Endocrine disrupting compounds such as estrogenic steroid hormones (ESHs) are problematic when present in waterways in terms of both the health of the ecosystem and downstream water treatment. Dairy farms are some of the largest contributors to ESHs in the environment. This study focused on a farm located in the Waikato region, New Zealand, which housed 550, primarily grass-fed dairy cows. The farm included a rotary milking shed, feed pad, sump, covered anaerobic pond and storage pond, with effluent and sludge being applied to land. In this study concentrations of the conjugated and unconjugated ESHs, 17α-estradiol (17α-E2), 17β-estradiol (17β-E2) and estrone (E1), in both dissolved and solid phases of dairy shed effluent, and covered anaerobic pond sludge and effluent, were measured from grab samples over a period of nine months. These were used to investigate seasonal variation and performance of the covered anaerobic pond in removing the ESHs and their conversion from one form into another. Previously published methods of ESH analysis were validated and adapted for ESH analysis in dissolved and solid phases, and a new enzymatic method for conjugate ESH analysis was tested and used. In addition, the effect of dosing the effluent with biochar was examined on ESH removal. A covered anaerobic pond model was developed to examine the efficacy of a dairy farm-based covered anaerobic pond treatment system to settle, transform, absorb and remove ESHs. The model was calibrated utilising ESH measurements and used to examine the effect of biochar addition and operational parameters on ESH removal. Overall ESH concentrations in the covered anaerobic pond influent, sludge and effluent were 4,171 ng/L, 93,601 ng/L and 4,346 ng/L respectively. ESH concentrations peaked in dairy shed effluent during April and July, which correlated with the late pregnancy and calving periods on the farm. The mean organic carbon normalised adsorption coefficient (Koc) for ESHs in the samples from the pond treatment system ranged between 3.06 mL/g to 3.78 mL/g, comparable with published values in soil and wastewater sludge. Up to 99% of the total mass of ESHs in the sludge and between 70-80 % in influent and effluent were retained in the solids phase. The predominant ESH in the influent samples was 17α-E2 (2,869 ng/L), but E1 predominated in the sludge (85,414 ng/L) and in the effluent (3,140 ng/L). The dissolved and solid phases of dairy shed effluent contained the highest relative proportions of conjugated ESHs with means of 25.1 % and 3.38 % respectively and corresponding mean concentrations of 113 ng/L and 137 ng/L. In contrast, sludge and effluent samples (dissolved and solid phases) from the covered anaerobic pond contained smaller relative proportions of conjugated ESHs, 0.90 % and 1.21 %, and 7.17 % and 0.43 % respectively and corresponding mean concentrations of 6.65 ng/L and 967 ng/L, and 52.5 ng/L and 19.7 ng/L respectively. These results demonstrate the importance of considering the solid fraction within effluent treatment systems when analysing ESHs, otherwise estrogenic load can be greatly underestimated. The conjugated ESHs were present in both the dissolved and solid phases of all samples collected, indicating that conjugated ESHs are persistent and can pass through anaerobic treatment systems contributing to estrogenic load once applied to pasture, and potentially leach into groundwater or migrate to nearby surface waters. Overall anaerobic treatment of dairy waste decreased the contribution of 17α-E2 and 17-E2 while increasing that of E1, however, 17-E2 was the main contributor to total estrogenicity. The calibration of the model developed provided a good fit with experimental data with an R2 of 0.98-0.99. Addition of biochar into dairy shed effluent and the model covered anaerobic pond system resulted in an 89 % reduction of free ESHs but had a minimal impact on conjugated ESH. Addition of biochar increased the solid phase ESH concentration by 19 % settling out into the sludge and reducing overall estrogenic load in the effluent. Operational factors such as higher influent flow rates and sludge accumulation negatively impacted the covered anaerobic pond ESH removal performance. Sludge accumulation and short-circuiting caused by infrequent removal and shallow depth of the covered anaerobic pond system resulted in mixing of fresh influent with the upper layer of pond sludge, leading to decreased removal efficiency. To enhance the covered anaerobic pond system's performance, increasing the retention time and reducing sludge carry over by increasing pond volume and depth, resulted in ESH removal increasing to 67.9 % (no biochar) and 73.0 % (with biochar), and estrogenicity reduction improving to 70.4 % (no biochar) and 73.5 % (with biochar).