Egg wash wastewater: Estrogenic risk or environmental asset?
Commercial production of eggs and egg products requires the washing of eggs to remove urinary / fecal material and broken egg residue. In the case of one Ohio farming facility, 1.6 million birds produce 1.4 million eggs per day, using ∼50 mL of wash water / egg or ∼ 70,000 L per day. The aqueous waste stream was evaluated for estrogenicity, to determine if potential for endocrine disruption would result from agricultural application of such wastewater. Samples collected the Fall (October) of 2010 included: water from two egg washers operating in series, inlet pipe to the treatment lagoon, a lagoon composite, and products used within the facility in the cleaning of equipment and treatment of the waste. In February 2011, the treatment lagoon was fitted with an extensive aeration system and subsequent sample sets were collected on three consecutive days in May and November. Samples were extracted by solid phase extraction and assayed for estrogenic activity using the in vitro E‐Screen assay. Raw untreated wastewater from the egg washers contained 17 ß‐estradiol equivalents (E2EqS) ranging from 9 to 18 ng/L, pipe grab samples entering into the treatment lagoon ranged from < 0.14 to 4.4 ng/L (variability related to time of emptying of egg wash tanks), while treatment lagoon water contained 0.3 to 4.0 ng/L E2Eq . Addition of an aeration system to the treatment lagoon eliminated surface “frothing,” reduced noxious odor emission, and E2Eqs were lower than the pre‐aeration concentrations (4 ng/L (n=1, no statistical comparison possible) versus 0.3 to 1.4 ng/L in 2011). Due to matrix effects, estrogens were not quantifiable by LC‐MS2 in even egg washwater extracts, at concentrations in which internal deuterated estrogen standards were quantifiable. Estrone and E2 parent ions were detected in egg washwater samples only, and confirmatory ion fragments were detected in only one of these samples. Estrogenicity of the wastewater from the treatment lagoon was already at the proposed aquatic no effect concentration for 17ß‐E2, and would be expected to decrease further as wastewater passes through two consecutive storage ponds prior to application on field crops for irrigation. The original project plan was to follow the wastewater as it was applied by aerial irrigation and concomitant surface runoff, but based on the consistent and extremely low concentration of estrogenic activity of the wastewater from the treatment lagoon, it was concluded that activity would be below limits of quantitation by E‐Screen in water used for irrigation from the storage ponds. Utilization of egg wash wastewater ‐ or gray water ‐ to irrigate crops, removes the cost and burden of wastewater treatment by the local wastewater plant, poses little to no potential threat of estrogenic endocrine disruption, and supports the conservation of water resources through the use of wastewater irrigation. Integr Environ Assess Manag © 2013 SETAC