z Messages from Departments and Centers of NILIM

Towards a new evolution for sewerage

PhotoSHIMIZU Toshiaki , Director
Water Quality Control Department(Key words) Stock management, sanitary safety, membrane bioreaction, greenhouse gases
1. Sewerage approaches a turning point
Sewerage works in Japan are approaching a major
turning point. Until now, the policy emphasis has beenon diffusion and expansion as a matter of pressing
concern. From now on, however, stress will steadily
shift towards safety and environment, with demands forproper management and operation. The basic tasksfacing sewerage amid this process may be outlined asfollows.
٤ Immediate tasks in developing sewerage
infrastructure¾ Eliminating areas that lack wastewater treatment
facilities¾ Addressing the frequent occurrence ofconcentrated torrential rains and the expansion offlood damage associated with climate change¾ Improving water quality in closed water areas
through high-grade treatment¾ Reducing risks to aquatic systems by improving
and upgrading sewerage functions related to publichygiene (e.g. improving combined sewerage)
٤ Tasks in terms of stock management¾ Risk management related to facility dilapidationand systematic asset management facilitating
sustainable management¾ Enhanced earthquake resistance of seweragefacilities and retention of functions in the event ofan earthquake٤ Tasks associated with demographic change¾ Dynamic revision of plans in response topopulation decline and aging, introducing efficientmethods of development and management¾ Strengthening
seweragemanagement
infrastructure¾ Contributing to vibrant regional development bymaking effective use of sewerage facilities andrecycled water٤ Tasks concerning the contribution to newenvironmental problems¾ Creating positive water environments byincreasing the soundness of water and substancecirculation systems¾ Helping to solve problems of global warming,
resources and energy by using the resources,
energy, etc., provided by sewerage
2. Research areas subject to priority efforts
In the field of sewerage research, we undertakepriority research with emphasis on the following areas.
In this way, we provide technical support for policies

that will form a pillar of national sewerageadministration in line with the basic directions of new
sewerage technology.
(1) Areas related to sewerage stock management
Sewerage stock management is a field that is
attracting attention internationally, as illustrated by thefact that reviews are in progress with a view to ISO
standardization. On the other hand, against a spate ofroad collapses and other incidents, there is increasing
concern over the proper management of sewer pipes.
Although pipe renewal and repair technology has
progressed tremendously in recent years, we need toaccurately grasp the state of deterioration of pipes, inorder to make effective use of these technologies. To
this end, we are conducting research in various areas
based on information from local authorities all overJapan. These include research to establish a formula forpredicting soundness that will provide a foundation for
estimating the volume of future modification works,
and research on methods of deciding priorities forsurveys and modification (Fig. 1).
(2) Areas related to sanitary safety of treatedwastewaterWith the spread of sewerage systems, the volume ofwater carried by them has steadily increased, and thishas had a relatively large impact on water environments.
Meanwhile, the roles of treated wastewater as a water
resource are expanding, as illustrated by its reuse inurban landscaping, recreational water, and so on. On
the other hand, there have been outbreaks of healthhazards caused by waterborne infectious pathogenic
microbes including protozoa and viruses. As a result,
there are demands that sanitary safety also be
guaranteed for treated wastewater, reflecting the role itplays in water environments. Therefore, we are
currently drawing up measures to ensure sanitary safetyin line with the state of water use and purpose of using
recycled water at sites of treated wastewater discharge,
in connection with the norovirus (Fig. 2). We have also
started studies on measures to address new types ofinfluenza virus that are feared likely to become
prevalent in connection with sewerage.
(3) Areas related to wastewater treatment using
membrane treatment technology
Treatment technology using membranes in theprocess of solid-liquid separation efficiently removes
microbes and has a strong capacity for retaining
activated sludge. This is therefore considered apromising technique that can not only improve water
treatment performance but also make treatment

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Fig. 1 Example of calculations for future works volumein a model city
(top: with simple modification after 50 years, bottom:
when using the formula for predicting soundness)

Residual rate (Ct/Co)

3. Further use of sewerage technology
Currently, activities designed to solve the world’s
water and sanitation problems and the problems ofglobal warming using sewerage technology
accumulated by Japan are being developed in the fieldof sewerage. The Global Center for Urban Sanitation(GCUS), a body representing the industrial, public andacademic sectors, was established for this purpose.
GCUS is now pursuing concrete studies based on thehypothesis of targeted countries and issues, and ourDepartment is playing a positive part by contributing totechnical aspects. Through this kind of initiative, weexpect that steps will be taken to diffuse sustainablesewerage systems based on accumulated Japanese
knowhow, from planning and construction tomanagement and operation; and that this, in turn, willassist the further development of Japan’s seweragetechnology.

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facilities more compact, make facility modification andrenewal smoother, save resources in operationalmanagement, and so on, thereby solving a number ofproblems currently facing wastewater treatment
facilities. Thus, as well as promoting objective
evaluation of the water treatment performance ofmembrane bioreaction (a combination of theconventional activated sludge with membrane
treatment technology), we are also looking into
technical issues and matters for study when attempting
to introduce it into actual facilities as a method oftreating wastewater.
(4) Areas related to reducing the burden on the global
environment
With the effectuation of the Kyoto Protocol, we are
expected to take initiatives to meet targets forgreenhouse gas reduction. While sewerage works are asource of greenhouse gas emissions, their rich potential
as resources and energy (such as treated wastewater andwastewater sludge) could contribute to solving thedepletion of resources and problems of the globalenvironment. We are currently studying this dual
relationship between sewerage and greenhouse gases,
with respect to reducing emissions of nitrous oxide
arising from the wastewater treatment process(mitigation measures), and the effect of reducing
greenhouse gases through recycled use of treatment
water (adaptation measures). Finally, we are also
studying the LCA technique in relation to seweragefacilities, with a view to accurately assessing theenvironmental burden arising from sewerage and theeffectiveness of countermeasures.

Length requiring
modification㧔km/year㧕ᡷ▽ᔅⷐᑧ㐳㧔MOᐕ㧕z Messages from Departments and Centers of NILIM

E.coliE.coli colony Norovirus
G1Norovirus
GIIFig. 2 Comparison of chlorine sterilization fornorovirus and E.coli