Activated Sludge Operation Research Articles

Experimental support for a sustainable treatment strategy of acrylic fiber dyeing wastewater

AbstractThe study intended to devise a sustainable treatment scheme for acrylic fiber dyeing process effluents, which significantly differ from other textile plant wastewaters. The necessary experimental support was generated from a set of tests conducted on the wastewater of a plant operation, focused solely on acrylic fiber dyeing. Related experiments involved effluent characterization, biological treatability, and chemical settling/oxidation performed on raw and bio‐treated effluent, as pre‐treatment and/or polishing steps. A total COD level of 910 mg/L with a 70% soluble ratio, low total N and P contents below 10 mg/L, a detergent content of 50 mg/L and a dark/black color of 1150 Pt‐Co unit defined the average properties of the raw plant effluent. Experimental support indicated that activated sludge operation at a sludge age level above 25 d, remained insufficient as it could only provide an effluent with a soluble COD level above 150 mg/L, a biomass escape in the range of 40 to 100 mg/L and with an intense dark color. A similar experimental template, including chemical settling, chemical oxidation by NaOCl and combination of the two processes, was tested as pre‐treatment and a polishing step after biological treatment. Pre‐treatment, although with some benefit to remove toxic and inhibitory compounds, proved to be highly costly, due to excessive chemical usage and sludge generation for a sustainable, cost‐effective approach. The sequence of chemical oxidation and settling steps implemented as a polishing stage was quite effective as it secured complete color removal, a major source of concern for the selected wastewater and also, it reduced COD down to 60 mg/L, a level significantly below the residual COD threshold for biological treatment. This approach, although case‐specific for this study, provided a scientific and general perspective for similar work.

Didecyldimethylammonium Chloride- and Polyhexamethylene Guanidine-Resistant Bacteria Isolated from Fecal Sludge and Their Potential Use in Biological Products for the Detoxification of Biocide-Contaminated Wastewater Prior to Conventional Biological Treatment.

Simple SummaryEvery year, more than a million tons of fecal sludge (FS) containing biocides based on quaternary ammonium compounds and guanidine derivatives, which are widely used for FS deodorization and control of microbial activity, are generated in the environmentally safe toilet complexes of Russian Railways trains. Higher disposal costs for such biocide-contaminated FS due to activated sludge toxicity increases pressure on sanitary equipment servicing companies («Ecotol Service» LLC) to more efficiently discharge FS to wastewater treatment plants. In this work, we have developed a new environmentally friendly approach to reducing the toxicity of FS, based on the use of biological products from biocide-resistant bacterial strains isolated from FS. Our approach has proven to be effective in a series of FS biodegradation experiments, biological oxygen demand tests, and a newly developed disk-diffusion bioassay.Toxic shock caused by the discharge of biocide-contaminated fecal sludge (FS) from chemical toilets to conventional wastewater treatment plants (WWTP) can be a major problem in activated sludge operation. It is necessary to develop new environmental approaches to mitigate the toxicity of biocides in order to avoid degrading the performance of WWTP. “Latrina”, a chemical toilet additive containing didecyldimethylammonium chloride and polyhexamethylene guanidine, is widely used in environmentally safe toilet complexes (ESTC) on Russian railway trains to deodorize FS and control microbial activity. In this work, seven biocide-resistant bacterial strains were isolated and identified from the FS of ESTC. The values of the minimum inhibitory and bactericidal concentrations of biocides for the isolated strains were 4.5–10 times higher than for the collection microorganisms. The bacterium Alcaligenes faecalis DOS7 was found to be particularly resistant to “Latrina”, the minimum inhibitory concentration of which was almost 30 times higher than recommended for ESTC. Biological products based on isolated bacterial strains proved to be effective for FS biodegradation under both aerobic and anaerobic conditions. The results of the biochemical oxygen demand test and the newly developed disk-diffusion bioassay confirmed that isolated strains contribute to reducing toxicity of biocidal agents in FS. Hyper-resistance, non-pathogenicity, and potential plant growth-promoting ability make A. faecalis DOS7 promising for use in various biological products for wastewater treatment and bioremediation of soils contaminated with biocides, as well as in agriculture to increase plant productivity.

