Abstract
The novel automatic flow system, direct-injection detector (DID) integrated with multi-pumping flow system (MPFS), dedicated for the photometric determination of orthophosphates in wastewater and freshwater samples is for the first time described. All reagents and the sample were injected simultaneously, in counter-current into the reaction-detection chamber by the system of specially selected for this purpose solenoid micro-pumps. The micro-pumps provided good precision and accuracy of the injected volumes. For the determination of orthophosphates, the molybdenum blue method was employed. The developed method can be used to detect orthophosphate in the range 0.1–12 mg L−1, with the repeatability (RSD) about 2.2% at 4 mg L−1 and a very high injection throughput of 120 injections h−1. It was possible to achieve a very small consumption of reagents (10 μL of ammonium molybdate and 10 μL of ascorbic acid) and sample (20 μL). The volume of generated waste was only 440 μL per analysis. The method has been successfully applied, giving a good accuracy, to determination of orthophosphates in complex matrix samples: treated wastewater, lake water and reference sample of groundwater. The developed system is compact, small in both size and weight, requires 12 V in supply voltage, which are desirable for truly portable equipment used in routine analysis. The simplicity of the system should result in its greater long-time reliability comparing to other flow methods previously described.
Highlights
Phosphorus is an essential nutrient for plants, animals and humans
Phosphorus removal is essential in wastewater treatment and should be monitored
In our previous publications and patent, we described a novel type of photometric detector—direct-injection detector (DID) integrated with an multi-pumping flow system (MPFS) system (Kalinowski and Koronkiewicz 2016; Koronkiewicz and Kalinowski 2011; Koronkiewicz and Kalinowski 2012) which can considerably simplify an analytical flow procedure and allow for reduction in the sample and reagent consumption
Summary
Phosphorus is an essential nutrient for plants, animals and humans. It is beneficial to many biological processes in the environment. Too much phosphate in water can contribute to eutrophication. Phosphorus removal is essential in wastewater treatment and should be monitored. Knowledge of the concentration of phosphorus, along with related physico-chemical data, can assist in controlling the wastewater treatment plant (WWTP) so that efficient removal is achieved. One of the potential applications of online analyses is controlled dosing of coagulants (e.g. iron and aluminium salts) in chemical sewage treatment plants (Benson et al 1996). An online phosphorus analyser would contribute to the most costefficient work of a treatment plant and reduce the phosphorus content to an acceptable level in terms of both the quality of receiving water and legal requirements
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