DEVELOPMENT OF PROCESS CONTROL EQUATIONS TO SUPPORT DETOXIFICATION OF COPPER USING NATURAL HUMATE AMENDMENTS

Looney, B. ; Millings, M. ; Halverson, N. ; Nichols, R.

关键词: WASTE WATER;    WATER TREATMENT;    COPPER;    DETOXIFICATION;    HUMIC ACIDS;    ADDITIVES;    PROCESS CONTROL;    COMPUTERIZED CONTROL SYSTEMS;    EQUATIONS;   

DOI  :  10.2172/960213
RP-ID  :  SRNL-STI-2009-00353
PID  :  OSTI ID: 960213
Others  :  TRN: US200923%%339

美国|英语

来源: SciTech Connect

【 摘 要 】

Recent scientific research and changes in regulatory policies have led to reductions in the allowable discharges of several contaminant metals, including copper, into surface water. Low target concentrations and variable outfall conditions challenge the efficacy of traditional treatment technologies such as ion exchange. In reviewing various treatment options, scientists and engineers at the Savannah River Site (SRS) developed a treatment strategy focusing on toxicity reduction (rather than the removal of the copper) and demonstrated that the method is viable and promising for mitigating copper toxicity. The resulting outfall chemistry protects the ecosystem in the receiving stream in a manner that is equal to, or better than, technologies that remove copper to the emerging regulatory levels. Further, the proposed toxicity reduction strategy results in collateral beneficial changes in outfall water chemistry such that the outfall more closely matches the chemistry of natural streams for key parameters such as the dissolved organic carbon (DOC). The detoxification process is based on the EPA BLM. Specifically, modeling indicates that copper toxicity can be mitigated by modest additions of natural organic carbon and that the amount of amendment needed can be determined based on pH and stream flow. The organic carbon amendments proposed for the treatment/detoxification process are extracts of natural materials that are produced for use in organic agriculture. These extracts are known by several common names such as potassium humate, soluble humic acid, and a variety of brand trademarks. When used to reduce ecosystem toxicity in surface water, these amendments bind copper and compete with the biological receptor sites, resulting in a reduction of impacts to key food chain organisms such as the Daphnia ('water flea'). Design and implementation of the process is straightforward. The core equipment consists of storage tank(s), pH sensor(s), outfall flow monitor(s), variable speed pump(s), and a programmable logic controller (PLC). The PLC collects information on pH and outfall flow, and modulates the pump flow rate to meter the correct amount of amendment into the outfall. A mathematical relationship, or control equation, is programmed into the PLC and serves as the basis of the operation. A summary of the development of, and key documentation for, the process control equation is provided.