Purifying the Land of Kawasaki - A Story of Urban Renewal and Soil Purification (2007)

Purifying the Land of Kawasaki - A Story of Urban Renewal and Soil Purification (2007)

In the 2000s, soil contamination, a negative legacy of Japan's period of rapid economic growth, emerged as a bottleneck in redevelopment projects. 2003 saw the enforcement of the Soil Contamination Countermeasures Law, which made it mandatory to identify, report, and take measures to remediate contamination, and the market demand for rapid and reliable remediation increased dramatically. In response to this trend, Shimizu Corporation obtained a permit in Kawasaki City in 2005 and constructed a purification facility with a treatment capacity of 960 tons per day. The facility is capable of both on-site and off-site treatment, and has the flexibility to handle both large-scale projects and scattered contamination in urban areas.

The strength of the facility lies in its modular design, which allows the process to be reconfigured according to the contamination and site conditions. For heavy metals (lead, cadmium, arsenic, hexavalent chromium, etc.), soil washing (wet scrubbing, particle size classification, friction washing) is used to concentrate the soil into fine particles, and solid-liquid separation is performed with chelating agents and pH control. Residues are solidified and stabilized with cementitious or pozzolanic materials to reduce leaching. For oil contamination and polycyclic aromatics, low-temperature thermal desorption (150-350°C) promotes volatilization and decomposition, and the desorbed gas is detoxified by catalytic oxidation or activated carbon.

For volatile chlorinated organic compounds (TCE, PCE, etc.), thermal desorption and activated carbon adsorption are selected off-site, while soil gas suction (SVE) and air sparging are selected on-site. For straddling groundwater aquifers, pump-and-treat suction, aeration, and activated carbon treatment, or permeable reaction walls (PRBs) with zero-valent iron to reduce and decompose chlorides. For non-volatile persistent organic matter, chemical oxidation (ISCO) such as persulfate, permanganate, or the Fenton reaction should be applied, using either in-situ injection or drilling mixing methods depending on the permeability of the site.

The by-processing around the process is also thorough. Cleaning wastewater is coagulation sedimentation and filtration, polishing with ion exchange or activated carbon if necessary, and discharged within standards. Dewatering is carried out by belt presses and filter presses to lower the water content and reduce the amount of waste discharged. Dust and odor countermeasures include mist spraying in loading yards, negative pressure tents, and tire washing and sheet curing for vehicles as standard. Logistics will ensure traceability through manifest management, and risk communication will be thoroughly implemented by holding explanatory meetings for residents and disclosing the results of monitoring.

The key to construction management is both speed and quality. Preliminary detailed surveys are conducted using boring, cone penetration (CPT), and membrane interface probes (MIP) to determine vertical and horizontal distribution and optimize excavation boundaries. In the field, PID and GC-MS rapid measurements are used to modify the process in real time. Quality assurance is standardized to include sampling frequency, elution and content standards, and backfill material compliance, with transparency ensured through third-party verification. In terms of operation, parallelization of lines will increase peak throughput, and preventive maintenance (monitoring of vibration, temperature, and oil degradation) will minimize outages.

Kawasaki is a key location in the Keihin Industrial Zone and has great potential for reclamation of former factory sites and landfill sites, and its 960 tons per day class processing capacity and diverse technology portfolio have encouraged rapid land conversion to distribution centers, residential, and commercial. This initiative was not only an environmental measure, but also an implementation model for joining environmental business and urban renewal, and was a symbolic step in materializing the "brownfield to greenfield" concept of the 2000s.