ated
pla
nnin
gan
d ap
prov
al
proc
esse
s(fo
r org
anis
atio
nal r
easo
ns)?
Inst
itute
36
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
Ack
now
ledg
emen
t
Than
ks to
the
Min
istry
of E
duca
tion
and
Res
earc
h of
the
Fede
ral R
epub
lic o
f Ger
man
y fo
r the
foun
ding
of t
he
rese
arch
pro
ject
“Sem
i-cen
traliz
ed s
uppl
y an
d
treat
men
t sys
tem
s fo
r urb
an a
reas
in C
hina
”.
This
pro
ject
was
the
fund
amen
t of t
he
pres
ente
d pa
per
- 295 -
Inst
itute
37
Sem
i-cen
tral
ized
sup
ply
and
disp
osal
sys
tem
s fo
r fas
t gr
owin
g ur
ban
area
s in
Chi
na
Than
k yo
u fo
r you
r atte
ntio
n
Than
k yo
u fo
r you
r atte
ntio
n
- 296 -