Sludge Liquor Research Articles

Increased nitrogen removal in existing volumes at Sundet wastewater treatment plant, Växjö

Many wastewater treatment plants need to improve their nitrogen removal due to stricter requirements and increasing loads. This often means larger bioreactor volumes, which can be very expensive and is sometimes impossible if space is limited. Therefore, there is a need for compact hybrid solutions that can increase capacity within existing volumes. Two full-scale demonstration projects using moving bed biofilm reactor (MBBR) technology has proven to be an efficient way to treat nitrogen in existing volumes at Sundet wastewater treatment plant in Växjö. Increased nitrification and denitrification capacity in parts of the main stream were demonstrated through the Hybas™ process, a combination of MBBR and activated sludge using the integrated fixed-film activated sludge technology. The ANITA™ Mox process, using autotrophic N-removal through anaerobic ammonium oxidation (anammox), provided high nitrogen removal for the sludge liquor. Data collected on-site for over a year are analyzed and compared with the performance of conventional treatment systems. These two full-scale demonstration projects have been a successful learning experience in identifying and correcting both process and operational issues, which may not have arisen at pilot scale. The set objectives in terms of nitrogen removal were met for both processes and design modifications have been identified that will improve future operation at Sundet WWTP.

Inhibition effect of free ammonia and free nitrous acid on nitrite-oxidising bacteria during sludge liquor treatment: influence of feeding strategy

AbstractThe importance of feeding strategy for the long-term selective inhibition of nitrite-oxidising bacteria (NOB) was demonstrated by comparison of laboratory-scale bioreactors: Completely Stirred Tank Reactor (CSTR) and Sequencing Batch Reactor (SBR). Moreover, the effect of the change of reactor operation regime from CSTR to SBR was demonstrated. Sludge liquor containing ammonia nitrogen in a range of 970–1500 mg L−1 was the influent of the reactors. The experiments were performed at (23 ± 2)°C, with high concentration of dissolved oxygen (up to 8 mg L−1) and with unlimited sludge retention time. In the SBR, permanent restriction of NOB activity was achieved for more than 700 days by the strong inhibition effect of fluctuating concentrations of free ammonia and free nitrous acid during the operational cycles of SBR. In contrast, nitrite-oxidising bacteria were able to gradually adapt to the conditions prevailing in CSTR and produce nitrate although the concentration of free ammonia and free nitrous acid significantly exceeded inhibition limits for NOB activity in this system. Transferring the reactor operation regime from CSTR to SBR resulted in immediate and permanent inhibition of NOB activity in the reactor.

Improving products of anaerobic sludge digestion by microaeration

Biogas, digested sludge and sludge liquor are the main products of anaerobic sludge digestion. Each of the products is influenced significantly by specific conditions of the digestion process. Therefore, any upgrade of the digestion technology must be considered with regard to quality changes in all products. Microaeration is one of the methods used for the improvement of biogas quality. Recently, microaeration has been proved to be a relatively simple and highly efficient biological method of sulfide removal in the anaerobic digestion of biosolids, but little attention has been paid to comparing the quality of digested sludge and sludge liquor in the anaerobic and microaerobic digestion and that is why this paper primarily deals with this area of research. The results of the long-term monitoring of digested sludge quality and sludge liquor quality in the anaerobic and microaerobic digesters suggest that products of both technologies are comparable. However, there are several parameters in which the 'microaerobic' products have a significantly better quality such as: sulfide (68% lower) and soluble chemical oxygen demand (COD) (33% lower) concentrations in the sludge liquor and the lower foaming potential of the digested sludge.

