1 3 Mine Water Environ DOI 10.1007/s10230-016-0424-2 TECHNICAL ARTICLE Characterization and Toxicity Assessment of Wastewater from Rock Phosphate Processing in Tunisia Ali Mekki 1  · Asma Awali 1  · Fathi Aloui 1  · Slim Loukil 1  · Sami Sayadi 1   Received: 4 July 2016 / Accepted: 14 November 2016 © Springer-Verlag Berlin Heidelberg 2016 Burnett 1994). Gnandi and Tchangbedji (2006) observed that some diseases, such as dental luorosis in children, are strongly related to the luoride in the phosphate rock. Also, ine phosphate particles generated by mining have been found to negatively afect the human respiratory system (Pope and Burnett 2002). McDonnell et al. (2000) showed that they contribute to the incidence of cancer, while others have found that they can cause respiratory diseases, such as bronchitis and asthma (Herich and Holscher 2002). With over a century of experience in mining, upgrad- ing, and marketing Tunisian phosphates, the Company of Phosphates of Gafsa (CPG), is one of the world’s leading phosphate producers (Narasiah et al. 1988). Production exceeded 8 million metric tons (t) in 2010, making CPG the world’s ifth largest phosphate producer (Tijani and Fakhfakh 2011), though social unrest in Tunisia has sub- sequently afected production. The CPG works 10 surface mines in ive phosphate ields, all in the same Eocene geo- logical level, principally based around deposits in the Gafsa basin in southern Tunisia (Tijani and Fakhfakh 2011). The phosphate is ‘washed’ in several phases, including mechan- ical separation and treatment, to increase the P 2 O 5 content (Narasiah et al. 1988). This consumes 5 t of water per ton of phosphate. However, of these 5 t of water, 3.65 t were recycled, 0.15 t accompanies the phosphates product as moisture, and 1.2 t are lost (Narasiah et al. 1988). Thus, production of 8 million tons per year of market- able phosphate consumes approximately 10.5 million tons of waters (Tijani and Fakhfakh 2011). Moreover, the water that is being used by CPG is paleowater from Inill Conti- nental, and is not renewable (Tijani and Fakhfakh 2011). In this study, we characterized CPG’s wastewater from phos- phate ore processing (WWPP) and investigated its efects on the receiving environment, in particular the soil, in order to develop a suitable water treatment process. Abstract Phosphate ore processing wastewater (WWPP) from the Gafsa phosphate region of Tunisia was charac- terized. The WWPP had a very high turbidity, an almost neutral or slightly alkaline pH, and high salinity. The aver- age chemical and biochemical oxygen demands (COD and BOD) met wastewater discharge standards, but the COD/ BOD5 (4.34) signiicantly exceeded biodegradability val- ues. Total nitrogen, residual phosphorus, and some oth- ers chemical constituents exceeded wastewater discharge standards. Microbiological enumeration showed that the eluents were very low in microlora. Untreated WWPP and diluted (WWPP/4) inhibited bioluminescence of Vibrio fischeri by 76 and 45%, respectively. The WWPP had a phytotoxicity rate of 20–70%, respectively, for alfalfa and tomato seeds. Adding the eluent to soil for 60 days reduced the residual phytotoxicity of the WWPP-irrigated soil to about 15 and 34%, respectively, for tomato and alfalfa seeds. Keywords Waste water · Phosphate industry · Salinity · Toxicity · Soil Introduction The phosphate industry is the cause of many environmen- tal problems (Lipfert et al. 2000; Pope and Burnett 2002). Natural phosphates contain many metallic elements, some of which can negatively afect the environment (Jarvis and * Ali Mekki a_mekki_cbs@yahoo.fr 1 Laboratory of Bioprocesses, Center of Biotechnology of Sfax, AUF (PER-LBP), BP 1177, 3018 Sfax, Tunisia