# Enhancement of a Spent Irrigation Water Recycling Process: A Case Study in a Food Business
## 2 Methods
### Context  
The company selected for the case study is a food business located in central England. It grows beansprouts and other sprouted seeds and uses more than 6 million litres of recycled water weekly. Spent irrigation water is first filtered through a 20 \(\upmu\)m drum filter to remove suspended solids. The water is, then, treated with chlorine and citric acid to balance the pH. Chlorine dioxide is, then, used as part of the microbial disinfection process. However, these processes only allow the business to recycle in the region of 50-60% of the spent irrigation water daily, with the remainder being disposed of as waste to effluent. This disposal means that potable mains water must be introduced into the process to replenish the volume disposed of.  
The challenge facing the business is to recycle a significant amount of water, whilst remaining compliant with EU legislation regarding water quality. The European Sprouted Seed Association (2016) details that in order to comply with Commission Regulation (EU) No 210/2013 on the approval of establishments producing sprouts pursuant to Regulation (EC) No 852/2004, \"through all steps of the production process, water that comes into contact with seeds or sprouts should be water meeting the microbiological requirements of potable water listed in Council Directive 98/83/EC, Annex I, part A\" [26]. This is supported by Section 13 of EU Regulation 209/2013 as regards the microbiological criteria for sprouts [...] that details that \"food business operators producing sprouts should therefore comply with the food safety criteria for ready-to-eat food laid down in Union legislation\" [27]. Section 11 of the same regulation says that \"testing of spent irrigation water for pathogenic bacteria has been proposed as an effective indicator of the types of micro-organisms present in the sprouts\".  
The company manages this process and pathogen risk by treating the spent irrigation water with chlorine dioxide to reduce microbial levels within the water. Due to potential changes to EU legislation, the use of chlorine dioxide as a decontamination step is now under review.  
In 2015, the European Food Safety Authority was directed by the European Commission to conduct a review of chlorate levels. The review concluded that there were potential risks associated with chlorates in food products and made recommendations for future limits [28]. Following this study, the European Commission tabled a proposed amendment to Annex III to Regulation (EC) No 396/2005 of the European Parliament and the Council regarding maximum residue levels for chlorate in or on certain products [29]. The recommendations made were that the maximum residue limits (MRLs) for section 0251000, i.e., \"Lettuces and salad plants\", a sub section of 0250000 \"Leaf vegetables, herbs and edible flowers\", should be set at 0.15. Products that fall under the \"Lettuces and salad plant\" category and are also governed by the 0.15 limit are lamb's lettuces/corn salads, lettuces, escaroles/broad-leaved endives, cresses and other sprouts and shoots, land cresses, roman rocket/rucola, red mustard, baby leaf crops (including Brassica species), and others. Beansprouts and sprouted seeds are categorized under 0251040 \"Cresses and other sprouts and shoots\".  
Previous analysis undertaken in the company found that beansprout products on the open market have MRL chlorine levels well in excess of the proposed limits. The Agriculture and Horticulture Development Board claimed that chlorate exceedance is most likely to arise from chlorine dioxide or other chlorinated water used for crop irrigation [30]. Furthermore, although chlorine disinfection of waste process water is widespread, it recently came under criticism due to toxicity concerns [31]. This suggests that if the business is to remain compliant with amended legislation, an alternative water treatment process may be soon required.