Implications of sludge liquor addition for wastewater-based open pond cultivation of microalgae for biofuel generation and pollutant remediation

The growth improvement of microalgal strains in municipal secondary-treated wastewater by addition of nutrient-rich activated sludge centrate liquor was examined. Two strains (Chlorella luteoviridis and Parachlorella hussii) were tolerant to liquor, with addition of 25% liquor providing the best growth, biomass productivity and nutrient removal values. The capability of C. luteoviridis and P. hussii for full seasonal cultivation in a 150 L open pond in a temperate climate was studied, using the optimised secondary wastewater +25% liquor medium. Each strain was capable of growth all year including in autumn and winter but with strongest growth, productivity and remediation characteristics in the summer and spring. Both strains could maintain monoculture growth with no significant contamination or culture crash, demonstrating the robustness of these strains for wastewater cultivation in a northern European climate. Each strain could also be efficiently cultivated in a semi-continuous system for steady production of biomass and nutrient removal.

Using Hydrolyzed Sludge Liquor as the Substrate of Microbial Fuel Cell

Using Hydrolyzed Sludge Liquor as the Substrate of Microbial Fuel Cell

Pilot-scale experiment on thermally hydrolyzed sludge liquor anaerobic digestion using a mesophilic expanded granular sludge bed reactor

A pilot process of thermal hydrolysis combined with an expanded granular sludge bed reactor (EGSB) was carried out to evaluate pretreated sludge liquor into biogas conversion, process stability, and energy input/output balance. Approximately 25% of suspended solids of sludge were liquefied into aqueous phase during thermal hydrolysis pretreatment, which resulted in chemical oxygen demand (COD) concentration of 20.0 to 35.0 g/L. A mesophilic EGSB reactor was operated for 206 days treating pretreated liquor. Under an organic loading rate of 11.0 kg COD/(m(3)·d) and hydraulic retention time of 60 h, COD conversion efficiency was maintained at 63%. The energy from biogas provided 80% of that demand for heating pretreatment. Dewatered sludge after thermal hydrolysis could be incinerated with municipal solid waste in an industrial-scale incinerator. Total energy production from combined biogas anaerobic digestion and sludge incineration, treating 1.0 kg raw sludge with moisture content of 82%, was 2419 kJ. The energy demand of thermal hydrolysis pretreatment was 340 kJ.

Experimental investigation and modeling of innovative five-tank anaerobic-anoxic/oxic process

A five-tank anaerobic-anoxic/oxic (A2/O) activated sludge process was investigated as innovative configuration in the activated sludge process technologies which has advantage of save energy power, cost and enhance nitrogen and phosphorus removal whereas it does not need equipment for sludge and mixed liquor recycle and also it required small land for construction. The five-tank process achieved 89.1%±1.37%, 87.78%±1.15%, 73.62%±2.13%, and 83.78%±0.92% of chemical oxygen demand, NH4+–N, TN, and total phosphorus (TP) removal efficiencies, respectively, during a 16-month operation with the effluent meeting Chinese sewage discharge standard GB18918-Grade A. A computer program was built based on activated sludge model No. 2d for simulating the performance of each compartment in five-tank process. The difficulty of simulation is coming from the system operation condition where it is operated under unsteadily state condition in all its compartments .The results showed that the growth rate constant of autotrophic organisms was 2.4day−1 and yield coefficient was 0.14. According to simulation results, heterotrophic organism; phosphate accumulating organism, and autotrophic organism are decreased in the anaerobic compartments because of the lysis reaction. Then these organisms are increased in the aerobic compartments due to aerobic growth. The heterotrophic organism; phosphate accumulating organism; and autotrophic organism are increased in quantities by about 56.6%, 36.12% and 74.31% in compartment one due to change the operation condition from anaerobic to aerobic and decreased in quantities by about 20.21%, 44.18%, and 0.142% in the compartment three due to change from aerobic to anoxic. The total nitrifying species to total active biomass was fluctuated between 1–11.89% in the process reactor.

