38
yet functioning. The task team set our target as affordable treatment, which can be
applied in the rehabilitation stage before the full recovery of the treatment plants.
The MLIT, in charge of sewer systems, insisted on adding chlorine to the
untreated wastewater to meet the coliform standard for effl uent. However, this policy does not work for microbial water safety because chlorine is not effective against
all pathogens, including viruses and protozoa. The task team pointed out the weak
point in that policy, and tried to fi nd alternate ways to achieve a relatively safe water
environment.
Our concept was that given the urgent situation the treatment would not be perfect, but should be affordable. Usually wastewater is treated biologically over a relatively long retention time, but in this unusual case physicochemical treatment might
be better able to achieve microbially safe water in a short time. Instead, the target
among the water quality parameters should be narrowed down only to pathogen
control, which is more urgent and important under the circumstances in a disaster
area (Actually, on some occasions, nutrient or organic loading is not always harmful
to the environment, but pathogens have to be removed in any case).
Our experience was useful in searching for an appropriate treatment for storm
water combined with untreated wastewater, which is discharged into open bodies of
water when the sewer overfl ows due to an overabundance of rainwater. A combination of coagulation-sedimentation and ultraviolet disinfection was tested and found
to be the most effective method for producing relatively safe water.
Polysulfuric ferrite, a waste byproduct from the iron and steel industry, was
selected as the coagulant. It was also used as an anti-odor agent for municipal wastewater. Polysulfuric ferrite is used for organic wastewater treatment in the food
industry, among others. The proposed method successfully removed suspended solids and turbidity from the infl uent, and achieved a good amount of bacterial and
viral removal when used together with ultraviolet light disinfection. This result was
presented at a wastewater works conference.
Our method was not applied in reality in Ishinomaki City because it requires
waste sludge management after the coagulation and sedimentation. The sludge
management system was restored almost at the same time as the other water
treatment facilities, and the wastewater treatment plants selected a biological
treatment. The method the task team developed will be used in the future or in
other recovery areas in the Tohoku region. The sampling campaign for water
quality in the coastal area is still contributing to future water quality management
plans from the viewpoint of microbial water safety. During the course of the
project, much support was given to us by senior professors, stakeholders, and
laboratory staff. Overall the author experienced a strong leadership applied under
such a tragic disaster by integration of multi-stakeholders and application of scientifi c Knowledge.
Open Access This article is distributed under the terms of the Creative Commons
Attribution Noncommercial License which permits any noncommercial use, distribution,
and reproduction in any medium, provided the original author(s) and source are credited.
T. Akiyama et al.
yet functioning. The task team set our target as affordable treatment, which can be
applied in the rehabilitation stage before the full recovery of the treatment plants.
The MLIT, in charge of sewer systems, insisted on adding chlorine to the
untreated wastewater to meet the coliform standard for effl uent. However, this policy does not work for microbial water safety because chlorine is not effective against
all pathogens, including viruses and protozoa. The task team pointed out the weak
point in that policy, and tried to fi nd alternate ways to achieve a relatively safe water
environment.
Our concept was that given the urgent situation the treatment would not be perfect, but should be affordable. Usually wastewater is treated biologically over a relatively long retention time, but in this unusual case physicochemical treatment might
be better able to achieve microbially safe water in a short time. Instead, the target
among the water quality parameters should be narrowed down only to pathogen
control, which is more urgent and important under the circumstances in a disaster
area (Actually, on some occasions, nutrient or organic loading is not always harmful
to the environment, but pathogens have to be removed in any case).
Our experience was useful in searching for an appropriate treatment for storm
water combined with untreated wastewater, which is discharged into open bodies of
water when the sewer overfl ows due to an overabundance of rainwater. A combination of coagulation-sedimentation and ultraviolet disinfection was tested and found
to be the most effective method for producing relatively safe water.
Polysulfuric ferrite, a waste byproduct from the iron and steel industry, was
selected as the coagulant. It was also used as an anti-odor agent for municipal wastewater. Polysulfuric ferrite is used for organic wastewater treatment in the food
industry, among others. The proposed method successfully removed suspended solids and turbidity from the infl uent, and achieved a good amount of bacterial and
viral removal when used together with ultraviolet light disinfection. This result was
presented at a wastewater works conference.
Our method was not applied in reality in Ishinomaki City because it requires
waste sludge management after the coagulation and sedimentation. The sludge
management system was restored almost at the same time as the other water
treatment facilities, and the wastewater treatment plants selected a biological
treatment. The method the task team developed will be used in the future or in
other recovery areas in the Tohoku region. The sampling campaign for water
quality in the coastal area is still contributing to future water quality management
plans from the viewpoint of microbial water safety. During the course of the
project, much support was given to us by senior professors, stakeholders, and
laboratory staff. Overall the author experienced a strong leadership applied under
such a tragic disaster by integration of multi-stakeholders and application of scientifi c Knowledge.
Open Access This article is distributed under the terms of the Creative Commons
Attribution Noncommercial License which permits any noncommercial use, distribution,
and reproduction in any medium, provided the original author(s) and source are credited.
T. Akiyama et al.