Study on the Clogging and Regulation Measures of Bioretention
Facilities in Sponge City
Yuan Zhou
1,2 a
, Long Yang
1,† b
, Siyu Wang
, Yangyang Chu
, Min Zhang
and Xiangchun Wang
China Urban Construction Design & Research Institute Co. Ltd, 100120, Beijing, China
State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua
University, 100120, Beijing, China
Keywords: Bioretention Facility, Green Stormwater Infrastructure, Sponge City, Clogging, Regulation Measures.
Abstract: Bioretention facilities play an important role in regulating runoff, purifying water quality and preventing
urban waterlogging. However, clogging is the common and restrict problem after long-term operation of
these facilities, which affects the effective operation and ecological benefits. Clogging causes and influence
factors of bioretention facilities were summarized in this work. And corresponding regulation measures of
bioretention facilities in sponge city were studied systematically from five aspects: source control, operation
design, media optimization, vegetation selection, and management. A series of optimization measures were
recommended, such as apply novel snowmelt agents, add pre-treatment process, improve filter materials,
optimize plant species, update damaged cover and vegetation, and build a dynamic monitoring system. This
work could provide alternative strategies for the long-term operation of bioretention facilities, which play a
vital role in regulating runoff, purifying water quality and improving the construction of sponge city.
Bioretention facility is one of the representative
measures of low-impact development and sponge
city construction, which can alleviate runoff
pollution, purify water quality, reduce the amount of
surface runoff and peak flow (Skorobogatov 2020).
Bioretention facilities mainly include bioretention
zone, rain garden, flower bed, biofilter trench and
ecological tree pond. Rainwater runoff contains a
variety of pollutants such as suspended solids (SS),
nitrogen and phosphorus, pathogenic bacteria, heavy
metals, snowmelt agents, pesticides and herbicides
(Zhang 2019). During the long-term operation,
bioretention facilities face some problems such as
excessive erosion, pollutants accumulation, media
clogging and plant death. And clogging has become
one of the most common and vital problems in the
operation process of bioretention facilities (Tang
2017, Costello 2020, William 2019).
At present, many researches have focused on the
percolation performance, filler composition, plant
selection, model simulation and so on (Jiang 2019,
Andrew 2021). Li put forward improvement and
management suggestions for the construction
problems of bioretention facilities, such as
inconsistent construction with drawings and poor
drainage (Li 2020). However, researches on the
causing and influence factors of clogging and their
regulation methods of bioretention facilities are still
scattered. In this paper, the reasons and factors of
clogging that affected the operation of bioretention
facilities were systematically summarized, and the
regulation measures to optimize were
comprehensively proposed, which could provide a
reference for the actual operation of green
stormwater infrastructure in sponge city.
After long-time operation of bioretention facilities,
media clogging is one of the common problems and
Zhou, Y., Yang, L., Wang, S., Chu, Y., Zhang, M. and Wang, X.
Study on the Clogging and Regulation Measures of Bioretention Facilities in Sponge City.
DOI: 10.5220/0011508900003443
In Proceedings of the 4th International Conference on Biomedical Engineering and Bioinformatics (ICBEB 2022), pages 1302-1307
ISBN: 978-989-758-595-1
2022 by SCITEPRESS Science and Technology Publications, Lda. All rights reserved
the water quality can’t meet the design requirements.
Permeability is used to characterize the clogging
degree of bioretention facilities (Ding 2019). In the
field investigation of bioretention facilities after
operation for 4 years, it was found that clogging
problem existed in 40% of the time during the
operation of the facilities (Coustumer 2012). The
causes and processes of clogging are complex and
simultaneous, which can be mainly divided into
physical clogging, chemical clogging and biological
Physical clogging SS is the representative reason
of physical clogging, causing inorganic and organic
clogging (Conley 2020). Researches showed that the
main reason for inorganic clogging was suspended
particles with a particle size above 5 μm, and most
of them were inorganic minerals (e.g. quartz,
feldspar and other non-expansive minerals), which
could permeate with rainwater runoff and easily be
trapped on the surface of medium due to filtration
(Kandra 2017). SS with particle size during 0.22 μm
-5 μm could lead to organic clogging (Kandra 2017).
