A large cereal manufacturing company had an ongoing problem meeting local metropolitan waste water discharge limits. It was found that suspended solids levels were frequently in breach of licence limits. At times other parameters also exceeded these limits.
Aquadynamic Consultancy Services profiled the waste water system for a period of three weeks. Autosamplers were installed at various points to collect samples from the three main ex-factory waste streams at hourly intervals. These samples were then tested for suspended solids, BOD, grease and petroleum hydrocarbons. In addition daily water usage was recorded. All results were tabulated and graphed.
(b) The Test Results
It was found that the suspended solids from one particular waste stream were frequently in excess of licence limits with regard to both the peak and composite loadings. However the other parameters were within limits most of the time.
(c) Bench Scale Trials:
Small scale laboratory trials were conducted to determine the best method of suspended solids reduction. Methods trialed included addition of various flocculants and mechanical settling methods.
Trial results conclusively showed that an inclined plate separator would be the most effective way to reduce suspended solids in the target waste stream under most conditions.
We recommended a suitably sized inclined plate separator be installed to treat the problem waste stream. In addition a DAF (dissolved air flotation) plant was proposed to ensure that this waste stream was compliant with licence limits at all times.
The company implemented the above recommendations, installing a waste water plant which incorporated both a plate separator and a DAF unit. Since this time the treatment plant has functioned well with final effluent meeting licence limits.
Ongoing Monitoring and Consultancy :
Since the plant upgrade Aquadynamic Consultancy Services has monitored the system regularly, making recommendations and adjustments to plant operation as required.