Sewage Streams Research Articles

Event-driven model predictive control of sewage pumping stations for sulfide mitigation in sewer networks

Chemicals such as Mg(OH)2 and iron salts are widely dosed to sewage for mitigating sulfide-induced corrosion and odour problems in sewer networks. The chemical dosing rate is usually not automatically controlled but profiled based on experience of operators, often resulting in over- or under-dosing. Even though on-line control algorithms for chemical dosing in single pipes have been developed recently, network-wide control algorithms are currently not available. The key challenge is that a sewer network is typically wide-spread comprising many interconnected sewer pipes and pumping stations, making network-wide sulfide mitigation with a relatively limited number of dosing points challenging. In this paper, we propose and demonstrate an Event-driven Model Predictive Control (EMPC) methodology, which controls the flows of sewage streams containing the dosed chemical to ensure desirable distribution of the dosed chemical throughout the pipe sections of interests. First of all, a network-state model is proposed to predict the chemical concentration in a network. An EMPC algorithm is then designed to coordinate sewage pumping station operations to ensure desirable chemical distribution in the network. The performance of the proposed control methodology is demonstrated by applying the designed algorithm to a real sewer network simulated with the well-established SeweX model using real sewage flow and characteristics data. The EMPC strategy significantly improved the sulfide mitigation performance with the same chemical consumption, compared to the current practice.

SEWERAGE CATCHMENT STUDY FOR CLAN JETTIES, PENANG

The Water Pollution Study concluded that the most contaminated zone is the stretch where the fundamental channels meet the Clan Jetties shores. These are the channels along Lebuh Chulia, Gat Lebuh Armenian and Gat Lebuh Melayu. The organic loads, measured as far as BOD, COD, Oil & Grease, Suspended Solids are most noteworthy along this strip took after by the shoreline strip. The high E Coli concentrations along these 2 strips affirmed that there is fecal contamination most likely from the partially treated sewage being released from the unsewered premises nearby the Clan Jetties shore. This contamination is exacerbated by the direct sewage transfer into the ocean by the Clan jetties community because of the non-presence of any sewerage system at all. The usage of sewerage system must be provided as soon as possible and may be implemented in stages based on the budget and by doing in stages, the workability of the new system can be enhanced and redesigned in the subsequent stages. Since the houses are based on the ocean floor, the most suitable system to tap the sewage stream from the houses is the Vacuum Sewer System.

Integrating food webs with metabolic networks: modeling contaminant degradation in marine ecosystems.

Integrating food webs with metabolic networks: modeling contaminant degradation in marine ecosystems.

A New Approach for Mitigating Biofouling by Promoting Online Cleaning Using a Sacrificial Paraffin Coating

The presence of biofouling layers on heat transfer surfaces can reduce heat transfer efficiency markedly. A new method for inhibiting biofouling growth and promoting rapid online cleaning for heat exchangers recovering thermal energy from treated sewage streams based on a temporary coating is reported. A paraffin wax coating is cast in place without needing to disassemble the device, while the low roughness and the hydrophobicity of the coating inhibit bacterial growth. The coating and any attached biofouling can be removed by raising the surface temperature above the wax melting point. The effectiveness of this online cleaning and inhibition strategy was investigated using a simple laboratory test channel, representing a plate heat exchanger, and a process stream simulating treated sewage. The thermal resistance was monitored and showed that the reduction in biofouling thermal resistance eventually outweighed the additional thermal resistance resulting from the coating. A techno-economic analysis is presented to quantify the advantages of the paraffin coating method in terms of energy saving and cost reduction.

Different susceptibilities of bacterial community to silver nanoparticles in wastewater treatment systems

The release of silver (Ag) nanoparticles (NPs) into sewage streams has heightened concerns about potential adverse impacts on wastewater treatment processes. Here, we show that the rate constants of both biological nitrification and organic oxidation decreased exponentially with an increase in the Ag NP concentration, but nitrification was more severely inhibited than the organic oxidation even at low Ag NP concentrations (<1 mg Ag L−1) in batch experiments. The long-term exposure effects of Ag NPs on activated sludge bacteria were evaluated in sequencing batch reactors (SBRs) fed with two different substrates favoring heterotrophic and autotrophic bacteria. From a continuous operation for 50 days, it was found that heterotrophic bacteria in the organic removal process have higher tolerance to Ag NPs than do nitrifying bacteria. The effects of Ag NPs on the microbial community in both SBRs were analyzed using 16S ribosomal ribonucleic acid (rRNA) gene sequences obtained from pyrosequencing. The results showed that the level of microbial susceptibility is different for each type of microorganism and that the microbial diversity decreased dramatically after continuous exposure to Ag NPs for 50 days, resulting in a decrease of wastewater treatment efficiency.