Candidatus Kaistella beijingensis sp. nov., Isolated from a Municipal Wastewater Treatment Plant, Is Involved in Sludge Foaming.

Biological foaming (or biofoaming) is a frequently occurring problem in wastewater treatment plants (WWTPs) and is attributed to the overwhelming growth of filamentous bulking and foaming bacteria (BFB). Biological foaming has been intensively investigated, with BFB like Microthrix and Skermania having been identified from WWTPs and implicated in foaming. Nevertheless, studies are still needed to improve our understanding of the microbial diversity of WWTP biofoams and how microbial activities contribute to foaming. In this study, sludge foaming at the Qinghe WWTP of China was monitored, and sludge foams were investigated using culture-dependent and culture-independent microbiological methods. The foam microbiomes exhibited high abundances of Skermania, Mycobacterium, Flavobacteriales, and Kaistella. A previously unknown bacterium, Candidatus Kaistella beijingensis, was cultivated from foams, its genome was sequenced, and it was phenotypically characterized. Ca. K. beijingensis exhibits hydrophobic cell surfaces, produces extracellular polymeric substances (EPS), and metabolizes lipids. Ca. K. beijingensis abundances were proportional to EPS levels in foams. Several proteins encoded by the Ca. K. beijingensis genome were identified from EPS that was extracted from sludge foams. Ca. K. beijingensis populations accounted for 4 to 6% of the total bacterial populations in sludge foam samples within the Qinghe WWTP, although their abundances were higher in spring than in other seasons. Cooccurrence analysis indicated that Ca. K. beijingensis was not a core node among the WWTP community network, but its abundances were negatively correlated with those of the well-studied BFB Skermania piniformis among cross-season Qinghe WWTP communities. IMPORTANCE Biological foaming, also known as scumming, is a sludge separation problem that has become the subject of major concern for long-term stable activated sludge operation in decades. Biological foaming was considered induced by foaming bacteria. However, the occurrence and deterioration of foaming in many WWTPs are still not completely understood. Cultivation and characterization of the enriched bacteria in foaming are critical to understand their genetic, physiological, phylogenetic, and ecological traits, as well as to improve the understanding of their relationships with foaming and performance of WWTPs.

Fate and toxicity of melamine in activated sludge treatment systems after a long-term sludge adaptation

Melamine is a nitrogen-rich (67% nitrogen by mass) heterocyclic aromatic compound that could significantly increase effluent total nitrogen concentrations. In this study, we investigated the degradation of melamine and its impact on activated sludge operations by employing two common activated sludge processes, namely the Modified Ludzack-Ettinger (MLE) process and the continuous stirred tank reactor (CSTR) process. Melamine was dosed continuously from day 125 in both activated sludge treatment systems at an influent concentration of 3 mg/L for about 100 days. Even after such a long period of sludge adaptation, melamine appeared not to be easily biodegradable. The average melamine removal efficiencies in the CSTR and MLE systems were 14 ± 10% and 20 ± 15%, respectively. There was no significant difference in melamine removal between the two different activated sludge processes. The long-term input of melamine resulted in a decrease in the nitrifying bacterial activities (by 82 ± 8%) and population in both systems. Short-term microtiter assay results also showed that melamine reduced activated sludge growth by 80% when supplied at a concentration of 75.6 mg/L. These results suggest that sludge adaptation plays a minimal role in melamine degradation, as the enzymes responsible for hydrolytic deamination of melamine in activated sludge are not easily induced. The insignificant biodegradation of melamine is also attributed to bacterial growth inhibition under long-term dosing conditions with melamine, resulting in a significant decrease in effluent water quality.

