Small Sewage Treatment Works Research Articles

Can an Integrated Constructed Wetland in Norfolk Reduce Nutrient Concentrations and Promote In Situ Bird Species Richness?

Integrated Constructed Wetlands (ICWs) are potentially effective tools in the effort to restore aquatic ecosystems, and also they incorporate multiple co-benefits. An ICW was constructed in Norfolk, UK, to address the degradation of a stream and lake receiving treated effluent from a small Sewage Treatment Works (STW). Results demonstrated that: (1) nutrient concentrations significantly reduced from the ICW influent to the effluent (percentage reductions: total phosphorus [TP]: 78%, orthophosphate: 80%, total oxidised nitrogen [TON]: 65%, nitrate: 65%, nitrite: 67%, ammoniacal nitrogen: 62%), and mean dissolved oxygen concentrations increased (influent mean: 6.4 ± 1.4 mg l−1 effluent mean: 17.8 ± 3.3 mg l−1), (2) there were non-significant reductions in nutrient concentrations in the receiving stream (percentage reductions: TP: 23%, orthophosphate: 23%, TON: 26%, nitrate: 26%), with the exception of ammoniacal nitrogen (127% increase) and nitrite (76%) after ICW commissioning, and (3) mean in situ avian species richness increased from 10 to 27 species. Thus, the ICW substantially reduced nutrient concentrations, and had in situ conservation benefits. It is recommended that appropriately designed ICWs should be implemented widely and statutory authorities should ensure: 1) best-practice maintenance and 2) final effluent monitoring at both the STW and at the ICW outflows.

Phosphorus and Emerging Micro-pollutants in Surface Waters: Challenges and Prospects for Water Quality Improvements

An oversupply of Phosphorus in water bodies accelerates growth of algae and higher forms of plant life to produce undesirable impacts on overall water quality. Phosphorus inputs to surface waters arise from a variety of point and nonpoint sources. However much of the P is contributed by agricultural runoff and outfall of treated (or untreated) wastewater in receiving water-bodies. Point sourced-P inputs to waters have considerably decreased in recent years, at least partly driven by regulatory requirements, e.g. the EU Water Framework Directive. This has largely been achieved by removing P from treated wastewaters at sewage treatment works (STWs). Studies have shown that introducing an additional treatment step (“P-stripping”) can significantly reduce P in STW outfalls. Given P deposits are depleting, there is much interest in phosphorus recovery from wastewaters. A few STWs have already started to recover P as struvite (NH4MgPO4.6H2O) mineral – a substitute for commercially produced P-fertilizers. This requires major investment and is not economically viable at small STWs. Nonetheless it is a major breakthrough in terms of P recovery and its use. Effluents from sewage treatment works (STW) can often contain a complex mixture of residual microcontaminants, not removed during wastewater treatment. Organic micro-pollutants have been found in rivers receiving STW effluents. Such residual contaminants have become the focus of an emerging field of water quality study and are collectively referred to as pharmaceuticals and other personal healthcare products, PPHCPs. Many of these chemicals have the ability to effect the hormonal signaling of organisms and are called endocrine disrupting compounds (EDC). Such chemicals have shown some of the most damaging biological effects in aquatic organisms. Biological effects in the aquatic environment are typically related to the development of intersex in fish. Recent research shows the use of STW practices such as upgrading from using a combined trickling filter contact process to activated sludge treatment, ozonation, membrane filtration and use of suspended biofilm reactors reduces the amount of EDCs in waste effluent. It is thus possible to remove contaminants from STW effluents, but it will not be possible without major infrastructure improvements. This paper presents the challenges and prospects of P and micro-organic pollutants in surface waters.

The effect of farming practices on phosphorus transfer to a headwater stream in England

