Reuse of pretreated cheese whey wastewater for industrial tomato production (Lycopersicon esculentum Mill.)

Due to the high organic load, suspended solids presence, fats content, salinity, etc., cheese whey wastewater (CWW) disposal/management represents a complex issue from an environmental and engineering point of view. In this work, an alternative wastewater management option is suggested. The process includes the CWW pretreatment by means of a basic precipitation stage followed by neutralization of the supernatant. This pre-stage is capable of reducing the organic, suspended solids and fats content to different levels. In a second step, the pretreated CWW has been used in the irrigation of tomato crops (cv. Roma and cv. Rio Grande). Different salinity levels corresponding to 1.75, 2.22, 3.22, 5.02 and 10.02dSm−1 have been tested. Taking into account the obtained results in control runs (fresh water), the salinity level of the pretreated CWW had no significant effect on the flower clusters number per plant, tomatoes number per plant, tomatoes number per cluster, longitudinal and transversal calipers and epidermis firmness of the fruits. Moreover, an increment of soluble solid content in fruits (16% for cv. Roma and 27% for cv. Rio Grande) was observed in saline treatments. Among the drawbacks experienced after irrigation with high salinity level were some physiological disorders such as blossom-end rot. In this line, epidermis firmness and caliper reductions were observed compared to marketable fruit although cv. Rio Grande was less sensible to the aforementioned disorder. The effects of irrigation with pretreated CWW on the soil properties were also investigated. As expected, soil conductivity linearly increased with the pretreated CWW salinity level. Additionally, soil contents in phosphorus, nitrogen and organic matter were increased after the pretreated CWW irrigation. Under controlled saline conditions, the tomato plants irrigation can be a solution for by-products management from cheese industry with the fruits characteristics improvement and the wastewater inadequate discharge reduction.