Presentation on theme: "This work was funded by CHERUB Environmental and Educational Projects Ltd. S c i e n c e f o r A g r i c u l t u r e a n d t h e E n v i r o n m e n t."— Presentation transcript:
This work was funded by CHERUB Environmental and Educational Projects Ltd. S c i e n c e f o r A g r i c u l t u r e a n d t h e E n v i r o n m e n t A Novel Biological Phosphate Pump Julian Greaves, Phil Haygarth & Phil Hobbs Institute of Grassland and Environmental Research,North Wyke Research Station, Okehampton, Devon, EX20 2SB, UK. Abstract Introduction Apparatus Methods Process description:- Following the introduction of a dilute influent, an anaerobic period promotes the production of short chain fatty acids (SCFAs) such as acetate. Uptake of SCFAs by the phosphorus accumulating microflora (PAM) promotes the release of P into the liquid phase and enables excess uptake of P in the subsequent aerobic phase (fig.1). Effluent discharge takes place following a period of settlement, while P remains trapped in the sludge solids. Subsequent influent introduction provides the PAM with a carbon source to promote the release of stored P. Released P accumulates in the aqueous phase together with the fresh influent P. Subsequent cycles enable the stepwise accumulation of P in the reactor until the PAM’s capacity for P storage is taken up. At this point the addition of a carbon source such as acetate followed by an extended anaerobic period promotes the release of all stored P into a carbon depleted, denitrified effluent. Samples were taken at the end of each aerobic and anaerobic period for P, NO 3 and NH 4 analysis. Fig. 1 Experimental parameters Influent P concentration - 11.7 mg l -1 Influent quantity - 7.5 l P addition per cycle - 87.7 mg P increase per cycle - 2.9 mg l -1 Results Fig.2 Phosphorus behaviour over five cycles. Fig.3 Phosphorus release after eleven cycles Conclusions This work demonstrates the potential for EBPR to be used as a biological pump to increase the concentration of P, from a dilute influent into a clean effluent, from which recovery of a high quality P rich product would be possible. Currently ca. 120,000 t p.a. of P is collected as manure in housed animal and dairy production units in the UK. Of this ca. 26,000 t of P is collected as slurry. Following a period of storage, over 60% of this can be extracted by dilution with water and is thereby potentially available for recovery. This represents approximately 70% of the UK non-agricultural P requirement. Treatment of animal manures to reduce their environmental impact is becoming widespread and increasingly required under EU legislation. The treatment system presented here addresses the requirements of discharge consents while simultaneously producing a clean source of recoverable P. Such a system has the potential to supply the P industry with a substantial proportion of its overall needs. This system has been developed as part of a research project investigating P recovery from animal wastes. However, the process uses a manipulation of standard wastewater treatment procedures and is therefore likely to be effective for a wide range of influent sources including municipal sewage. An innovative manipulation of the standard Enhanced Biological Phosphorus Removal (EBPR) process configuration was used to increase the concentration of (P) by three times. Four replicate Sequencing Batch Reactors (SBRs) with a working volume of 30 l, were used to treat an influent stream of dilute pig slurry. We expect that this system could be used to generate P concentrations exceeding 100 mg l-1. Phosphorus was accumulated in the reactors from 11.7 mg l -1 in the influent to 29.6 mg l -1 in the final effluent over eleven cycles.