Insolubilization of multi harmful waste(F,Cr（Ⅵ）)①

Arsenic is removed from groundwater without degrading the water quality unique to the area

Emergence of a problem

We were approached by a customer, whose business included the recycle and reuse of smoke dust and burned ash as a basecourse material from the volume reduction processing of industrial waste. This customer found that heavy metals such as fluorine and hexavalent chrome were present in the smoke dust and burned ash, and determined that an elution inhibition technique was required.

Diagnosis

The customer had already used an organic heavy metal treatment agent but needed to reduce per unit cost of the treatment agent.
Additionally, the customer wanted to reconsider the seemingly excessive measures being taken, considering that the concentration of heavy metals in the effluent was only slightly over the standard concentration.
Reducing the cost of the treatment agent was expected to revitalize the whole business because the customer could accept a larger amount and types of smoke dust and burned ash.

Validation

In this case, as the main purpose was reduction of costs, we held a discussion regarding the desired budget for the treatment agent and the process flow and processing equipment to replace the treatment agent that was currently in use.
As a result of the discussion, we realized that it was necessary to achieve a considerable reduction in cost. Furthermore, upon confirming the equipment to be used for processing, it was clear that the material had to be powdered and that it must be added by at least a prescribed amount in order to mix uniformly with the smoke dust and burned ash. It was difficult to meet the above conditions with the products being used at the time; therefore, we developed a new product.

Planning

Because the approach of the development plan was to ensure a low cost product, we collected information on fluorine and hexavalent chrome to conceive the simplest active chemical components and reaction mechanisms. Trial products were synthesized from various materials by a labor-intensive process and repeated trial and error; consequently, AC-1 was developed.
AC-1 was added to smoke dust and burned ash provided directly from the site, and the elution suppression effect was validated.
Thus, the concentration of eluted fluorine and hexavalent chrome decreased below the standard concentration while staying within the acceptable budget. This result was reported to the customer and a field test was conducted. In the field test, good results were obtained in an elution test after evaluating the possible influence on the equipment and the mixed state of the agent.

Solution to the problem

At this stage, the requirements of the customer were satisfied; however, the customer suggested that “while not absolutely necessary, it would be great if the strength was increased a little bit as the product was to be used as a basecourse material.” Regardless of whether or not it was imperative, we immediately investigated this matter as well, being aware that a real solution must fully meet the requirements of the client.
We improved the strength by customizing AC-1. After confirming that no problems were encountered and that the processing costs were within the budget, a new proposal was drafted, presented, and adopted.

Comments from the person in charge

At a minimum, we must meet the initial requirements, and AMEC can meet the customer’s requirement at any given time. We see increased requirements as proof that we are gaining trust.