Experimental investigation of interactions between the temperature field and biofouling in a synthetic treated sewage stream

Biofouling causes significant losses in efficiency in heat exchangers recovering waste heat from treated sewage. The influence of the temperature field on biofouling was investigated using a flat plate heat exchanger which simulated the channels in a plate and frame unit. The test surface was a 316 stainless steel plate, and a solution of Bacillus sp. and Aeromonas sp. was used as a model process liquid. The test cell was operated under co-current, counter-current, and constant wall temperature configurations, which gave different temperature distributions. Biofouling was monitored via changes in heat transfer and biofilm thickness. The effect of uniform temperature on biofouling formation was similar to the effect of uniform temperature on planktonic growth of the organisms. Further results showed that the temperature field, and particularly the wall temperature, influenced the rate of biofouling strongly. The importance of wall temperature suggests that fouling could be mitigated by using different configurations in summer and winter.

Stream Division by a Channel Bottom Orifice

Abstract A particularly important application of devices dividing a stream of liquid is in storm water drainage systems. Dividers of rainwater sewage streams have in recent years aroused considerable interest among producers of separators. It is therefore important to develop mathematically simple and, if possible, physically precise methods of sizing such structures. It is all the more important given that there are few such methods in the literature on hydraulics. This work is meant to partially remedy this deficiency by elaborating on the calculation methodology and by verifying it empirically. A circular orifice at the bottom of the supplying channel is technically the simplest type of stream divider (which makes it higly practical and particularly appealing to producers). A procedure for dimensioning the structure under consideration is proposed here. It is formally simple, being meant as a practical designing tool. This proposal has been verified experimentally. The degree of the division of the stream was measured in a laboratory model. The main issues were the stability of the characteristics of the lateral outflow and the possibility of applying the classical equations of hydraulics to size the type of divider considered here. In both cases the results obtained may be regarded as positive. Admittedly, the output of the lateral outflow exceeds the nominal value for greater inflows Qp, but it is at most double the nominal value. From a technical point of view, this may be regarded as a good result, considering the simplicity of the system. The answer to the second issue proved even more satisfactory. It turns out that the formally simple hydraulics relationships provide a technically consistency of theory with measurement results. Thus the designing of objective devices does not require the application of difficult, time-consuming and costly methodology.

STUDIES ON THE BIOLOGICAL TREATMENT OF INDUSTRIAL WASTEWATER STREAMS

Two experimental periods have been undertaken to investigate the biodegradability of sewage streams (mainly regarding the organic substances) produced by a gas cartridge production, filling and distribution company. A sequencing batch reactor (SBR) was used for the laboratory examinations launched with municipal sewage sludge with a concentration of approx. 3 g MLSS/L. The various conditions in the reactors followed each other cyclically (fill, anoxic, aerobic, settle, draw) three times a day. The anoxic to aerobic time ratio was ~1:3. First, an emulsion sewage stream was studied (cartridge production). The adaptation of microorganisms resulted in the increase of the organic compound removal from 0.07 gCOD/(gMLVSS*d) to 0.2 gCOD/(gMLVSS*d) parallel to increasing the hydraulic load. The other examined sewage stream was a 500 ppm activated MDEA (aMDEA – N-methyl-diethanolamine, used in gas sweetening processes). The SBR reactor was continuously loaded with sewage streams generated at the company, leaving enough time for the adaptation of microorganisms to the contaminants. In the last period, MDEA stream was also added, and then the previous sewage streams were taken away. In the last two weeks the influent was solely 500 ppm aMDEA. The removal efficiency of organic substances still remained over 95% with an effluent CODtot concentration below 50 mg/L. Oxygen uptake rate measurements were carried out with both sewage streams at the beginning of the experimental period and at the end of it (with the adapted sludge). The results obviously show the necessity of microbial adaptation in the biological treatment of special industrial sewage streams.