Activated Sludge Operation in the Extreme Conditions of MLSS, TDS, and Temperature

Activated Sludge Operation in the Extreme Conditions of MLSS, TDS, and Temperature

Converting BOD to Nitrification/Denitrification in Same Reactor While Maintaining Capacity

Converting BOD to Nitrification/Denitrification in Same Reactor While Maintaining CapacityThe Orange County Sanitation District (OCSD) modified their activated sludge operation from biochemical oxygen demand (BOD) to nitrification-denitrification (NDN) mode to reduce ammonia discharged and sent to the Groundwater Replenishment System (GWRS) operated by Orange County Water District. Full scale verification tests were conducted following conversion to NDN. The conversion to NDN was...Author(s)J.B. NeethlingBruce WilleyAdam NicholsMichelle HetheringtonDave HeinzRon WadeWendy SevenandtSourceProceedings of the Water Environment FederationSubjectSession 103: Developments in Nitrogen RemovalDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jan, 2011ISSN1938-6478SICI1938-6478(20110101)2011:8L.6627;1-DOI10.2175/193864711802793317Volume / Issue2011 / 8Content sourceWEFTECFirst / last page(s)6627 - 6637Copyright2011Word count130Subject keywordsNitrification-DenitrificationSecondary TreatmentConvert BOD to NDN

Xenobiotic substrate reduces yield of activated sludge in a continuous flow system

The biomass yield of a continuous flow activated sludge system varied when the system treated influent containing different compositions of biogenic and xenobiotic substrates. Both the biogenic substrate and a test xenobiotic 2,4-dichlorophenoxyacetic acid (2,4-D) were degraded at steady-state activated sludge operations. The true yields, determined from steady-state activated sludge treatment performances, were at the maximum and the minimum when the activated sludge treated the influent of sole biogenic substrate and sole 2,4-D, respectively. The minimum yield was 56% of the maximum. Yield reduction between the maximum and the minimum was proportional to the concentration of 2,4-D in the influent. This trend of yield reduction suited a model that describes the metabolic uncoupling effect of 2,4-D on the sludge’s degradation of the substrates. The model function variable was defined as the ratio of 2,4-D to biogenic COD concentrations in the influent.

Aerobic granule formation in a sequencing batch reactor treating newsprint effluent under low phosphate conditions

Pulp and paper mills are under increasing pressure to minimize the discharge of phosphate to receiving waters. We investigated the operation of two laboratory sequencing batch reactors (SBR) under low phosphate conditions over a period of eight months. Performance characteristics in terms of COD and TSS removal were similar to the full-scale mill activated sludge operation, but the floc density and structure was improved. Sludge yield as a result of phosphate limitation was routinely lower than 0.15 kg/kg of COD. Aerobic granule formation was established in one of the SBRs by reducing the settling time from 30 min to 2 min and by increasing stirring shear force. Once established, the brown granules which were 1-2 mm in diameter were stable over five months of operation. Extracellular polymeric substance (EPS) analysis of the granules indicated a higher galactose content and lower mannose content than in conventional flocs. The granules generated more quorum sensing compound (acyl homoserine lactone) than conventional flocs, suggesting that quorum sensing could play a role in granule formation. When compared to the conventional SBR, the aerobic granule SBR performed at a higher organic loading, at faster settling velocity, and without filamentous bulking.

Biological solution to storm water?

Standard practice in Flanders is to limit the hydraulic capacity of sewage treatment works to 6Q14 (Q14= 1.7 dry weather flow Q(DWF)). A maximum of 3Q14 is treated biologically, while the excess flow undergoes only physical treatment in storm tanks. This practice has been challenged by a new high-flow activated sludge operation concept, consisting of the treatment of the full storm sewage flow in the biological train and of the use of the storm tanks as additional secondary clarifiers. After successful testing in two installations, 56 works of different sizes and types were switched to high-flow activated sludge operation from 1999 to 2002. This paper reports on progress and experiences gained since then. The analysis focuses on the parameters subject to regulatory discharge (BOD, COD, suspended solids, total nitrogen and total phosphorus) plus ammonia. Special attention is paid to the performance of the clarification and of the nitrification processes. The results indicate that high-flow biological treatment provides a substantial reduction in wet weather discharges while maintaining acceptable process operating conditions.

