What the Project Entailed
An Overview:
The Suntory winery north of Tokyo had a problem: expanded grape pressing operations would soon raise the BOD of the plant’s 0.53 MGD of wastewater from 1,500 ppm to 3,000 ppm, overloading the facility’s aeration lagoons.
Project Scope & Requirements
Treatment options were limited. Additional lagoons would take up precious space, generate twice as much sludge, and be just as susceptible to shock loads as the existing system. Anaerobic digesters were another possibility, but they would require close operator attention to function properly. Rotating biological contactors (RBCs) would be expensive both to install and maintain. A trickling filter would take up far too much space.
In view of the limitations of conventional equipment, Suntory engineers opted to do a pilot test of the latest in aerobic treatment technology: the continuously selfcleaning fixedfilm (CSCF) BioReactor developed by the Able Co. of Japan, packed with No.4 NUPAC® supplied by Lantec Products.
Why NUPAC was Used
Wastewater entering the top of the reactor is aerated and mixed by an airlift system. NUPAC® breaks the air stream into fine bubbles, resulting in oxygen transfer so efficiently that the system uses only about half the air of conventional fixed-film reactors. The packing has a specific surface area of 38 ft2/ft3, with uniform spacing of the polypropylene rods for easy dislodging of accumulated biofilm.
The packed section is rotated slowly over an airshearing device to control the thickness and age distribution of the attached biofilm, and prevent the development of anaerobic conditions. Although the microbes remain in a high growth phase, they form a fully developed food chain, in which larger organisms consume smaller ones. The net result is more BOD conversion to water and CO2, and less to bio-mass, so that sludge production is minimized.
Meeting the Requirements
A pilot reactor 3 ft in diameter and 9 ft tall was installed at the winery. After a 3-week startup period, the unit reduced average BOD levels from 2,370 ppm to 326 ppm even without clarification. When coagulant was added and suspended solids settled out, the BOD fell to 11.8 ppm. The unit destroyed 137 lb of BOD per day per 1,000 ft3 of reactor volume, compared with 40 lb/day/1,000 ft3 for a typical activated sludge process.
The acclimated biofilm was highly resistant to shock caused by abrupt changes in BOD loading. Longterm variations in loading could be compensated for by adjusting the frequency of air shearing.
Based on these results, Suntory is reviewing plans for a full-scale system of three reactors, each 25 ft in diameter and 20 ft high. These will reduce the loading on the existing system, destroying as much BOD as two 1,300,000 gallon aeration lagoons, in a fraction of the space.
The CSCF BioReactor recently won the annual prize for innovative environmental treatment technologies awarded by Japan’s Ministry of International Trade and Industry. It has a simple design which allows it to operate with minimal operator attention or maintenance.