Chemical clogging When rainwater runoff with
complex composition entered bioretention facilities,
it would cause changes in pH value, the contents of
carbonate and other chemical components of water,
resulting in precipitation of salt, iron and calcium
ions, and then forming chemical clogging (Wang
2012, Raham 2020). Studies found that TDS of
runoff in grassland and congested road surface was
pretty high, including bicarbonate and calcium ions,
leading to the risk of chemical clogging (Raham
2020). Kakuturu also found that NaCl could affect
permeability of facility and plant health, resulting in
clogging of bioretention system (Kakuturu 2015).
Biological clogging Under suitable conditions,
microorganisms in the facility could multiply rapidly
and form biofilms, which blocked the pores of filler
and reduced the water conductivity of aquifers (Liu
2017). Organic matters such as humus and fulvic
acid-like terrestrial organic matters, as well as
proteins were their original sources. Besides
microorganisms themselves, extracellular polymers
(EPS) secreted by microorganisms could also lead to
biological clogging. When the content of TOC in
runoff was higher than 25 mg/L, it was beneficial to
the large-scale reproduction of microorganisms and
secretion of EPS, resulting in a high risk of
biological clogging (Chris 2013).
3.1 Structure and Operation Mode
The structural characteristics of bioretention
facilities (e.g. submerged area, layered packing) and
the operation mode (e.g. wet-dry alternation, up-
flow mode) have vital influence on the clogging of
the facilities. Studies showed that high initial
permeability of facility, small thickness of media
layer, setting of submerged area and large particle
matters could aggravate the clogging of bioretention
facilities (Chen 2013, Read 2008). Many studies
demonstrated that dry-wet alternation can
significantly improve the oxygen supply conditions,
improve the removal of pollutants, enhance
permeability of the system, and thus effectively
control the clogging of facility (Jiang 2017, Pan
2020). In addition, it was found that the structure of
layered media effectively prolonged the time of
clogging, forming the aerobic-anaerobic conditions
and promoting denitrification to increase nitrogen
removal (Chen 2013, Li 2014). However, some
studies showed that the mixed packing may enhance
the connectivity of pore space and improve
hydraulic conductivity of the facility compared with
the layered media (Lefevre 2015). Zhang et al
(Zhang 2019) indicated that up-flow and mixed-flow
bioretention facility could delay the clogging time
by extending the path of runoff and hydraulic
retention time.
3.2 Media and Filler
Media is one of the important factors that affect the
pollution control and clogging problem in the
bioretention facilities. The characteristics of the
media, such as the degree of compaction, the
thickness of the filter layer and whether to add
carbon source, could all influence the permeability
of the bioretention system (Tian 2018, Qiu 2017).
Media compaction could increase the bulk density,
limit the penetration of plant roots, and lead to a
significant decrease in media permeability (Tian
2018). Study founded that sandy soil could bear
compaction while its infiltration rate decreased
significantly after compaction. As for clay soil, its
compaction and water saturation had both low
permeability (Qiu 2017). In addition, many studies
indicated that adding organic matters into filler
composition not only provided carbon source for
denitrification, but also provided carriers for
Study on the Clogging and Regulation Measures of Bioretention Facilities in Sponge City
microorganisms, promoting the proliferation of
microorganisms, thus significantly reducing the bulk
density of media (Li 2019, Mu 2020). Additives
such as organic compost, biochar, sawdust, straw,
agricultural wastes could improve the penetration
rate and water holding capacity of media. For
example, adding biochar into media had a good
performance in hydrological effect and nitrogen
removal in the bioretention system (Mu 2020).
3.3 Vegetation
Vegetation played an irreplaceable role in
bioretention facilities, but the influence of vegetation
on clogging of bioretention system was complex and
controversial (Yu 2019, Knowles 2011, Hua 2014).
Some researchers pointed out that vegetation could
delay the clogging of the facility, on one hand,
vegetation could slow down the flow velocity of
runoff and reduce SS. On the other hand, the growth
of plant roots could promote the reproduction of
microbial communities and affected the activity of
rhizosphere microorganism, which were beneficial
to the degradation of pollutants, maintenance of
infiltration rate and prevention of clogging. Results
showed that plants in bioretention facilities,
especially those with thick and deep taproot, played
an important role in maintaining the permeability of
facilities (Yu 2019).