Performance of a hybrid activated sludge/biofilm process for wastewater treatment in a cold climate region: Influence of operating conditions

The main aim of the study was to investigate a hybrid MBBR process, mostly in terms of organic matter removal and nitrification, when operating with different values of the mixed liquor sludge retention time (SRT), and highlighting the influence of temperature on the process. Based on experience in practice it was hypothesized that nitrification could be maintained at far lower SRT's than in conventional activated sludge systems and with high organic loading rates applied. A field gathering campaign has been carried out on a hybrid activated sludge/biofilm. The obtained results highlighted that the pilot plant was capable to remove the organic matter at loading rates up to 3.00kgTCODm−3day−1, also showing very high nitrification activity. Ammonia uptake rate (AUR) batch test showed that biofilm nitrification activity increased when the mixed liquor SRT decreased. The final suggestion is that it is possible to run a hybrid reactor with low mixed liquor SRT values, as well as low temperatures, still having a high ammonium removal efficiency, since a large fraction of nitrification activity will take place in the biofilm.

Modeling and particular application of ASM2d model for describing organic matter and nutrient removal in a novel anaerobic-anoxic/oxic eight-phased system

An eight-phased AA/O process has advantages of saving energy power, cost, and enhancing nitrogen and phosphorus removal; it does not need equipment for sludge and mixed liquor recycle and also it required small land for construction. A computer program was built based on activated sludge model No. 2d (ASM2d) for simulating the performance of multi-tank AA/O activated sludge process in Wuxi campus, Southeast university. The difficulty of simulation is the system operation with unsteadily state condition. The results indicated that the growth rate constant of ammonia oxidizing bacteria was 1.4 day−1 and yield coefficient was 0.14. According to simulation, heterotrophic organism XH, phosphate accumulating organism XPAO, and ammonia oxidizing bacteria XAOB decreased in the anaerobic tanks because of the lysis reaction. Then the XH, XPAO, and XA increased in the aerobic tanks due to aerobic growth. The heterotrophic microorganism; phosphorus accumulating organism; and autotrophic bacteria concentrations increased in quantities by about 56, 36, and 74% in tank one due to changes in the environmental state condition from anaerobic to aerobic and decreased in quantities by about 20, 44, and 0.14% in the tank three due to changes in the environmental state condition from aerobic to anoxic. The ratio of total nitrifying species to total active biomass varied between 1 and 12% in multi-tank AA/O process. The multi-tank AA/O system achieved 89 ± 1.3%, 87.7 ± 1.1%, 73.6 ± 2.1%, and 83.7 ± 0.9% of chemical oxygen demand, NH4+ -N, TN, and total phosphorus (TP) removal efficiencies, respectively, during a six-month operation with the effluent meeting Chinese sewage discharge standard GB18918-Grade A.

Phosphorus recovery potential from a waste stream with high organic and nutrient contents via struvite precipitation

Recovery of and via struvite precipitation (SP) was evaluated from liquor of thermally pretreated waste activated sludge, containing high levels of nutrients (1500 mg and 650 mg ), organics (45.5 g COD/L) and suspended solids (3.5 g TSS/L), with reference to anaerobically digested sludge centrate. In a series of jar tests, the order of pH adjustment and chemical addition were first tested for the digested sludge centrate. The effects of MgCl2 and MgO, as Mg2+ sources, on SP were evaluated in both waste streams. Up to 80% of the dissolved was recovered using MgO (pH=9.2) from the pretreated sludge liquor and more than 86% of from the digested sludge centrate (pH=8.0–8.5) regardless of the Mg2+ source used. recovery from digested sludge centrate required the addition of alkali, Mg2+ source and , making the process less viable. The precipitates contained mostly struvite and some levels of Ca2+, Fe2+ and other Mg2+ phosphates. The levels of solids, inorganics and organics in the waste streams influenced SP, specifically struvite crystal formation and settleability in the pretreated sludge liquor, which suggests that the applicability of SP for nutrient recovery from complex waste streams requires case-by-case testing, and process optimization.

