Liat Birnhack

A new algorithm for design, operation and cost assessment of struvite (MgNH4PO4) precipitation processes

Deliberate struvite (MgNH4PO4) precipitation from wastewater streams has been the topic of extensive research in the last two decades and is expected to gather worldwide momentum in the near future as a P-reuse technique. A wide range of operational alternatives has been reported for struvite precipitation, including the application of various Mg(II) sources, two pH elevation techniques and several Mg:P ratios and pH values. The choice of each operational parameter within the struvite precipitation process affects process efficiency, the overall cost and also the choice of other operational parameters. Thus, a comprehensive simulation program that takes all these parameters into account is essential for process design. This paper introduces a systematic decision-supporting tool which accepts a wide range of possible operational parameters, including unconventional Mg(II) sources (i.e. seawater and seawater nanofiltration brines). The study is supplied with a free-of-charge computerized tool (http://tx.technion.ac.il/~agrengn/agr/Struvite_Program.zip) which links two computer platforms (Python and PHREEQC) for executing thermodynamic calculations according to predefined kinetic considerations. The model can be (inter alia) used for optimizing the struvite-fluidized bed reactor process operation with respect to P removal efficiency, struvite purity and economic feasibility of the chosen alternative. The paper describes the algorithm and its underlying assumptions, and shows results (i.e. effluent water quality, cost breakdown and P removal efficiency) of several case studies consisting of typical wastewaters treated at various operational conditions.

Accurate approach for determining fresh-water carbonate (H2CO3⁎) alkalinity, using a single H3PO4 titration point

A new, simple and accurate method is introduced for determining H(2)CO(3)(*) alkalinity in fresh waters dominated by the carbonate weak-acid system. The method relies on a single H(3)PO(4) dosage and two pH readings (acidic pH value target: pH~4.0). The computation algorithm is based on the concept that the overall alkalinity mass of a solution does not change upon the addition of a non-proton-accepting species. The accuracy of the new method was assessed batch-wise with both synthetic and actual tap waters and the results were compared to those obtained from two widely used alkalinity analysis methods (titration to pH~4.5 and the Gran titration method). The experimental results, which were deliberately obtained with simple laboratory equipment (glass buret, general-purpose pH electrode, magnetic stirrer) proved the method to be as accurate as the conventional methods at a wide range of alkalinity values (20-400 mg L(-1) as CaCO(3)). Analysis of the relative error attained in the proposed method as a function of the target (acidic) pH showed that at the range 4.0

Post-Treatment of Desalinated Water—Chemistry, Design, Engineering, and Implementation

Abstract The quality with which water is released from desalination plants increases continuously. However, prior to the post-treatment step, desalination permeates are slightly acidic, contain very low buffering capacity, and are very soft. As such, the water may be aggressive and corrosive to infrastructure, resulting in adverse health and economic effects. Consequently, a post-treatment step in which the chemical stability, buffering capacity and mineral content of the water is adjusted, is invariably practiced. This chapter reviews the knowledge accumulated in the last decades on desalination post-treatment processes. It covers fundamental chemistry aspects related to the aqueous, gaseous and solid phases relevant to post-treatment processes. The chapter also provides a thorough explanation on required water quality criteria; the advantages and disadvantages of currently applied post-treatment processes are detailed, engineering and cost considerations are discussed, state of the art post-treatment alternatives are covered, and contemporary research trends are listed.