To prevent eutrophication of surface water, phosphate needs to be removed from sewage. Iron (Fe) dosing is commonly used to achieve this goal either as the main strategy or in support of biological removal. Vivianite (Fe(II) 3 (PO 4 ) 2 *8H 2 O) plays a crucial role in capturing the phosphate, and if enough iron is present in the sludge after anaerobic digestion, 70 to 90% of total phosphorus (P) can be bound in vivianite. Based on its paramagnetism and inspired by technologies used in the mining industry, a magnetic separation procedure has been developed. Two digested sludges from sewage treatment plants using Chemical Phosphorus Removal were processed with a lab-scale Jones magnetic separator with an emphasis on the characterization of the recovered vivianite and the P-rich caustic solution. The recovered fractions were analyzed with various analytical techniques (e.g., ICP-OES, TG-DSC-MS, XRD and Mössbauer spectroscopy). The magnetic separation showed a concentration factor for phosphorus and iron of 2-3. The separated fractions consist of 52% to 62% of vivianite, 20% of organic matter, less than 10% of quartz and a small quantity of siderite. More than 80% of the P in the recovered vivianite mixture can be released and thus recovered via an alkaline treatment while the resulting iron oxide has the potential to be reused. Moreover, the trace elements in the P-rich caustic solution meet the future legislation for recovered phosphorus salts and are comparable to the usual content in Phosphate rock. The efficiency of the magnetic separation and the advantages of its implementation in WWTP are also discussed in this paper.

No abstract

No abstract

Natural organic matter (NOM) can influence pharmaceutical adsorption onto granular activated carbon (GAC) by direct adsorption competition and pore blocking. However, in the literature there is limited information on which of these mechanisms is more important and how this is related to NOM and pharmaceutical properties. Adsorption batch experiments were carried out in ultrapure, waste- and surface water and fresh and NOM preloaded GAC was used. Twenty-one pharmaceuticals were selected with varying hydrophobicity and with neutral, negative or positive charge. The influence of NOM competition and pore blocking could not be separated. However, while reduction in surface area was similar for both preloaded GACs, up to 50% lower pharmaceutical removal was observed on wastewater preloaded GAC. This was attributed to higher hydrophobicity of wastewater NOM, indicating that NOM competition may influence pharmaceutical removal more than pore blocking. Preloaded GAC was negatively charged, which influenced removal of charged pharmaceuticals significantly. At a GAC dose of 6.7 mg/L, negatively charged pharmaceuticals were removed for 0-58%, while removal of positively charged pharmaceuticals was between 32-98%. Charge effects were more pronounced in ultrapure water, as it contained no ions to shield the surface charge. Solutes with higher log D could compete better with NOM, resulting in higher removal.

No abstract