Nitrate leaching under a land treatment system for dairy factory effluent

Abstract

The expansion of the dairy industry and the merger of processing companies (LIC, 1997; 1998) has implications for waste management. Dairy companies are building factories with increased peak capacities. In 1970, 200 sites processed just over S,000 million litres of milk, whilst in 1993, 30 sites were processing about 8,600 million litres (Barnett et al., 1994). As a result, effluents are produced in greater volumes at each site and may have highly variable characteristics depending on the product lines being processed. Disposing of large volumes of waste with variable characteristics requires a treatment system which is flexible and economic. In many cases, land application of wastes has been identified as having these benefits (Cameron et al., 1997). Incorrectly designed systems may have problems (leaching and ponding leading to surface runoff) which manifest themselves as environmental effects (elevated nitrate levels in groundwater and eutrophication respectively). Although the general mechanisms of nitrogen cycling are understood, the impact of dairy factory effluent (DFE) on these processes is not understood and has not been quantified. The objective of this research was to identify the effects of land treatment of DFE on nitrate leaching to groundwater.