Characterization of phosphorus (P) sources in catchments is critical to the restoration of stream integrity following eutrophication. To better understand the effects of farming practices on P transfer in a small rural mixed farming catchment (Rosemaund), spatial and temporal patterns in P delivered from a field-drain (Foxbridge, 6 ha), and to two downstream stations (Jubilee, 31 ha and Belmont, 150 ha) were investigated in relation to detailed records on cultivation practices and fertilizer/manure P inputs over a 3-year period (1997–2000) with above-average rainfall. The Belmont catchment also included a farmstead and a small sewage treatment works (STW). The main source of P in drainflow (December–April) was the soil with flow-weighted concentrations of particulate P (PP) up to 2 mg L −1 and concentrations of dissolved-reactive P (DRP) (0.1–0.4 mg DRP L −1) above current riverine targets to limit eutrophication. Agricultural operations carried out in autumn/early winter sporadically increased concentrations of DRP (fertilizer/manure applications) and PP (cultivations) in drain/stream discharge, but only during events that produced small amounts of stormflow. Occasionally large DRP and PP concentrations in drainflow were also recorded during the ecologically sensitive summer months, but this was unrelated to any farming practice. Stream P concentrations were further influenced by processes of baseflow dilution, in-stream retention/release and discharges from the STW and farmstead. The results highlight the disparity between the timing of farming operations at this site (autumn/early winter), the main period of land drainage (winter/spring) and the main period of biological activity (spring and summer). A greater understanding of the ecological significance of variably timed P inputs to headwater streams is needed to develop effective catchment management.

Spatial contributions of diffuse inputs and within-channel processes to the form of stream water phosphorus over storm events

Summary Concentrations of suspended particulate matter (SPM), NO 3 -N and P fractions: PO 4 -P, dissolved organic P (DOP), particulate P (PP) and bioavailable exchangeable P were examined over 5 storm events in two nested agricultural catchments in NE Scotland: a (51 km 2 ) catchment and its headwater (4 km 2 ). NO 3 -N showed anticlockwise hysteresis for all storms in both catchments. In contrast, the headwater showed strong clockwise hysteresis of SPM, dissolved and particulate P concentrations, but which weakened through summer to spring. Less pronounced hysteresis of P forms in the larger catchment was attributed to a combination of factors: a less energetic system, nutrient leaching from the floodplain, a point source of a small sewage treatment works and the occurrence of coarser soil and sediment parent materials with less P adsorption and transport capacity. The headwater exhibited a strong ‘first flush’ effect of sediment and dissolved P, particularly following dry conditions, received a significant transfer of readily-solubilized organic P from the surrounding soils in late summer and after manure applications in winter, and was the likely cause of large sediment associated P signals observed in the 51 km 2 catchment. Our results suggest that steeper gradient headwaters should be targeted for riparian improvements to mitigate soil erosion from headwater fields. The efficiency of riparian erosion controls is also dependant on the size of the store of fine sediment material within the stream channel and this may be large.

Small sewage treatment works using a fenton oxidation method

This paper describes an oxidation treatment of Domestic Wastewater (DW) using Fenton's reagent (H2O2/Fe2+). In this technique, DW was mixed with ferrous sulfate (523 mg 1‐1) and hydrogen peroxide (300, 600 and 900 mg l‐1 respectively). Due to the strong oxidizing potential of the hydroxyl radicals and other oxidants the organic pollutants and nutrients (organic nitrogen, phosphorous) were wet oxidized to carbon dioxide, and nitrogen oxides and phosphorous was precipitated as Fe3(PO4)2. Experiments were run in a batch, laboratory‐scale, pilot‐plant, at 30°C and the efficiency of oxidation was studied in relation to oxidation time. According to the experimental results a 82% COD reduction, a 80% BOD5 reduction, a 100% fats and oils reduction, a 95% Total Kjeldahl Nitrogen (TKN) reduction, a 96% Total Suspended Solids (TSS) reduction and a 93% total phosphorous reduction were achieved. It is concluded that the application of chemical oxidation of DW is more advantageous compared to conventional biological treatment especially for small works.

The advantages of a constructed reed bed based strategy for small sewage treatment works

The advantages of the use by a major UK water utility serving 8 million people in central England of constructed subsurface flow reed beds for secondary, tertiary and storm water treatment at small sewage treatment works is placed in context with improved permit compliance to more stringent standards and a continuing downward pressure on operating costs. Capital and energy costs are compared with the competing tertiary treatment process of recirculating sand filtration. Further economic advantage is gained by combining tertiary treatment and stormwater treatment. With over 160 sites in operation by mid 1997 the success of the strategy has given confidence to allow for the early or emergency installation of reed beds to improve or maintain effluent quality before replacement, or in one case the provision, of secondary treatment. Use of constructed reed beds is now being extended to larger facilities where only a proportion of the flow needs to be treated to achieve standards. For tertiary treatment reed beds there is an additional environmental benefit with the typical removal of 10.7 mg/l of total nitrogen.

