Combining magnesium ammonium phosphate precipitation with membrane processes for ammonia removal from methanogenic leachates

Abstract

Chemical precipitation of ammonia as magnesium ammonium phosphate (MAP) from methanogenic leachates can be a competitive alternative to biological ammonia removal. Potential for trading of the precipitate as a fertiliser defines the economics of the process. The precipitate from a landfill leachate often containing organics and heavy metals as impurities with unknown risks limits its possibility for agricultural use. This study combines MAP precipitation with membrane processes and investigates the influence of wastewater matrix, solution pH and dosage ratio of chemicals (Mg2+ : PO43−) on the precipitate purity through lab scale semibatch experiments. Under similar experimental conditions (pH 8.5 and 1 : 1 Mg2+ : PO43− molar dosage), the precipitates from raw leachate and nanofiltration (NF) permeate showed MAP contents of 65 and 90%, respectively, correspondingly with about 8300 and 1600 mg TOC/kgprecipitate. For precipitation from NF permeate, precipitation at pH 8.0 with 1 : 1 dosage ratio and pH 8.5 with 1 : 0.9 dosage ratio gave precipitates each with about 97% purity.

Comparison of NF-RO and RO-NF for the Treatment of Mature Landfill Leachates: A Guide for Landfill Operators

“…Nanofiltration placed before reverse osmosis can provide greater flexibility for ammonia removal, since the organic compounds can be selectively separated. Ramaswami et al [ 35 ] reported the ability to recover ammonia from nanofiltration permeate of raw leachate as clean and useable struvite, which can be sold as a fertilizer. Since organics and hardness contents in the NF permeate are low, stripping of ammonia from RO retentate of NF permeate can be accomplished without significant foaming and scaling problems, which is often faced during ammonia stripping from leachates [ 58 , 59 , 60 ].…”

“…At the Ihlenberg landfill, the raw leachate (see composition in Table 2 ) gets about five times concentrated by the two-stage reverse osmosis (about 30, 15, 4, and 3 g/L Cl − , Na + , TOC and NH 4 + -N, respectively, in RO retentate). For this scenario for instance, biological treatment of RO retentate or its NF permeate would be challenging due to high salinity and the purity of struvite precipitated from the NF permeate of RO-NF would be lower [ 35 ].…”

“…However, no study could be identified, which investigated a combination of NF and RO (NF-RO) for treating landfill leachates. Integration of technologies has been emphasized for achieving efficient and economic treatment of landfill leachates [ 24 , 28 , 32 , 33 , 34 , 35 ], which could also offer more flexibility and advantages for the individual processes in the process chain [ 35 ].…”

Performance of integrated sequencing batch reactor (SBR) and reverse osmosis (RO) process for leachate treatment: effect of pH

“…One of the main environmental problems arising during solid waste landfilling is the generation of heavily polluted landfill leachates [3]. They are highly loaded wastewater containing a wide variety of pollutants, including organic compounds, heavy metals and inorganic salts [1,[3][4][5]. The concentration of most components in landfill leachate exceed the concentration of the same in the sewage sludge [2].…”

Editorial

“…), energy in the water sector (McNabola ) and engineered treatment systems (Patziger & Kiss ; Ramaswami et al . ). Our proposition is to refresh the ambition of the journal to re‐emphasise this unique contribution, whilst also launching several new publication initiatives in support of this vision.…”