N-ViroTech® - a novel process for the treatment of nutrient limited wastewaters

As pulp and paper wastewaters are mostly deficient in nitrogen and phosphorus, historical practice has dictated that they cannot be effectively treated using microbiological processes without the addition of supplementary nutrients, such as urea and phosphoric acid. Supplementation is a difficult step to manage efficiently, requiring extensive post-treatment monitoring and some degree of overdosing to ensure sufficient nutrient availability under all conditions. As a result, treated wastewaters usually contain excess amounts of both nutrients, leading to potential impacts on the receiving waters such as eutrophication. N-ViroTech is a highly effective alternative treatment technology which overcomes this nutrient deficiency/excess paradox. The process relies on communities of nitrogen-fixing bacteria, which are able to directly fix nitrogen from the atmosphere, thus satisfying their cellular nitrogen requirements. The process relies on manipulation of growth conditions within the biological system to maintain a nitrogen-fixing population whilst achieving target wastewater treatment performance. The technology has significant advantages over conventional activated sludge operation, including: Improved environmental performance. Nutrient loadings in the final treated effluent for selected nitrogen and phosphorus species (particularly ammonium and orthophosphate) may be reduced by over 90% compared to conventional systems; Elimination of nitrogen supplementation, and minimisation of phosphorus supplementation, thus achieving significant chemical savings and resulting in between 25% and 35% savings in operational costs for a typical system; Self-regulation of nutrient requirements, as the bacteria only use as much nitrogen as they require, allowing for substantially less operator intervention and monitoring. This paper will summarise critical performance outcomes of the N-ViroTech process utilising results from laboratory-, pilot-scale and recent alpha-adopter, full-scale trials.

Partial nitrification activated sludge operation as an appropriate nitrogen removal scheme for the Mediterranean region

Wastewater Treatment Plants (WWTPs) operation under conventional fully nitrifying activated sludge BNR schemes, although favoured by the temperate climate conditions prevailing around the Mediterranean region, may prove quite inefficient in terms of both capital and O&M costs when recipient body characteristics do not pose similar requirements; especially more so, when treated effluents are intended for reuse in agriculture and nitrogen content may well serve as fertilizer. This paper presents some experimental evidence that single-reactor partial nitrification schemes, allowing for nitrogen removal to the extent needed under seasonally varying plant loading conditions and effluent quality requirements, and securing reliable and efficient plant operation, may be a more suitable alternative for similar cases.

排水処理設備“サターン”の操業経験

Chuetsu Pulp & Paper's Futatsuka Mill is located in the southern part of Takaoka City, Toyama Prefecture, rather peaceful area on the western side of the Shou River surrounded by the green farmlands where the Japanese Alps can be seen far away. Its main product being newsprint, The mill also produces printing paper, book paper, medium quality paper and bleached paper. The two paper machines, one 3, 800 min wide and the other 7, 300 mm, together produce 190, 000 tons of paper a year. 250 tons of TMP (thermo-mechanical pulp) and 360 tons of DIP (deinked pulp) are produced per day. KP (kraft pulp) is brought from Noumachi Mill in slush and lap. Some imported mechanical pulps is also mixed depending on the paper grades. We have two boilers and a steam turbine that generates 85% of the mill's required electricity.We have continued to reinforce our environmental protection facility in accordance with the transitions of the production facilities. As for our activated sludge operation, when environmental matters became an issue in 1973, we built three 75 kW surface aeration systems to dispose 6, 400 kg per day of highly concentrated BOD effluent from the former CGP (chemical groundwood pulp) production system. Later the CGP system was replaced with the TMP system and the DIP system was installed. The production increased yearly which lead to the instability of the activated sludge operation. The Saturn and the Sun Jetter was installed to cope with this problem.We would like to particularly focus on the operations of Saturn hereinafter.