However, some researchers believed that plants
contributed to more organic matters, thus
accelerating the clogging of the system. Kadlec
(Knowles 2011) found that 5%-15% of plant
residues was difficult to degrade, which was easy to
cause clogging. Hua (Hua 2014) indicated that
plants played different roles in the whole clogging
process of bioretention facility. In the early stage,
plant roots restricted water flow, while in the later
stage, growing roots opened new pore spaces to
improve permeability. Therefore, it is necessary to
consider the combination of vegetation in order to
improve the efficiency of pollutant removal and
alleviate the clogging of bioretention system.
3.4 Microorganism
The pores in the bioretention system could easily be
blocked by the propagation of microorganisms in
bioretention facilities. Studies pointed out that
microorganisms such as algae and bacteria would
accumulate on the surface of the bioretention media,
and the reproduction of microorganisms greatly
reduced the permeability coefficient of the system
(Hua 2014). With the proliferation of
microorganisms, the pore volume in the media
gradually decreased. Microorganisms and their
metabolites could block the gaps in the bioretention
facility and reduce the permeability coefficient of
system. The specific growth rate of microorganisms,
substrate concentration and initial concentration of
soil microorganisms all could limit permeability
reduction. Robert confirmed that the development of
clogging was highly related to the total biological
oxygen demand and the cumulative mass density
load of SS.
4.1 Source Control
As a result of steel and chemical production
activities, atmospheric deposition, tire wear, exhaust
emissions and the use of pesticides, herbicides,
deicing agents, etc. A large number of pollutants
would enter the bioretention facilities with rainwater
runoff, including SS, TN, TP, metal ions, and
organic pollutants, etc. Many researchers indicated
that the spatial and temporal distribution of rainfall
runoff, pollutant concentration, underlying surface
types and rainfall characteristics including intensity,
duration and frequency, had great influence on
clogging of bioretention facilities (Jiang 2017, Read
2008). For example, higher concentration of influent
and higher rainfall intensity could more easily lead
to clogging of bioretention facility (Jiang 2017). For
reducing the influence of 54rainwater runoff on
clogging, environmentally friendly chemicals such
as biological pesticides, biological attractants, and
snowmelt agents should be used to reduce the
accumulation and improve their own degradation.
Different clean deicers should be rationally selected
according to road conditions, temperature, design of
pretreatment diversion should be carried out.
4.2 Operation Design
In order to prevent the clogging and accumulation of
pollutants in the bioretention facilities, it is
necessary to take into account their structural
characteristics and functions. Factors such as rainfall
recurrence period, pretreatment process, operation
mode, pollutant load, hydraulic retention time, and
design of submergence zone were suggested
(Coustumer 2012, Li 2019). For example,
appropriate dry period was conducive to the
ventilation of substrate and rapid degradation of
organic matter. It was found that the permeability
ICBEB 2022 - The International Conference on Biomedical Engineering and Bioinformatics
and hydraulic conductivity of the facility could be
improved and the clogging problem could be
alleviated by setting the submergence zone (Tian
2018). The addition of pretreatment facilities such as
pre-ponds and vortex ponds would remove large
particles in runoff ahead of time, slowed down the
flow rate and prevented the snowmelt from entering
directly into the infiltration area in winter (Chris
2013). For serious pollution and salinization of soil
caused by rainwater runoff areas, measures should
be taken to discard the flow and salt drainage.
4.3 Media Optimization
In order to alleviate clogging, measures of media
optimization mainly include three aspects:
combination and proportion of fillers, organic
carbon source addition, and filling mode (Tian 2018,
Qiu 2017, Li 2019), shown as Table 1. It is often
necessary to improve the ratio of fillers or to add
additives. The selection of the fillers should follow
the principles of easy to obtain, moderate cost, local
applicability, and have good permeability, large
specific surface area and good decontamination
ability, such as zeolites, vermiculites, fly ash, perlite,
aluminum sludge and river sediments. New
functional fillers like reed, biochar and recycled
aggregates were also recommended to improve the
permeability of facilities (Tian 2018, Qiu 2017).