Will improving wastewater treatment impact shorebirds? Effects of sewage discharges on estuarine invertebrates and birds

AbstractHuman communities often discharge wastewaters into estuaries, influencing their organic and pollutant loading, benthic community and trophic structure. The implementation of the Water Framework Directive has encouraged the treatment of wastewater discharges across European estuaries, but the implications for invertebrate and waterbird communities are poorly understood. We explore the effects of untreated sewage discharges on the distribution and abundance of foraging black‐tailed godwits Limosa limosa and their main benthic prey (bivalves and polychaetes) on the Tejo estuary in Portugal, a major European Special Protection Area with ongoing wastewater improvements. Patches of mudflat in close proximity to sewage streams (&lt;30 m) can support polychaete densities and biomass that are an order of magnitude higher than more distant sites (&gt;70 m), and godwits foraging in these areas can attain the highest intake rates recorded for the estuary. However, high intake rates can also be attained on bivalve prey, and bivalve biomass and density increase slightly with distance from sewage streams. As the organic input from sewage outfalls influences invertebrate abundance and godwit foraging rates over relatively small areas, the ongoing implementation of a sewage treatment network on the Tejo estuary seems likely to have only a limited impact on the wintering godwit population. The localized effect of untreated sewage discharges on benthic communities suggests that the implications for predatory birds are relatively minor where alternative prey are available, but may be more severe in locations with more depauperate, polychaete‐dominated invertebrate communities.

Quantitative assessment of time dependent drug-use trends by the analysis of drugs and related metabolites in raw sewage

Background: Accurate and timely information on the scale and dynamics of drug consumption is important for assessing the needs of law enforcement and public health services in a community. Aims: This paper presents a detailed examination of a comprehensive sewage-sampling campaign for the purposes of increasing an understanding of the dynamics of drug-flows in sewage streams, and developing new methodology by which this technique can support traditional drug-use surveys. Methods: A total of 104 sewage samples were collected from a treatment plant servicing approximately 500 000 people and analysed for levels of methamphetamine, cocaine and cocaine metabolites. Careful examination of the kinetics of drug-flow profiles was then performed in order to identify trends or patterns of use within the community. Results: Results were validated against identical measurements of pharmaceutical reference compounds. Consumption profiles for cocaine and methamphetamine were found to differ in terms of frequency and timing of use. The majority of cocaine consumption occurs during the evening hours and 45% of consumption of this drug occurs in weekend periods. The flow of methamphetamine in the sewage system appears more evenly spread throughout the week. Conclusions: This result is consistent with both an extended excretion half-life and a pattern of use that is more evenly balanced across all days of the week. Comprehensive investigation in to the scale and kinetics of drug flow in a sewage stream can therefore provide valuable information, not only in terms of the volume of drug consumed, but also in terms of identifying differing usage-patterns over daily and weekly time-scales.

Analysis and Interpretation of Specific Ethanol Metabolites, Ethyl Sulfate, and Ethyl Glucuronide in Sewage Effluent for the Quantitative Measurement of Regional Alcohol Consumption

The quantitative measurement of urinary metabolites in sewage streams and the subsequent estimation of consumption rates of the parent compounds have previously been demonstrated for pharmaceuticals and narcotics. Ethyl sulfate and ethyl glucuronide are excreted in urine following the ingestion of alcohol, and are useful biomarkers for the identification of acute alcohol consumption. This study reports a novel ion-exchange-mediated chromatographic method for the quantitative measurement of ethyl sulfate and ethyl glucuronide in sewage effluent, and presents a novel calculation method for the purposes of relating the resulting sewage concentrations with rates of alcohol consumption in the region. A total of 100 sewage samples covering a 25-day period were collected from a treatment plant servicing approximately 500,000 people, and analyzed for levels of ethyl sulfate and ethyl glucuronide. The resulting data were then used to estimate combined alcohol consumption rates for the region, and the results were compared with alcohol related sales statistics for the same region. Ethyl glucuronide was found to be unstable in sewage effluent. Ethyl sulfate was stable and measurable in all samples at concentrations ranging from 16 to 246 nM. The highest concentrations of the alcohol biomarker were observed during weekend periods. Sixty one percent of the total mass of ethyl sulfate in sewage effluent corresponds to alcohol consumption on Friday and Saturday. Sales statistics for alcohol show that consumption in the region is approximately 6,750 kg/d. The quantity of ethyl sulfate passing through the sewage system is consistent with consumption of 4,900 to 7,800 kg/d. Sewage epidemiology assessments of ethyl sulfate can provide accurate estimates of community alcohol consumption, and detailed examination of the kinetics of this biomarker in sewage streams can also identify time-dependent trends in alcohol consumption patterns.

