Biological Treatment

Hoffland Environmental manufactures custom designed biological treatment systems to remove organic contamination from wastewater. In the case of sanitary waste, HEI manufactures a complete line of package treatment plants varying from 1000 gallons per day to 500,000 gallons per day. Units up to 50,000 gallons per day are shipped as factory assembled modular units. Units over 100,000 gallons per day are usually assembled on site. Tertiary filters are included when the discharge limitations are very stringent.

For industrial wastewater containing high levels of soluble organic products, it is usually more economical for the generator to pre-treat the wastewater, reducing the COD level to less than 500 and significantly reducing the city imposed surcharge. HEI customizes its system for each particular customer.

In one case to compensate for large surges of wastewater containing a significant level of organic contamination, the system included biotreatment in the equalization tank before secondary treatment. By treating the waste as it accumulated, adequate time was gained for the microbial culture to populate and consume the organic constituents. Secondary treatment then removed the suspended solids, filtered the water and adsorbed all remaining organic components as the water passed through a carbon adsorption vessel. All hydrocarbons were economical removed and load on the carbon was so low that carbon has not been replaced in over two years of service.

It is usually far more economical to remove organic contamination by active biological oxidation rather than carbon adsorption. In addition, most hydrocarbons that are highly water soluble are not readily adsorbed by carbon. These same compounds that are not adsorbed by carbon are easily decomposed by biological oxidation.

At a groundwater remediation facility, the collected water was initially processed through an oil water separator and a dissolved air flotation unit to remove all solids and insoluble organic material. Then the bio-oxidation unit removed the remaining soluble organic compounds. The excess biofloc was removed by a secondary clarifier, before filtration by a sand filter and further filtration by carbon adsorption. The prudent use of the bio-oxidation unit dramatically extended the life of the carbon adsorption media.

Hoffland Environmental custom designs its systems to include oil water separation and suspended solids removal before bio-oxidation if the added equipment is economically justified. HEI manufactures the entire system including not only the bio-oxidation unit but also oil water separator, clarifiers and solids separation and solids compaction equipment.


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