SUMMARY FINDINGS

NUI Galway was contracted by Clean Water Technology Ltd. (CWT) to carry out a 5-day detailed study on the performance of a phosphorus (P) removal technology using a new adsorption filter media, CWTMedia, at an existing municipal wastewater treatment plant for about 250 persons. The study findings were as follows:

1.      Effluent from the CWTMedia technology remained below 0.03 mg PO₄-P/l until the average P loading exceeded 1.8 g PO₄-P/kg _media

2.     The adsorption capacity of the CWTMedia at 1.8 g PO₄-P/kg _media, compares most favourably with the capacities of commonly available P adsorption materials

3.      At a P supply rate of 1.2 g P/person.day, 179 kg of the CWTMedia practically adsorbs all the P produced by 268 persons in one day

4.   The CWTMedia can be readily and cost effectively regenerated and

5.   Since the phosphorus is precipitated seperately from the wastewater treatment biosolids, and at high pH values, the phosphorus precipitate could be used locally as a fertiliser.

Overall, the CWTMedia technology for removing phosphorus performed excellently and operated without problems for the 5-day monitoring period. The CWTMedia technology has great potential for eliminating the P enrichment of receiving waters.

BACKGROUND

An NUI Galway (Civil Engineering) research team was requested by Clean Water Technology (CWT) Ltd to carry out an investigation/validation study on a novel P removal technology using CWTMedia (CWTMedia technology). The technology was monitored over a 5-day period in November 2009 at a Wexford County Council wastewater treatment plant – Our Lady’s Island, Co. Wexford, Ireland – where the CWTMedia technology had been installed and operated by CWT Ltd since 2007.

PHOSPHORUS REMOVAL PERFORMANCE

An initial regeneration was carried out to ensure that the 179 kg of media in the CWTMedia technology was practically free of P. Effluent from the wastewater treatment plant was then pumped through the CWTMedia technology at an average initial concentration of 1.84 mg orthophosphate-phosphorus (PO₄-P)/l and was later increased to an average concentration of 6.9 mg PO₄-P/l, using sodium phosphate solution as a supplement, in order to more closely represent typical P concentrations in municipal wastewater. Multiple samples were taken over the 5-day testing period at a number of locations in the system and analysed for P. After 53 hours of operation, an ultimate breakthrough exceeding 0.03 mg PO₄-P/l occurred when over 72 m³ of water had passed through the CWTMedia technology. This breakthrough corresponds to an estimated adsorption capacity of 1.8 g PO₄-P/kg_media (typical published values for other materials are shown in the table below) or the daily production of 268 persons at 1.2 g P/person.day.

Adsorptive capacities of common phosphorus adsorption materials and CWTMedia

                                                                                Gravel                                                                           0.03-0.05

                                                                            Bottom ash                                                                           0.06

                                                                             Steel slag                                                                             0.38

                                                                       Blast furnace ash                                                                 0.40-0.45

                                                                                Fly ash                                                                                0.62

                                                                                 Shale                                                                                 0.75

                                                                                Laterite                                                                                0.75

                                                                                 Zeolite                                                                                1.00

                       Notes:1.Heal,K.V.,Smith,K.A.,Younger,P.L.,McHaffie,H.andBatty.L.C.(2004).PhosphorusinEnvironmental                                                                                                              Technologies: Principles & Applications. IWA  Publishing, UK. ISBN 1 84339 001 9                                                     

                                   2.Adsorbed P loading that had breakthrough concentrations less than 0.03 mg PO4-P/l

COST ESTIMATIONS

To achieve an effluent P concentration of 0.5 mg PO₄-P/l in a wastewater treatment plant, the CWTMedia technology is competitive in comparison with alternative P removal systems that include metal ion dosing, sand filtration, coated media and membrane technology. Based on a detailed study of a plant size of about 250 persons, it is estimated that for the CWTMedia technology, installed capital costs are competitive with costs for alternative P removal systems. It is further reckoned that CWTMedia technology costs should be competitive for larger populations. In the P removal performance study at the 250-person plant, the CWTMedia technology has been shown to readily achieve a consistent final effluent P concentration of less than or equal to 0.03 mg PO₄-P/l in a single-pass at practically the same cost as achieving 0.5 mg PO₄-P/l. Since the P is precipitated separately from the treatment plant biosolids with the CWTMedia technology, and at high ph values, the P precipitate could be used locally as a fertiliser.

Why not contact us for a quotation based on your specific needs.