The Optimum Process for Nutrient Removal from Sludge Liquor at a Centralized Sludge Treatment Plant in Yokohama City, Japan

The Optimum Process for Nutrient Removal from Sludge Liquor at a Centralized Sludge Treatment Plant in Yokohama City, JapanYokohama City has the centralized sludge treatment centers where sludge is fed from wastewater treatment plants (WWTPs). This system enables to high efficiency; however, the problem of sludge liquor which contains high nutrient concentrations comes up during sludge treatment process. Sludge liquor was treated by a recycled nitrification/denitrification process at the old facility up to 2010. The...Author(s)Akira YoshidaTakayuki MotohashiMariko InukaiSourceProceedings of the Water Environment FederationDocument typeConference PaperPublisherWater Environment FederationPrint publication date Oct, 2013ISSN1938-6478DOI10.2175/193864713813686042Volume / Issue2013 / 12Content sourceWEFTECCopyright2013Word count160

Biological nutrient removal using a novel five-step continuous flow activated sludge process technology

An anaerobic-anoxic/oxic (AA/O) five-tank biological process called five-step continuous flow activated sludge process (FSCFASP) was developed to force the oscillation of organic matter and nutrient concentrations in process reactors. The run scheme and schematic diagram of FSCFASP was described. The run cycle was divided into two symmetrical half cycles with eight periods during each cycle. The duration of each period was established according to biological process requirements. The optimal running times of the periods were 90, 60, 60, 30, 90, 60,6 0 and 30 min at the HRT of 16 h, air/water ratio of 35% and SRT of 21 day at the temperature range of 19–23 °C. The optimized system achieved 88.09±1.43%, 90.33±2.9%, 68.83±5.34% and 87.67±2.9% of the chemical oxygen demand, NH4 + -N, TN, and TP removal efficiencies, respectively, during a 11-month operation with the effluent meeting the Chinese sewage discharge standard GB18918-2002 (1evel A). Simultaneous nitrification and denitrification phenomena were observed in the tank one which is important to reduce the quantity of aeration and the duration of a next anoxic state. Compared with other existing technologies, this system achieved high nitrogen and phosphorus removal without equipment of sludge and mixed liquor return. Thus, it is effective for reducing energy consumption.

Design Considerations for a Multiple-Reactor DEMON Process Treating Sludge Liquors from a Thermal Hydrolysis Anaerobic Digester

Design Considerations for a Multiple-Reactor DEMON Process Treating Sludge Liquors from a Thermal Hydrolysis Anaerobic DigesterThe DEMON treatment process is rapidly becoming an established technology for sidestream treatment due to its low energy use and no requirement for carbon addition to remove nitrogen completely through deammonification. A new filtrate treatment facility (FTF) based on the DEMON process and currently under design for the Blue Plains Advanced Wastewater Treatment Plant (AWTP) has several unique...Author(s)Andrew ShawPeter ThomsonBeverley StinsonSalil KharkarSudhir MurthyChris deBarbadilloNick PassarelliBernhard WettGeert NyhuisBlair WisdomSourceProceedings of the Water Environment FederationDocument typeConference PaperPublisherWater Environment FederationPrint publication date Jul, 2013ISSN1938-6478DOI10.2175/193864713813525428Volume / Issue2013 / 4Content sourceNutrient Removal and Recovery SymposiumCopyright2013Word count159

Application of Chemical Precipitation in Treating Ammonia Nitrogen from Excess Sludge Liquor

Removal effect of NH3-N by chemical precipitation process was studied in treating excess sludge liquor (the NH3-N concentration 600~1000mg/L) produced from a municipal wastewater treatment plant. MgSO4 and Na2HPO4 were used as the precipitants to investigate the influences of initial pH, reaction time and the precipitants dosage on the NH3-N removal effect as well as the concentration of residual TP. Results showed that with the initial pH of 11.0, reaction time of 10min, and the additional ratio of precipitants being Mg:N:P＝1.0:1.0:1.0, over 90% NH3-N removal efficiency was achieved which would significantly facilitate the subsequent biological treatment process.