The advantages of a constructed reed bed based strategy for small sewage treatment works

The advantages of the use by a major UK water utility serving 8 million people in central England of constructed subsurface flow reed beds for secondary, tertiary and storm water treatment at small sewage treatment works is placed in context with improved permit compliance to more stringent standards and a continuing downward pressure on operating costs. Capital and energy costs are compared with the competing tertiary treatment process of recirculating sand filtration. Further economic advantage is gained by combining tertiary treatment and stormwater treatment.With over 160 sites in operation by mid 1997 the success of the strategy has given confidence to allow for the early or emergency installation of reed beds to improve or maintain effluent quality before replacement, or in one case the provision, of secondary treatment. Use of constructed reed beds is now being extended to larger facilities where only a proportion of the flow needs to be treated to achieve standards. For tertiary treatment reed beds there is an additional environmental benefit with the typical removal of 10.7 mg/l of total nitrogen.

Estrogenic activity in five United Kingdom rivers detected by measurement of vitellogenesis in caged male trout

AbstractIt was recently demonstrated that most, if not all, effluents of sewage‐treatment works (STWs) in the United Kingdom are estrogenic to fish. As many STWs discharge into rivers, it is possible that some stretches of rivers downstream of where the effluent enters might also be estrogenic. To assess this possibility, the induction of vitellogenin synthesis in caged male trout placed at various distances downstream of the effluent entry point was used as a biomarker of estrogen exposure. Individual discharges into five rivers in England were studied. In four cases, fish placed in the neat effluent, or close to where it entered a river, showed very marked and rapid increases in their plasma vitellogenin concentrations, demonstrating that the effluent was estrogenic. In two of these four cases, none of the downstream sites were estrogenic, whereas in one of the four, fish placed at a site 1.5 km downstream did respond by synthesizing appreciable amounts of vitellogenin, although sites further downstream were not estrogenic. The situation in the fourth river was quite different; not only was the effluent extremely estrogenic (a maximum vitellogenin response in the mg/ml range was attained), but so were all the other study sites on the river, the last of which was 5 km downstream of where the effluent entered. This particular river receives trade effluent from wool‐scouring mills, which contains much higher concentrations of alkylphenolic chemicals than any of the other discharges studied. It is suggested that these chemicals probably account for the estrogenic activity of this river. The final (fifth) river showed no estrogenic activity, not even in the neat effluent. This discharge comes from a very small STW, which receives no trade waste, and one or both of these factors may account for why the effluent (and hence the river) was not estrogenic.

Standardisation of Small Wastewater Treatment Plants for Rapid Design and Implementation

Severn Trent Water was faced with the problem of rapidly implementing a massive capital investment programme to replace a large number of its small sewage treatment works. To meet the investment targets it was necessary to streamline the process of planning, design, construction and overall procurement of plant and equipment. Key elements in achieving these targets were seen as:Standardisation of treatment processes and plant to reduce design times and construction periods and to guarantee performance.Use of standard specifications and procurement practice to ensure rapid acquisition of plant to the required design standards. The Company's experience of operating a large number of different types of sewage treatment plant was used to standardise treatment processes for small works on the rotating biological contactor (RBC) and the reed bed.

The phytoplankton of an enriched, soft‐water lake subject to intermittent hydraulic flushing (Grasmere, English Lake District)

SUMMARY. 1. The abundance and species composition of the phytoplankton of Grasmere were monitored over a 12‐year period following the commissioning of a small sewage treatment works, upstream of the lake.2. Although Grasmere has been subject to increased phosphorus‐loading and has quickly developed many features associated with eutrophication, the composition of its plankton has retained the characteristics of a mesotrophic, soft‐water lake: a vernal diatom maximum, generally dominated by Asterionella, is followed by summer growths of nanoplanktonic species, of various colonial Chlorophyceae, before a substantial return to Asterionella‐dominance in the autumn. In cooler summers there have been episodes of renewed diatom growth. followed by truncated recapitulations of the essential summer sequence. Anabaena solitaria was relatively common in drier summers when dissolved inorganic nitrogen fell to low concentrations, although many of the ‘larger’ algal species associated with stratified eutrophic lakes (Aphanizomenon, Microcystis, Ceratium spp.) have failed to become abundant in Grasmere.3. Mean biomass levels (as indicated by chlorophyll concentration) have increased in response to the enrichment, though they do not conform well with most chlorophyll/phosphorus regression‐models.4. The key factor resisting a more complete transition to a typical eutrophic plankton appears to be the efficiency of episodic flushing of the lake during periods of high fluvial discharge sustained by heavy rainfall over the extensive, mountainous catchment. The probabilities that these limnological conditions might fail to deter the development of ‘nuisance’ blooms are briefly assessed.