Optimization and Control of Alternating Aerobic/Anoxic Activated Sludge Operation

Although first principles models of activated sludge waste water processes exist, e.g. the ASM1 model, these models have rarely been used in practice for control or optimization. One problem with such usage is the complexity of the models, and another is their accuracy. This paper discusses the use of a linearized version of the ASM1 model for control and optimization of an alternating aerobic/anoxic activated sludge system. The linear nature of the model facilitates its use for online calculations, and feedback is used to overcome problems of model accuracy.

High Rate Air Activated Sludge Operation at the City of Los Angeles Hyperion Wastewater Treatment Plant

The City of Los Angeles USA Hyperion Treatment Plant (HTP) implemented high rate air activated sludge operations in November 1989. Using this process, the secondary treatment organic loading (F/M) was increased from 0.5 to 1.0 kg BOD/kg MLVSS/day and the MCRT reduced from 3.1 days to 1.5 days, thereby enabling the secondary treated flow to be increased from 150 mgd to 200mgd (6.6 to 8.8 m3/s). Excellent secondary effluent quality (BOD5 = 15 mg/l, carbonaceous BOD5 = 6 mg/l, SS = 6 mg/l) is currently obtained using rectangular secondary clarifiers operated at surface overflow rates of 1,100 gal/day/ft2 (43 m3/m2/day) and low MLSS concentrations (950 mg/l). The enhanced biological phosphorus removal that was obtained when operating at a 3 day MCRT was eliminated in the change to high rate operation and struvite (MgNH4PO4(c)) build-up in the anaerobic digesters has been eliminated. Nocardia scum formation, with its odor generating potential and other associated operating problems, has also been eliminated by high rate operation.

Algorithm for Optimal Activated Sludge Operation

A method for determining the minimum cost operation of an activated sludge wastewater treatment plant is developed and applied to a plant in Erie County, New York. The plant includes an aerated grit chamber, two aeration basins, two secondary clarifiers, two solids contact clarifiers, a flotation thickener, sand-drying beds, centrifuge, an aerobic digester, two gravity sand filters, and chlorination-reaeration facilities. The complex method of constrained optimization is modified for discrete-valued variables and used with nonlinear cost and process equations to determine the minimum cost operation of the plant for a specified 12-month flow sequence. The results from the optimization are compared with actual operation of the plant.

Purification efficiency in aeration tanks with complete mixing and piston flow

The course of BOD removal from sewage by activated sludge can be described by a second order reaction equation. Equations are presented for prediction of the purification efficiency in aeration tanks with piston flow and complete mixing. Short circuiting, though it can be demonstrated by means of an inert substance in any complete-mixing aeration tank, has no unfavourable effect on BOD reduction because rates of BOD removal in a complete-mixing aeration tank are high enough fully to eliminate the effect of short circuiting. A rate constant in a complete-mixing system was found to be about seven times higher than in a system with piston flow. The possibility is discussed of using the second order reaction equation for all aerobic biological processes, as it describes very well not only activated sludge operation but also trickling filters performance and the course of BOD.

Minimal Solids Aeration Activated Sludge

Modifications of the activated sludge process were sought to allow for more rapid and economical treatment of high strength, biologically degradable, organic wastes. Complete mixing activated sludge systems were tested on a laboratory scale to observe their performance under high organic volumetric loadings and short solids retention times. The systems operated effectively under these conditions, with percentages of removal of soluble organic matter from solution approaching those of conventional activated sludge as long as the systems were maintained aerobically. This type of activated sludge operation, however, produced a larger volume of biological solids than conventional activated sludge. Consequently, investigations were made, and data is reported on the feasibility of using either moderate or extended solids aeration complete mixing activated sludge, chemical treatment, or an oxidation pond for treatment of the biological solids wasted from these highly loaded, highly wasted, complete mixing activated sludge systems.