Occurrence and removal of pharmaceuticals in a municipal sewage treatment system in the south of Sweden

The occurrence and removal rate of seven pharmaceuticals (ibuprofen, naproxen, diclofenac, fluoxetine, ofloxacin, norfloxacin, ciprofloxacin), two metabolites (norfluoxetine, clofibric acid), one degradation product (4-isobutylacetophenone) and 3 estrogens (17α-ethinylestradiol, 17β-estradiol, estrone) were studied in the inlet and outlet of a tertiary sewage treatment plant (STP) in Sweden as well as between different treatment steps in the STP which includes a conventional activated sludge step. Pharmaceuticals in raw household and raw hospital sewage streams leading to the STP were as well investigated. Hydraulic retention times (HRT) of each treatment step was considered for sampling and for the calculation of the removal rates. These rates were above 90%, except for diclofenac, clofibric acid, estrone and ofloxacin. However, only diclofenac and naproxen showed significant effluent loads (> 145 mg/d/1000 inh). Diclofenac was not eliminated during the treatment and in fact even higher concentrations were found at the effluent than in the inlet of the STP. 17α-Ethinylestradiol was not detected in any of the samples. Results indicate that a STP such as the one in Kristianstad, Sweden, with a tertiary treatment is sufficient to remove significantly most of the investigated pharmaceuticals. The chemical treatment improved the removal of several pharmaceuticals especially the antibiotics, which showed step removal rates between 55 and 70%. The expected concentration levels of the pharmaceuticals in the surface water (dilution 1 to 10) close to the outlet of the STP are below the no-observed effect-concentration (NOEC). However, despite that this would imply no important effects in the aquatic environment one cannot rule out negative consequences nearby the STP because most of the NOEC values are derived from acute toxicity data. This may underestimate the real impact of pharmaceuticals in the aquatic ecosystem.

Hollow‐fibre supported liquid membrane extraction for determination of fluoxetine and norfluoxetine concentration at ultra trace level in sewage samples

In this study, a method was developed for determining the concentration of the pharmaceutical fluoxetine and its metabolite, norfluoxetine, in sewage water samples. Sample preparation was performed by hollow-fibre supported liquid membrane (HF-SLM) extraction with final analysis using liquid chromatography with UV detection. Several parameters were studied including type of organic solvent, sample and acceptor pH, and salt and humic acid content. The optimised method allowed determination of the analyte at the ng/L level in sewage water. A linear plot gave a correlation coefficient better than 0.991 for both analytes and resulted in limits of detection in sewage water of 11 and 12 ng/L, for fluoxetine and norfluoxetine, respectively. The enrichment factor was over 1700 for both analytes in sewage water. The repeatability and reproducibility were better than 8% and 17%, respectively. The developed methodology was used to study daily variations of fluoxetine and norfluoxetine in municipal sewage streams. Norfluoxetine has been detected for the first time in sewage water and a preliminary analysis gave average concentrations of 150 and 225 ng/L for norfluoxetine and fluoxetine, respectively.

Rethinking the urban water management of Copenhagen

Copenhagen currently relies on imported groundwater for its drinking water supply, but must become less reliant on external resources in future. A set of 9 scenarios for future water supply and waste water management are developed with the aim of making Copenhagen’s water supply entirely self sufficient. The scenarios are based on an analysis of current and past societal perceptions, mega trends and a catalogue of world’s best practice in urban water management. An initial screening of the scenarios is conducted by comparing them with a reference scenario (the current water supply) for the most important criteria. Perceptions, mega trends and evaluation criteria were identified by a stakeholder workshop. The scenarios that appear most promising are: central recirculation delivering water from a desalination and recycled grey water plant; a green city that relies on rainwater for supply and wastewater is separated and treated locally; a market driven water supply delivering various qualities of water and having separating sewage streams; and a local technological society where high tech treatment is used to produce and treat water within a neighbourhood.

