Development of Technology to Reduce Residual Ammonia Nitrogen in Treated Wastewater
1. Introduction
The main sources of ammonia nitrogen (NH4-N) in sewage are night soil, household wastewater and industrial wastewater. With some wastewater treatment plants, residual NH4-N is present in the treated wastewater, and the concentration exceeds 2 mg N/L at approximately 40% of small-scale treatment plants. Ammonia is known to affect aquatic organisms. When a lower target value is set for the NH4-N concentration of treated wastewater, many treatment plants may have to take measures to reduce the NH4-N concentration.
Therefore, the authors developed technology that can be added to existing treatment plants to reduce NH4-N, specifically at small-scale plants that employ treatment methods that make them difficult to take NH4-N reduction measures.
2. Overview of the developed technology
A compact treatment unit was developed by using microbial carriers that can accumulate a high concentration of microorganisms (nitrifying bacteria) for NH4-N treatment. It can be installed by adding only 10% of the space occupied by the existing treatment facility. Figure 1 shows an overview of the unit.
Fig. 1 Overview of the NH4-N reduction technology using microbial carriers
The technology could also achieve energy saving by reducing the redundant air-blowing supply, using an NH4-N sensor that optimizes the oxygen supply based on the NH4-N concentration, and adopting mechanical mixing of carriers instead of aeration. Figure 2 shows how both energy saving and NH4-N reduction are achieved simultaneously.
Genetic analysis has also confirmed that this operation method enables treatment of NH4-N by retaining a large amount of nitrifying bacteria in carriers. Figure 3 shows the results of confirmation of the nitrifying bacteria retaining status.
energy-saving air volume control and NH4-N reduction by using an NH4-N sensor |
retaining status in carriers through genetic analysis |
3. Use of the results
The results have been presented in a research paper, and it is expected that the technology will be utilized extensively as an NH4-N reduction measure at wastewater treatment plants in the future.
(Contact : Water Quality Research Team)
Introduction to Research Results: Support for winter traffic accident risk management
Fig.1 Application of spatial statistics
and traffic engineering to the
development of a traffic accident
risk analysis and evaluation method
Fig.2 Information on skidding accident
risks to urge drivers to take
precautions (Joint research with
the Hokkaido Police)
Fig.3 Development of a mobile
tool to assist with an
on-site traffic safety diagnosis
Although fatalities from road traffic accidents across Japan, including cold, snowy regions, have been on a downward trend, the decreasing rate has slowed recently. Accordingly, it is necessary to further reduce the number of traffic accidents.
Against this background, and by applying big data both in size and nature, we have established a method to enable the analysis and evaluation of potential traffic accident hot spots and the likelihood of traffic accidents (traffic accident risks), as well as a method to improve preparedness for traffic accident risks (traffic accident risk management). A tool to support traffic accident risk management has also been developed. Some of these research results are introduced here.
Firstly, correlation analysis in spatial statistics and traffic state estimation in traffic engineering were applied to big data on traffic accidents, the weather, traffic flow, road structures and other conditions, and a method of analyzing and evaluating areas where locations with a high traffic accident risk are concentrated was thus developed.
Figure 1 shows an example of applying this method to the Sapporo urban area. In the figure, areas where locations with a high risk of traffic accidents resulting in property damage are concentrated are identified, and traffic volume and vehicle speed at which property damage accidents are likely to occur in these areas are displayed. This information helps to select locations where traffic accident countermeasures are needed.
Secondly, we have provided information on the level of skidding accident risk obtained through joint research with the Hokkaido Police as precautions against skidding accident risks on winter roads.Figure 2 is an example of a traffic information board installed at Nakayama Pass on National Highway 230. On the information board, the level of skidding accident risk is displayed by the Hokkaido Police to urge drivers to take precautions. On days when the level of skidding accident risk is expected to become “Maximum” or “High” based on the snowfall, temperature and other conditions, the skidding accident risk level is displayed.
In terms of traffic safety diagnosis, which is one of the traffic accident risk management methods, we have also developed a mobile tool to assist on-site diagnosis of traffic safety. Traffic safety diagnosis is a system of providing effective technical advice on traffic accident countermeasures based on a site survey of locations with a high accident risk conducted by diagnostic teams consisting of National Highway Office technical staff and other staff members in response to requests from municipal road administrators or other authorities. This system is utilized by road administrators and other authorities throughout the nation because it is difficult to devise effective measures against traffic accidents due to the complexity of the causes of traffic accidents. The use of a mobile tool, as shown in Figure 3, on-site where a traffic safety diagnosis is made enables the search of traffic accident incidents filtered by meteorological, traffic and other conditions, the automatic creation of diagnostic reports, and the confirmation of the points to be observed and measures to be discussed.
We will continuously provide support to realize more effective and efficient winter road traffic accident risk management using these research results.
(Contact : Traffic Engineering Research Team, CERI)
Safe Snow Removal Operation Technologies in Snowstorms
Fig. 1 Snowplow
Fig. 2 Magnetic marker
guidance system
Fig. 3 Millimeter-wave radar system
Fig. 4 Snowplow leading system
In recent years, both the frequency and duration of national highway closures due to snowstorms or other winter weather hazards have been increasing in Hokkaido. To lift national highway closures, snow needs to be cleared with snowplows (Fig. 1). However, snowstorms may cause extremely limited visibility, so-called whiteout conditions. During a whiteout, snowplows are at risk of running off road or colliding with vehicles or pedestrians .Ambulances and other emergency vehicles have to use roads even if they are closed to get to their destinations. In this case, a snowplow sometimes leads an emergency vehicle. However, it is difficult for the driver of the emergency vehicle to see the snowplow ahead during a whiteout. Therefore, we have developed a systems and other solutions to enable safe snow removal operations in snowstorms.
Development of support systems
Technically it is possible for a vehicle to continue travelling on a roadway without swerving, during a whiteout, as long as it receives a signals from Michibiki, the Quasi-Zenith Satellite System. However, snowplows have to remove snow even in mountainous areas where receipt of signals from satellites is poor. Accordingly, we have developed a guidance system that uses magnetic markers (Fig. 2). With this system, vehicles equipped with magnetic sensors are guided by magnetic markers imbedded in the pavement, preventing the vehicles from swerving off the road. In An experiments, we comfirmed that snow removal can be performed by a snowplow guided by magnetic markers.
We have developed a millimeter-wave radar system (Fig. 3) that is capable of detecting vehicles and people even during a snowstorm. From experimental results, we confirmed that millimeter-wave radars can detect obstacles more than 100 meters ahead during a snowstorm. On the other hand, since snowplows travel at a slow speed, they are often passed by other ordinary vehicles. For this reason, snowplow operators must constantly pay attention to vehicles passing from behind. Therefore, we have also developed a millimeter-wave radar system designed for rear detection.
We developed a system (Fig. 4) that enables a snowplow to safely lead an ambulance or other emergency vehicles. A system can transmit real-time information including distance from the leading snowplow, braking, etc., a tablet in the emergency vehicle following behind the snowplow.
Protecting our living with technology
Snowplows must be able to remove snow even under severe snowstorm conditions. We will continuously be involved in the research and development of systems that enable safe snow removal, even under extreme weather conditions.
(Contact : Machinery Technology Research Team, CERI)