Company ProfileCase Study: Dairy Farm—Slurry Lagoon, Little Malvern Farm, Welland, Malvern, UK
The Problem
All slurry, yard and milking area washings from this dairy farm were discharged to a slurry tower via a fiber screen. The fiber was stored and composted for land application while the liquor was transferred to an anaerobic lagoon, with a total capacity of 9,000,000 liters. Slurry was irrigated by tractor from the lagoon onto the outlying fields during spring and summer.
Complaints of foul odors were frequently received from neighboring houses when spreading occurred, depending on the prevailing wind. Negative publicity had reached the level of involving Central TV News and the local Environmental Health Officer.
In addition to solving an environmental issue, the farm wished to prevent ammonia evaporation from the lagoon in order to conserve fertilizer nitrogen value and reduce BOD. This would insure there would be no pollution of nearby groundwater and streams.
The EversTech Solution
With the lagoon level at 3,000,000 liters, EversTech began a bio-augmentation program which was scheduled to run for four weeks. During the first week, an inoculation dose of bio-cultures was added and the lagoon stirred daily by utilizing the lagoon feed pump.
For weeks two to four of the trial period, the dosage was reduced and added weekly, while continuing the lagoon mixing.
Successful Results
After the first week, there was already a noticeable change in the appearance of the lagoon. Fat deposits that had dominated corners of the lagoon surface had disappeared. The color was changing from green to brown.
During the second and third weeks, the color change to brown was even more significant and all traces of grease had disappeared. Areas of surface disturbance were occurring where the cultures had loosened deposits and sediment from the floor of the lagoon, and the foul smell was greatly reduced.
At the end of the fourth week, the intention was to spread the treated lagoon contents onto the fields. Unfortunately, the weather had deteriorated to such an extent that the tractor could not get onto the field without causing damage. The lagoon was therefore left until this improved.
Eventually, some six months later, the lagoon volume had increased to capacity (9,000,000 litres), with no further bio-culture addition. During the week when spreading finally did occur, there were no complaints of smell, even where the fields were directly adjacent to housing. The irrigation contractors also commented on the considerable difference in the slurry. They found it was easier to pump and no smell could be detected on the tractor or at the lagoon.
The effects of the bio-cultures on nitrogen availability could not be measured as the treated contents had been diluted too greatly.