Rethinking the urban water management of Copenhagen

Copenhagen currently relies on imported groundwater for its drinking water supply, but must become less reliant on external resources in future. A set of 9 scenarios for future water supply and waste water management are developed with the aim of making Copenhagen’s water supply entirely self sufficient. The scenarios are based on an analysis of current and past societal perceptions, mega trends and a catalogue of world’s best practice in urban water management. An initial screening of the scenarios is conducted by comparing them with a reference scenario (the current water supply) for the most important criteria. Perceptions, mega trends and evaluation criteria were identified by a stakeholder workshop. The scenarios that appear most promising are: central recirculation delivering water from a desalination and recycled grey water plant; a green city that relies on rainwater for supply and wastewater is separated and treated locally; a market driven water supply delivering various qualities of water and having separating sewage streams; and a local technological society where high tech treatment is used to produce and treat water within a neighbourhood.

A high rate clarifier for load levelling in sewerage systems

The combining of chemically assisted clarification with a proprietary physical separation technology has led to a high rate process for clarifying flocculated sewage and other waste streams. This hybrid physico-chemical system, known as the CDS Fine Solids Separation (FSS) System, was developed over a two year period within a sewage treatment plant environment. This paper summarises the results of a recent field trial of the system with a Victorian water authority which experiences heavy loading of sewers in a coastal town during holiday periods. The trial sought to evaluate the FSS as a tool for smoothing the load on the 11 km long sewer to the sewage treatment plant (STP). The FSS system could possibly enable the costly augmentation of the sewer to be deferred, particularly as the capacity of the existing sewer pipe is satisfactory for most of the year. Water quality parameters were determined for a range of flowrates and operational conditions over a two month period. Large reductions were achieved in TSS, TP, FC, turbidity and BOD5, with only minimal reductions in NH3 and TON. These results showed that the FSS could meet the authority's objectives for load levelling and would provide a 20-25% increase in effective sewer capacity. The data are also discussed in terms of possible use of the effluent from the FSS for water reuse applications.

Chemical analyses of water, sediment and biota in two small streams in southwest Germany

As a component of the VALIMAR project a comprehensive chemicalanalysis study was conducted in two small streams, the Korsch andthe Krahenbach, in southern Germany. The investigated pollutantswere heavy metals (HM), polycyclic aromatic hydrocarbons (PAHs),polychlorinated biphenyl's (PCBs) and a set of 33 pesticides.Samples from stream water, sewage treatment plant effluents,stream sediment and fish were analyzed. In the stream water, HMand PAHs showed slightly higher concentrations in the Korsch thanin the Krahenbach, whereas the pesticide concentrations (mainlyplant protective agents) were significantly higher in the Korschthan in the Krahenbach. Because of their similar occurrence andconcentrations in the Korsch water and in the sewage treatmentplant effluent, it appears that most of the pesticides wereintroduced into the river via the sewage treatment plant. Only inthe cases of terbuthylazine, triallate, chlorfenvinfos,metazachlor and mecoprop were the occurrence and concentrationsin the Korsch higher suggesting that run-off was the mostimportant route for these five compounds in this stream. The sediments of the two streams clearly differed in terms ofpollutant concentration. Polycyclic aromatic hydrocarbons, PCBsand HM were found in slightly higher concentrations in the Korschthan in the Krahenbach whereas pesticide concentrations weresignificantly higher in the Korsch. Results of each samplingdemonstrated extreme variations, due to frequent high-watersituations that led to high turnover and wash out of thesediment. In the sediment samples, most of the detected compoundswere more lipophilic than were those detected in water. Brown trout (Salmo trutta f. fario) and loach (Barbatulabarbatula) were sampled directly from the natural streams, from astream water fed bypass exposure system, and from a controlsystem in the laboratory. In the case of PAHs, PCBs andpesticides, concentrations were higher in fish exposed to theKorsch water than to the Krahenbach water. Heavy metals did notdifferentiate between the two streams. Polychlorinated biphenylsand pesticides showed higher concentrations in fish from thefield, which can be explained by longer exposure periods. Incontrast, PAHs showed the lowest concentrations under fieldconditions. Polycyclic aromatic hydrocarbons were possiblydisplaced by other compounds of high concentration. The pesticidepatterns in trout were quite similar in the different exposuretypes with primarily lindane, PCP and trifluraline contributingto these pattern changes. In loach, larger variations in allcontaminant concentrations were found but the same threecompounds also contributed most to the observed pattern changes. The analytical results were compared with various internationalobjective values for a good water quality as well as with valuesfrom other studies concerning the pollutant concentrations ofsediment and fish. All collected chemical data form a basis forthe biomarker investigations conducted by the other participantsof the VALIMAR project in order to find correlations betweenbiomarker responses and chemical pollution data of the twostreams.

