61    LOW-RATE ANAEROBIC TREATMENT OF A POTATO
PROCESSING PLANT EFFLUENT
Robert C. Landine, Head Environmental Engineering Division
Stephen R. Pyke, Environmental Engineer
Graham J. Brown, Environmental Engineer
Albert A. Cocci, Senior Environmental Engineer
ADI International, Inc.
Fredericton, New Brunswick, Canada E3B 4Y2
INTRODUCTION
In 1985, ADI was commissioned to design and conduct a seven month anaerobic pilot plant
treatability study. The on-site pilot was to simulate a proposed full-scale, anaerobic process, and was
to be operated at loadings and hydraulic retention times (HRT) anticipated in full-scale operation.
The full-scale and pilot anaerobic technology chosen was the ADI-BVF. This is a low-rate digestion
process which has proven advantages in the treatment of potato processing wastewaters. Advantages
which made this technology the choice process included: ability to treat high concentration of SS,
effective and reliable wastewater treatment, ability to absorb shock loads, economical construction
and operation, digestion of waste solids from aerobic processes, energy production from biogas, and
simplicity of operation.
The objectives of this study were to evaluate the treatability of the potato processing wastewater
(including peel waste), as well as evaluate the performance of the technology for the purpose of
verifying full-scale design criteria. Wastewater treatment plant personnel carried out the day-to-day
operation of the plant. Supervision and sample analysis was provided by ADI.
PILOT STUDY
Apparatus
The pilot plant, illustrated schematically in Figure 1, consisted of: 1) an 840 litre (220 gallons) liquid
volume BVF pilot reactor, 0.61 metres (24 inch) diameter by 3.3 metres (10.8 feet) long complete with
heaters, thermostats, thermometers, insulation, manual mixers, influent and effluent headers, and
sludge recycle piping, 2) two 200 litre raw wastewater and feed storage drums, 3) variable-speed,
peristaltic pumps (raw wastewater, feed, and recycle) with timer controls, 4) variable-speed, feed
mixer, and 5) wet-tip biogas meter.
Operation
The reactor was seeded with 116 litres (31 gallons) of anaerobic sludge obtained from a municipal
treatment plant primary digester, 45 litres (12 gallons) of raw wastewater and 679 litres (179 gallons)
of tap water, and it was heated to 28°C (82°F). Following seeding, the reactor was nursed through a
startup phase (day 1 to 63) during which raw wastewater, peel waste, nutrients, and alkalinity were
added in either 10 or 20ro increments until full feed strength was attained. To promote reactor
maturity during startup, therapeutic anaerobic seed sludge dosages were added directly to the reactor
on day 30 (20 litres or 5 gallons), day 36 (20 litres or 5 gallons), and day 44 (30 litres or 8 gallons).
Operating temperature was increased to 35°C (95°F) on day 42.
Following startup, the study proceeded through a steady-state operation phase at 35°C (95°F) from
day 64 to 154, and at 28°C (82°F) from day 155 to 189. Operating temperature was reduced from 35 to
28°C (95 to 82°F) over a seven-day period (day 155 to 162) at a rate of approximately 1°C per day
(2°F per day). Following steady-state, two stress loading periods (day 190 to 194 and day 200 to 203)
were conducted at 28°C (82°F). The pilot then remained idle until completion of the study and
dismantling on day 213. Further reactor operation details are provided in Table I.
511