Removal of organic micro-pollutants from solid waste landfill leachate in membrane bioreactor operated without excess sludge discharge

Two-stage membrane bioreactor (MBR) system was applied to the treatment of landfill leachate from a solid waste disposal site in Thailand. The first stage anoxic reactor was equipped with an inclined tube module for sludge separation. It was followed by an aerobic stage with a hollow fiber membrane module for solid liquid separation. Mixed liquor sludge from the aerobic reactor was re-circulated back to anoxic reactor in order to maintain constant mixed liquor suspended solids (MLSS) concentration in the aerobic reactor. The removal of micro-pollutants from landfill leachate along the treatment period of 300 days was monitored. The results indicated that two-stage MBRs could remove biochemical oxygen demand (BOD), chemical oxygen demand (COD) and NH(4)(+) by 97, 87 and 91% at steady operating condition. Meanwhile organic micro-pollutant removals were 50-76%. The removal efficiencies varied according to the hydrophobic characteristic of compounds but they were improved during long-term MBR operation without sludge discharge.

Application of a simple arsenic removal filter in a rural area of Bangladesh

A simple and low-cost household-based arsenic (As) removal filter (ARF) was tested under actual field conditions in a rural area of Bangladesh. The ARF consisted of a ceramic filter made of clay soil and rice bran collected on-site, iron netting and iron bacterial sludge liquor. Fifteen ARFs (14 shallow and one deep tubewells) were installed in three villages (five in each area) in the Khulna region (southwestern region of Bangladesh), and their performance was evaluated. More than 60% of ARFs produced effluent with As <50 μg/L (Bangladesh standard level). The effects of Fe and P on As removal were the same as in laboratory experiments. X-ray Absorption Fine Structure (XAFS) analysis showed the adsorption of primarily As(V), with lesser amounts of As(III). Continuous As removal performance was observed over 1 year of ARF use. By introducing a double ARF system, the As removal was significantly enhanced for the region with high As contamination levels. The ARF manufacturing cost was estimated to be US$4–5, which is low and affordable to the rural households of Bangladesh. The ARF, made of locally available materials, had a low cost and minimal maintenance and showed high user acceptance, satisfaction and sustained use.

Comparison and Analysis of Membrane Fouling between Flocculent Sludge Membrane Bioreactor and Granular Sludge Membrane Bioreactor

The goal of this study is to investigate the effect of inoculating granules on reducing membrane fouling. In order to evaluate the differences in performance between flocculent sludge and aerobic granular sludge in membrane reactors (MBRs), two reactors were run in parallel and various parameters related to membrane fouling were measured. The results indicated that specific resistance to the fouling layer was five times greater than that of mixed liquor sludge in the granular MBR. The floc sludge more easily formed a compact layer on the membrane surface, and increased membrane resistance. Specifically, the floc sludge had a higher moisture content, extracellular polymeric substances concentration, and negative surface charge. In contrast, aerobic granules could improve structural integrity and strength, which contributed to the preferable permeate performance. Therefore, inoculating aerobic granules in a MBR presents an effective method of reducing the membrane fouling associated with floc sludge the perspective of from the morphological characteristics of microbial aggregates.

Phosphorus Recovery from Wastewater—Expert Survey on Present Use and Future Potential

Today, a variety of different approaches to the recovery of phosphorus from wastewater, sludge, and sludge ash exist. These approaches differ basically by the origin of the used matter (wastewater, sludge liquor, fermented or nonfermented sludge ash) and the process (precipitation, wet-chemical extraction, and thermal treatment). To rate them according to their characteristics, the latter were phrased as hypotheses and subjected to an international expert survey. The survey showed that phosphorus recovery is expected to become an established process over the next 20 years in industrialized countries for economic reasons. A decisive aspect in this regard will be the quality of the produced fertilizer. Simple technologies such as the recovery from sludge liquor seem to be preferred. If sludge is incinerated, phosphorus recycling from ash then becomes more interesting and has to be considered. Phosphorus recovery and source-separating sanitation technologies are more appropriate for industrialized countries than for developing countries. Because the growing awareness of environmental issues will prevent sludge from being used agriculturally in an increasing number of countries in the next decade, the market potential for nutrient recovery technologies will increase in the immediate future.