Removal of Phosphate from Sewage as Amorphous Calcium Phosphate

This paper discusses the progress of laboratory scale and a larger pilot plant campaign directed at evaluating a new process for the removal and recovery of phosphate from municipal sewage (after secondary treatment) and certain industrial waste streams. The laboratory scale experiments (conducted at flow rates up to 75 l hr−1) on real sewage (total P around 10 mg l−1) and on a variety of simulated industrial and sewage streams (total P up to 160 mg l−1) were very successful in removing phosphorus to >98%, and produced a phosphate containing ‘product’ containing up to 18% elemental P (i.e. around 80% Ca3(PO4)2), and some of these laboratory scale tests are described in detail. However, when tested in the field with real sewage (flow rate 2 000 1 hr−1) the overall results were disappointing. Although phosphorus removal was excellent and achieved expectations (>95% removal of P from the sewage stream), the phosphate levels in the ‘product’ were far below those achieved in the laboratory work. This had dramatic effects on reagent utilisation and negative impact on the economic evaluation of the project. Also, despite general similarities between the process design and equipment used in both the laboratory scale and pilot plant equipment, during the pilot plant tests certain operational problems were encountered which were not anticipated from the laboratory scale work. The reasons for the discrepancies between the results obtained from laboratory and field experience are discussed with reference to a number of factors including: (1) functional differences in certain equipment (i.e. filter units), and differences in physical scaling factors between laboratory and pilot plant operations, (2) the effect on field operations of unforeseen components in real effluents specifically high bicarbonate levels and the presence of propionic acid, and, (3) inadequate flexibility in the construction of the pilot plant which precluded easy changes to plant configuration and introduction of new equipment. The pilot plant used in this work was built in a very robust manner, which is unsuitable for an experimental facility and better suited for construction of plant to continuously demonstrate an already proven process.

A non-fouling optical interface for environmental measurements

Transparent windows used to perform optical measurements in `difficult' samples such as natural waters in the environment and sewage streams in treatment plant inevitably become coated with chemically and/or biologically deposited films. These usually dominate the instrument's performance and reliability. We describe here a windowless measurement configuration, which avoids this fouling by supporting the water sample from below on an air bubble. By controlling the air pressure in the bubble with a fast pressure-modulator and feedback controller, the air-water meniscus' curvature is stabilized, and serves as a reliable optical interface to the liquid medium. Round menisci up to 8 mm in diameter have been stably controlled, with electronically regulated curvature. By periodically purging the bubble with air, long-term measurements of scattering and long-path absorption are possible, substantially free from fouling problems.

Improved Biological Phosphorus Removal Resulting from the Enrichment of Reactor Feed with Fermentation Products

Research in South Africa has highlighted the dependence of biological phosphate removal mechanisms on the presence of certain minimum concentrations of some readily biodegradable materials including interalia volatile fatty acids. Successful generation of these compounds has been achieved at recently commissioned facilities at three of Johannesburg' activated sludge plants. Elutriation of the volatile fatty acids from the sludge was achieved by recycling sludge to the influent sewage stream. Significant improvements in phosphate removal were observed, thus reducing the demand for chemical dosing to achieve the phosphate standard. In this paper the effect of altering the feed sewage characteristics on biological phosphorus removal is discussed.