Biology of polyphosphate-accumulating bacteria involved in enhanced biological phosphorus removal

Abstract

Recent research on the process of biological phosphorus removal in lab-scale treatment systems has indicated that: (i) the development of an actively polyP-accumulating bacterial community after the introduction of an anaerobic period may take at least 4 months; (ii) up to 80% of all aerobic bacteria isolated from these communities are able to accumulate polyP; (iii) polyP synthesized by the bacterial communities of lab-scale treatment systems is probably mainly low polymeric, not exceeding 20 P-residues, and this polyP is rapidly degraded during the anaerobic period; (iv) the enzymatic hydrolysis of polyP under anaerobic conditions is accompanied by PHB formation from exogenous acetate, reducing equivalents are provided by the degradation of carbohydrates; and (v) nitric oxide inhibits the release of phosphate under anaerobic conditions in Renpho and F&D sludges. Bacteria belonging to the genus Acinetobacter occur in a wide variety of activated sludges in which enhanced biological phosphate removal is observed. A. johnsonii 210A was studied in detail with respect to the elemental composition of polyP granules, the enzymatic synthesis and degradation of polyP, the regulation of polyP metabolism, and the transport of phosphate. A. johnsonii 210A reflects activated sludge in a number of ways as far as polyP metabolism is concerned but its polyP is highly polymeric and the phosphate efflux rate under anaerobic conditions is relatively low and not increased by exogenous acetate. In addition to Acinetobacter, other polyP-accumulating microorganisms may be involved in biological phosphorus removal. The isolation of polyP-accumulating denitrifying bacteria may well have interesting implications for a new process design in wastewater treatment systems. Further studies on the enzymes involved in polyP biosynthesis and on the uptake and efflux systems of phosphate, potassium, magnesium and lower fatty acids in pure cultures will enlarge our insight in the energetics of the metabolism of polyP. In addition, the regulation of the metabolism of polyP-accumulating organisms needs to be studied in more detail.

The Impact of Microbial Ecology and Chemical Profile on the Enhanced Biological Phosphorus Removal (EBPR) Process: A Case Study of Northern Wastewater Treatment Works, Johannesburg

“…Eutrophication, known as excessive microbial growth, results in reduced transparency, reduced photosynthetic activity, depletion of oxygen, production of toxic compounds and loss of plant and animal species [6]. Korstee and co-authors [7] reported that no eutrophication occurs when the phosphorus concentration is reduced to between 8 µg/L and 10 µg/L, even at nitrogen concentrations of as high as 4 mg/L to 5 mg/L. Generally, municipal wastewater systems are the major sources of phosphorus when compared to other sources of water pollution [8].…”

The microbiology of biological phosphorus removal in activated sludge systems

“…Eutrophication is a global problem, in which blooms of cyanobacteria and eukaryotic algae occur as a consequence of the breakdown of community homeostasis from continued pollution of oligotrophic aquatic bodies with nutrients like nitrogen (N) and phosphorus (P) at levels which exceed growth-limiting concentrations for these photosynthetic organisms [1,2]. Of these nutrients, P input is considered more critical [3,4] since many of the cyanobacteria are diazotrophic, capable of satisfying their N requirements from ¢xation of atmospheric N 2 . The problems caused by eutrophication have been discussed frequently in the literature, e.g.…”

“…Increasing evidence points to wastewater treatment plants as major point sources for both N and P, which in the latter case originates from fecal material, industrial and commercial sources and synthetic detergents and other cleaning products [5]. Conventional activated sludge plants designed principally to remove organic carbona-ceous material produce treated e¥uents with high residual P levels, although some N removal does occur in these systems [3,6,11]. In the past 30 years many plants have been designed and built around the world to deliberately reduce not just organic carbon and N levels but also P, using microbially based methods [11^14].…”

Sediment phosphorus speciation and mobility under dynamic redox conditions

“…The P requirements by the microbial community are also likely to be high during the transition to aerobic conditions due to the availability of O 2 as an energetically efficient electron acceptor and fermentation products (SCFA), further decreasing the probability of polyphosphate accumulation. Additionally, polyphosphate accumulation and release has shown to be inhibited by denitrification and sulfate reduction due to competition for SCFA (Kortstee et al, 1994;Yamamoto-Ikemoto et al, 1994).…”