The facility involved in the test was a 14,600-head nursery/finisher in Olvia, MN. The unit had 24” pull plugs that were recharged with lagoon water. The storage system consisted of a 25 million-gallon, 6 acre primary lagoon and an 8 million-gallon secondary lagoon. Maximum depth in the primary reached 12 feet deep.

This facility was being monitored by the Minnesota Pollution Control Agency (MPCA) for hydrogen sulfide violations at the property lines. Between April and September, hydrogen sulfide readings were taken every 30 minutes, 24 hours per day. In addition, manure had built-up in the pull plug pits as well as the primary lagoon.

Pit Remedy was added to both the lagoons and the buildings in April 1998. Within 30 days the hydrogen sulfide emissions from the buildings were reduced by 60%. Hydrogen sulfide emissions from the primary lagoon continued to drop through the spring and early summer. Small-scale aeration began on July 8^th in the primary lagoon and by mid-August the facility was in compliance with the MPCA until the test ended September 11^th. A summary of this study follows below. The entire study is available on the web at (http://pasture.ecn.purdue.edu/~odor/).

The end results of treatment were lowered effluent readings of several key indicators of wastewater strength: biochemical oxygen demand, chemical oxygen demand, volatile fatty acids and suspended solids. These reduced values were directly correlated to reduced hydrogen sulfide emissions at facility property lines and significantly reduced odor levels.

ANALYSIS OF AMBIENT HYDROGEN SULFIDE CONCENTRATIONS
NEAR A HOG PRODUCTION FACILITY
by Albert J. Heber, Ph.D., P.E., Associate Professor
Agricultural and Biological Engineering Department
Purdue University
West Lafayette, IN 47907-1146
765-494-1214
Updated from Dr. Heber’s Final Report
February 28, 1999

INTRODUCTION

Hydrogen sulfide emissions in Minnesota are enforced by the Minnesota Pollution Control Agency (MPCA) according to their ambient air quality. The half-hour hydrogen sulfide concentration limits of 30 parts per billion (ppb) and 50 ppb are currently being imposed upon swine production facilities. The 50-ppb limit must not be exceeded over two times per year and the 30-ppb limit must not be exceeded more than twice during any five consecutive days. This standard must be met at the property boundary of the emitting facility. In response to any complaints about a farm’s odor, the MPCA sends an employee to screen the site for potential hydrogen sulfide problems at the property line using portable hydrogen sulfide meters such as the Jerome meter. The farm is notified if concentrations are near or above 30 ppb at the property line and the MPCA places a continuous 24-hour hydrogen sulfide monitor to produce an official hydrogen sulfide reading in 30 minute increments.

One such facility was monitored by the MPCA and was found to be “out of compliance” at their property line. The hog production facility started using a bacterial pit additive, Pit Remedy, in attempts to lower the emissions of hydrogen sulfide from their buildings and their lagoons. Two monitors placed and maintained by the MPCA continuously measured hydrogen sulfide concentrations in two directions (northwest & southeast) from the facility.

The objectives of this analysis were to:

Evaluate ambient hydrogen sulfide measurements taken by the Minnesota Pollution Control Association, and
Correlate hydrogen sulfide measurements with slurry characteristics, wind speed and direction, and time of day.
Evaluate overall effectiveness of the product (Pit Remedy) in this environment.

Description of Swine Facility

The swine finishing facility consisted of two recirculating cells, eight nurseries and eight finishing buildings with 24-inch deep pits that were flushed every four weeks. The total number of pigs at the site was 14,600 and the average weight of the pigs was around 135 lbs. The volatile solids production rate into the first cell was calculated as 8,712 lbs. per day or 4.35 lbs. of VS per 1,000 ft³ per day. The first cell volume was 25,000,000 gallons and the second stage lagoon volume was 7,500,000 gallons. The areas of the first and second cells were 261,124 and 139,084 ft² (6.0 and 3.2 acres) respectively. The dimensions of the first cell were 402x687 ft. The dimensions of the second cell were 232x652 ft. Each cell was 14 ft deep including a 2-ft freeboard.

Product Application Schedule

The dosage rate for the product was 0.5 gallons/month per 1,000 nursery pigs and 1.0 gallons/month per 1,000 finishing pigs.

The product was added to the barn pits at the rate of 12 gallons per month. Initially, for each gallon of bacteria, one gallon of catalyst was also added. Specifically, the mixed product was added at the rate of two gallons per finishing room and one gallon per nursery in the pull plug pits. The product flows with the manure into the first-stage lagoon by gravity when the individual pits filled (every four weeks). Eighty gallons were added directly to the first stage lagoon on March 26 followed by 40 gallons on April 15, May 6, June 5 and July 9 for a total of 240 gallons. Thus, a total of 336 gallons of product were added.

RESULTS

Slurry Characteristics

The analysis was taken from 14 slurry samples. The compounds usually associated with odor emissions (volatile fatty acids, sulfides, BOD) decreased significantly. The following is a summary of the results for each compound:

Volatile fatty acids decreased gradually from over 1,000 mg/L in May to 30 mg/L on Aug 26.
The BOD level in the lagoon decreased from between 3,000 and 6,000 mg/L in April, May and June to around 450 mg/L at the beginning of September.
The analysis of sulfides showed a steady decrease in concentration from 1.2 mg/L in April to around 0.4 mg/L in September.
The COD decreased from over 2,000 to under 50 mg/L by early September.
The total suspended solids increased from about 3,000 mg/L to over 18,000 mg/L. After aeration began on July 8, suspended solids decreased below 50 mg/L in early August.

Ambient Hydrogen Sulfide Concentrations

The northwest sensor (closest to the first stage lagoon) recorded 7,412 readings of hydrogen sulfide concentrations between April 6 and September 8. The average concentration of these readings was 5.3 ppb and the standard deviation was 10.4 ppb. The southeast sensor (closest to the building) recorded 3,593 readings of hydrogen sulfide concentrations between April 23 and July 8. The average concentration of these readings was 2.3 ppb and the standard deviation was 5.2 ppb.

Effect of Treatment

Average concentrations of hydrogen sulfide were calculated for successive 10-day intervals throughout the trial. At the SE sensor, the mean hydrogen sulfide concentrations steadily decreased from 13.9 ppb in mid-May to 5.6 ppb in late June. The product was added to the building pits on May 6. The 60% decrease in the reading at the southeast sensor apparently resulted from lower hydrogen sulfide emissions from the buildings as a result of the additives in the pit contents.

On July 7 an aeration system was installed in the settling cell near the inlet pipe. It operated until September 11. A 6-hp compressor and three air diffusers were located near the lagoon inlet pipes. The aeration system was installed to accelerate the effectiveness of the product in the first stage lagoon.

Hydrogen sulfide concentrations were reduced at the NW sensor by over 50% within one month after aeration started. After three weeks of aeration the percentage of the time that 30ppb was exceeded dropped to about 10%. During the final three weeks of the study, the exceedances dropped to 2.3 and 0% for days 135-144 and 145 to 154. These were the lowest levels since the trial began. Apparently, aeration and mixing were needed to speed up and enhance the effectiveness of the product in the first stage lagoon.

CONCLUSIONS