Phosphorus Recovery from Urban Wastewater Treatment Plant Sludge Liquor by Ion Exchange

In this study phosphorus recovery from sludge liquor by ion exchange process was investigated. The efficiency of a commercially available anionic iron oxide resin was evaluated in batch and packed column tests using synthetic phosphorus solution and actual sludge liquor, taken from of an urban wastewater treatment plant (UWWTP). When phosphorus recovery from sludge liquor was investigated, experimental data fitted quite well Generalized Langmuir–Freundlich isotherm (R2 = 0.92 for the new resin and R2 = 0.96 for the regenerated resin); the maximum adsorption capacity being 14.2 and 14.4 mg P/g, respectively. The saturation of adsorption sites was not achieved also after 11.5 hours and 120 bed volumes, in column tests. When the reactor was operated with sludge liquor and the new resin, the saturation of packed bed was achieved after approximately 175 min and 31 bed volumes. The recovery efficiency of phosphorus during the regeneration step was as high as 95% (less than 13 bed volumes). According to the results achieved and the increasing cost of phosphorus production from conventional resources (yearly incremental cost 0.012 €/(kg · y)), its recovery from UWWTPs sludge liquor by the ion exchange process is expected to be really useful and beneficial for the following 10–15 years.

THE EFFECT OF IRON SALT ON ANAEROBIC DIGESTION AND PHOSPHATE RELEASE TO SLUDGE LIQUOR / GELEŽIES DRUSKOS ĮTAKA ANAEROBINIO DUMBLO PŪDYMO PROCESUI IR FOSFATŲ IŠSISKYRIMUI Į DUMBLO VANDENĮ

Iron salts are used at wastewater treatment plants (WWTPs) for several reasons: for removing chemical phosphorus, preventing from struvite formation and reducing the content of hydrogen sulfide (H2S) in biogas. Anaerobic digestion is a common scheme for sludge treatment due to producing biogas that could be used as biofuel. Laboratory analysis has been carried out using anaerobic digestion model W8 (Armfield Ltd, UK) to investigate any possible effect of adding FeCl3 on the anaerobic digestion of primary sludge (PS) and waste activated sludge (WAS) mixture as well as on releasing phosphates to digested sludge liquor. The obtained results showed that FeCl3 negatively impacted the anaerobic digestion process by reducing the volume of produced biogas. Fe-dosed sludge (max) produced 30% less biogas. Biogas production from un-dosed and Fe-dosed sludge (min) was similar to the average of 1.20 L/gVSfed. Biogas composition was not measured during the conducted experiments. Phosphorus content in sludge liquor increased at an average of 38% when digesting sludge without ferric chloride dosing. On the contrary, phosphate content in sludge liquor from digested Fe-dosed sludge decreased by approx. 80%. Santrauka Nuotekų valymo įrenginiuose geležies druskos naudojamos cheminiam fosforui šalinti, sieros vandeniliui biodujose mažinti ir struvito nuogulų formavimosi prevencijai. Tyrimai atlikti laboratorinėmis sąlygomis naudojant anaerobinio pūdymo modelį W8 (Armfield Ltd., Didžioji Britanija) ir pūdant pirminio perteklinio dumblo mišinį, į kurį buvo dedama geležies druskos, siekiant nustatyti geležies druskos naudojimo efektą anarobinio pūdymo procesui ir fosfatų išsiskyrimui į dumblo vandenį. Rezultatai parodė, kad pūdant dumblą be geležies druskos ir dedant geležies druskos minimalią dozę, susidarė vidutiniškai vienodi kiekiai biodujų (mL/gBSMtiekiam.), bet į pūdomą dumblą dedant maksimalią geležies dozę, biodujų išeiga vidutiniškai sumažėjo 30 %. Į pūdomą dumblą nededant geležies chlorido, fosfatų koncentracija dumblo vandenyje vidutiniškai padidėjo 38 %. Ir priešingai, geležies chlorido dozės fosfatų koncentraciją pūdyto dumblo vandenyje sumažino 80 %.