Mine water ammonia and nitrate treatment process development

An Alaskan mine under development that was operating under a very strict operating permit encountered increasing ammonia (NH4-N) and nitrate (NO3-N) mine water discharge levels from the ammonium nitrate blasting agents used. Due to the limited land area available for installation of a biological plant sufficiently large to treat at least 1200 gallon/minute flowrates, Hancock was contracted to investigate and develop an innovative flowsheet that would provide a practical alternative to biological ammonia and nitrate degradation. The flowsheet developed that was bench tested with some cursory larger scale pilot tests included sequential and effective ammonia and nitrate ion exchange removal where the species were concentrated in strip solutions. These strip solutions were air stripped and a small bioreactor using brine tolerant bacteria. This was a innovative technically effective, relatively low capital cost and had good operating cost efficiencies alternative that met the project constraints provided by the client.

Mine water treatment plant startup and operator training

After an ~4 year shutdown, resumed mine activities required restart of the water treatment plant. The client hired Bill Hancock to support operational restart. Much of the previous operating experience had been lost during the intervening years. The assignment entailed working with the operators to check the mechanical soundness of the system, define initial operating conditions, trained the operators and conducted initial system optimization to ensure discharge permit limits were achieved.

Flocculation process control strategy for highly radioactive slurry

A DOE Hanford Site contractor responsible for transferring highly radioactive waste from leaking storage tanks to new bunkers that required a thickening and clarification step. The client required flocculation process expertise and hired Hancock to support their efforts. Due to the high radioactivity levels, the entire transfer process had to be accomplished in a 100% closed system that prevented observation. This required the client and consultant to develop highly effective thickening and clarification procedures that would be effective with all transfers to be made. The assignment entailed verifying flocculation process effectiveness, flowsheet review with improvement recommendations, providing training and developing a transfer procedure using simulant slurries as the actual materials were too radioactive to handle.

Water plant technical assessment

A mining company retained Bill Hancock to conduct a Colorado water treatment plant process technical assessment and plant capabilities audit in preparation for test mining and exploration work. The plant used a dissolved air flotation (DAF) process for clarification of predominant gypsum from the lime precipitation process followed by mixed bed filtration, thickening and belt filtration to consolidate the solids for haulage to waste disposal. Plant capability had to be assured because this mine was under intense environmental and local population scrutiny. An expert report was provided by the Consultant regarding the plant review along with recommendations for improving process performance.

Resolving drilling mud fluid negative impact on WTP clarification performance

Under new permit environmental limits, a USA mine installed a water treatment plant to treat a blend of mine water discharge and excess process mill water. The plant was misdesigned for the application and the client retained the Consultant to support resolution of the process shortcomings. Even after the flowsheet was optimized and the equipment upgraded, extended process excursions continued. In coordination with the client, further lab testing and assessments demonstrated that the diamond drilling synthetic drill mud combination was causing TSS hydrophobicity and particulate dispersion that was difficult to flocculate and clarify in the water treatment plant. The Consultant worked with drilling mud suppliers to assist in defining an improved mud formulation that would be easier to treat. Then a mud precipitation treatment program for drilling mud discharged to the mine water system was developed which the mine implemented. This combination greatly improved the water treatment process, which made it much more consistent and discharge limits manageable to consistently meet the discharge limits.