Proper addition of carbon sources can increase the
permeability of bioretention facilities and effectively
alleviate their clogging. However, it was also
pointed out that excessive addition of carbon source
could increase the background value of phosphorus,
leading to release of phosphate and worsening water
quality (Li 2019). Therefore, the dosage of organic
matter should be strictly controlled, and the US
design manual recommended that the content of
organic matter in the packing should not exceed 5%.
Table 1: Media optimization for bioretention facilities.
Measures Composition
combination and proportion of
sand and fly ash
aluminum sludge and zeolite
sand, perlite, vermiculite
volcanic rock, spongy iron
vermiculite, zeolite, sand
organic carbon source addition
biochar, activated carbon
recycled building aggregates
compost, newspaper, sawdust,
filling mode
layered packing
mixed packing
4.4 Vegetation Selection
In general, vegetation in bioretention facilities
should be reasonably allocated according to their
cold and drought tolerance, soil permeability and
type, facility scale and structure, and runoff water
quality (Mu 2020, Yu 2019). The following aspects
should be paid attention to when selecting vegetation
in different bioretention facilities: (i) local species
should be the main species, the remaining species
could be matched reasonably, and the plants with
strong adaptability should be selected preferably; (ii)
plants with well-developed roots, large stems and
leaves that can penetrate through soil layer, strong
cold-resistance and drought-resistance, strong
purification ability are preferred; (iii) plants that can
accumulate pollutants such as heavy metals are
preferred; (iv) plants with large biomass and short
growth cycle are selected; (v) low maintenance cost,
certain economic value and landscape effect, and the
diversity of plant landscape in different seasons
should be considered.
Study on the Clogging and Regulation Measures of Bioretention Facilities in Sponge City
At present, the design and construction standards of
sponge city construction in China are established,
but the operation and maintenance of bioretention
facilities still lack (Yin 2021, Yang 2020, Mu 2020).
In order to ensure the treatment effect of
bioretention facilities, prevent clogging and achieve
long-term stability of facilities, the following
measures are recommended: (i) regular inspection
and dredge of garbage and sediment in the spillway,
and regular cleaning of the sand deposit; (ii) regular
vegetation maintenance according to the condition
of plants growth and soil humidity; (iii) to clean or
replace the surface fillers regularly and slow down
the growth of microorganisms; (iv) to take plant
anti-freezing measures and appropriate cover in the
packed bed to slow down the freezing rate in winter.
In addition, it should be monitored throughout the
whole process according to the runoff process,
realizing dynamic monitoring and intelligent
management through the on-line monitoring, digital
information platform and wireless network (Yang
As a representative measure in construction of
sponge city, bioretention facilities faced clogging
after long-term operation and maintenance,
therefore, it was of guiding significance to analyse
the reasons and influence factors of clogging in
facilities and put forward corresponding solutions.
This paper sorted out the control measures and
suggestions from combination of source reduction,
process optimization and operation management,
providing reference for long-term stability and
operation for green storm water infrastructure in
sponge city:
(i) The causes and processes of clogging were
complex and simultaneous, including physical
clogging, chemical clogging and biological
clogging, which mainly caused by SS, inorganic
ions, TOC, microorganisms and their EPS.
(ii) Utilization of environment-friendly
chemicals, optimization of structure by pretreatment
process, modified fillers, reasonable planting of
vegetation, maintenance and monitoring system
were suggested to improve facility performance and
alleviate clogging.
(iii) Combination of plant, microorganism,
pollutant migration mechanism to solve the problem
of clogging; prediction and model simulation of
clogging time; as well as monitoring methods and
equipment of clogging need further development.
This work was supported by the the Science
Foundation of China Urban Construction Design &
Research Institute Co., Ltd. (Y09S21009), and and
the Science and Technology Planning Project of
Ministry of Housing and Urban-Rural Development
of the People’s Republic of China (No. 2019-K-142)
for financial support.
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Study on the Clogging and Regulation Measures of Bioretention Facilities in Sponge City