Combined seawater toilet flushing and urine separation for economic phosphorus recovery and nitrogen removal: a laboratory-scale trial

Freshwater toilet flushing consumes 20-35% of typical household water demand. Seawater toilet flushing, as practised by Hong Kong since 1958, provides an alternative water source. To maximise the benefits of this unique dual water supply, urine separation could be combined to allow low-cost struvite...

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Bibliographic Details
Published in:Water science and technology 2014-01, Vol.70 (6), p.1065-1073
Main Authors: MACKEY, H. R, ZHENG, Y.-S, TANG, W.-T, DAI, J, CHEN, G.-H
Format: Article
Language:English
Subjects:
Ammonia
Applied sciences
Batch reactors
Chemical analysis
Denitrification
Economic conditions
Exact sciences and technology
Flushing
Flushing (water)
Fresh Water
Freshwater
Hong Kong
Hydraulic retention time
Inland water environment
Laboratories
Magnesium Compounds
Marine
Natural water pollution
Nitrification
Nitrogen - chemistry
Nitrogen removal
Phosphates
Phosphorus
Phosphorus - chemistry
Phosphorus removal
Pollution
Reactors
Recovery
Removal
Retention time
Sanitary Engineering - methods
Seawater
Seawaters, estuaries
Separation
Struvite
Urine
Urine - chemistry
Water analysis
Water demand
Water Pollutants, Chemical
Water supply
Water treatment and pollution
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Summary:Freshwater toilet flushing consumes 20-35% of typical household water demand. Seawater toilet flushing, as practised by Hong Kong since 1958, provides an alternative water source. To maximise the benefits of this unique dual water supply, urine separation could be combined to allow low-cost struvite production and subsequent urine nitrification - in-sewer denitrification. This paper reports on a laboratory-scale study of seawater urine phosphate recovery (SUPR) and seawater-urine nitrification. A laboratory-scale SUPR reactor was run under three phases with hydraulic retention time between 1.5 and 6 h, achieving 91-96% phosphorus recovery. A urine nitrification sequencing batch reactor (UNSBR) was also run for a period of over 650 days, averaging 90% ammonia removal and loading of up to 750 mg-N/L.d. Careful control of the SUPR phosphate removal was found necessary for operation of the downstream UNSBR, and system integration considerations are discussed.
ISSN:0273-1223
1996-9732
DOI:10.2166/wst.2014.335