Estimation of Zn and Cu unit output loads from animal husbandry facilities

Abstract

Zinc (Zn) and copper (Cu) are toxic to aquatic organisms at very low concentrations that do not affect humans. We measured the daily output of Zn and Cu in wastewater from livestock farms to aquatic environments because waste from animal husbandry operations contains high levels of Zn and Cu. At most pig farms in Japan, a mixture of urine, some faeces, and service water is treated in onsite wastewater treatment facilities and discharged into a water body. Some dairy farms also have wastewater treatment facilities. We surveyed 21 pig farms and six dairy farms. The unit (i.e., per head) output load from piggery wastewater treatment facilities ranged from 0.13 to 17.8 mg/head/d for Zn and from 0.15 to 9.4 mg/head/d for Cu. Over 70% of pig farms had unit output loads of Zn and Cu below 6 and 2 mg/head/d, respectively. For dairy farms, the unit output load from wastewater treatment facilities was estimated at 1.8-3.6 mg/head/d for Zn and 0.6 mg/head/d for Cu. The unit output load for Zn from piggery wastewater treatment facilities was similar to that from treatment facilities for human waste. However, pig farms generally raise several thousand to tens of thousands of pigs; pig farms are therefore presumed to be a significant point source of Zn in rural areas.

Assessment of Potential Risk to Aquatic Organisms by Zinc Originating from Swine Farm Effluent in a Rural Area of Japan

“…We found that the concentration of Zn in the swine farm effluent at P5 exceeded both the ES (2.0 mg L -1 ) and the maximum effluent concentration from the WWTF (4.4 mg L -1 ; Abe et al 2012). We consider this high concentration to be undesirable but nevertheless probable based on the following supportive information.…”

“…The test scenario assumed the Zn concentration in effluent water to be controlled by the criteria for the maximum and average concentrations of Zn in effluent waters: 4400 and 470 μg-Zn L -1 , respectively ( Fig. 3; Abe et al 2012). We assumed that the effluent discharge remained the same.…”

“…We estimated the Zn and Cu concentrations in the effluent from swine farms at sites P5 and P6 in winter and summer and compared those estimates with the ranges of their concentrations in the effluent from a wastewater treatment facility (WWTF; Abe et al 2012) (Fig. 3).…”

“…Metallic zinc (Zn) can be an effective tracer for quantifying the contribution of swine farming to water pollution because Zn, as well as copper (Cu), is typically present at high concentrations in effluent from swine farms (Abe et al 2012, Suzuki et al 2010. These elements are added to commercial swine feeds to promote gain in body weight (Nicholson et al 1999, Tanaka 2005, but the swine absorb only 10-20% of the Zn and Cu and excrete the rest in their feces (Tanaka 2005).…”

“…In Japan, much of the fecal waste is removed from the barn for manure production, while the rest is diverted into wastewater alongside urine and maintenance water used to clean the swine enclosures. Consequently, the wastewater from a swine farm is highly contaminated with Zn and Cu; typical concentration ranges are 1.3-40 (average 11) mg L -1 for Zn and 0.44-21 (average 3.7) mg L -1 for Cu (Abe et al 2012).…”