Effluent dissolved organic nitrogen and dissolved phosphorus removal by enhanced coagulation and microfiltration

Area of Science:

• Environmental Engineering
• Water Treatment Technologies
• Nutrient Removal

Background:

• Achieving very low effluent nutrient levels (<3 mg N/L for N, <0.1 mg P/L for P) requires addressing previously unaccounted effluent fractions.
• Dissolved organic nitrogen (DON) and dissolved non-reactive phosphorus (DNRP) are significant fractions impacting overall nutrient removal.

Purpose of the Study:

• To investigate the simultaneous removal of effluent DON and dissolved phosphorus (DP) using enhanced coagulation with alum followed by microfiltration.
• To develop a simple and accurate measurement protocol for dissolved nitrogen (N) and phosphorus (P) species at very low concentrations.

Main Methods:

• Enhanced coagulation using alum at tertiary phosphorus removal doses.
• Microfiltration with 0.22 μm pore size filters.
• Development and validation of a simultaneous digestion protocol for DON and DNRP analysis.

Main Results:

• Maximum simultaneous removal of DON (69%) and DP (72%) was achieved at an alum dose of approximately 3.2 mg Al(III)/L.
• Residual DON and DP concentrations were reduced to 0.3 mg N/L and 0.25 mg P/L, respectively.
• DNRP removal followed similar trends to dissolved reactive phosphorus.

Conclusions:

• Enhanced coagulation and microfiltration are effective for removing DON and DP fractions to meet stringent nutrient discharge limits.
• The developed analytical protocol provides a reliable and accurate method for quantifying low-level dissolved N and P species in wastewater.
• This approach contributes to advanced wastewater treatment strategies for minimizing nutrient pollution.