Reduce Sludge Production Research Articles

A Bibliometric Analysis of Sludge Research from 2000 to 2011

This study explores a bibliometric approach to quantitatively assessing current research trends on sludge, by using the related literature published between 2000 and 2011. The articles acquired from such literature were concentrated on the general analysis by publication type and language, characteristics of articles outputs, country, subject categories and the frequency of title-words used. Over the past 12 years, there had been a notable growth trend in publication outputs, along with more participation of countries/territories. An analysis of the title-words showed that wastewater treatment was still the most hot topic in sludge research and wastewater, heavy metal, waste water treatment and anaerobic digestion were recent major topics of sludge research. Besides, membrane bioreactor technology has been advancing rapidly around the world and became an ideal way to reduce sludge production in the wastewater treatment process.

Evaluation of sludge reduction by an environmentally friendly chemical uncoupler in a pilot-scale anaerobic/anoxic/oxic process

An environmentally friendly chemical, tetrakis(hydroxymethyl)phosphonium sulfate (THPS), was used as a metabolic uncoupler to reduce sludge production in a pilot-scale anaerobic/anoxic/oxic process. The results show that the addition of THPS (1.08-1.86mL/m(3) influent) in the sludge return section could reduce waste activated sludge by about 22.5%, and decrease the sludge yield by about 14.7% at the end of a run. At the same time, the addition of THPS slightly lowered the removal of chemical oxygen demand (COD), soluble COD and NH4 (+)-N, and slightly improved removal of total nitrogen. The effects of THPS addition on two characteristics of activated sludge in oxic tank are discussed in detail and the results suggest that the settleability of sludge was reduced by addition of THPS, while the specific oxygen uptake rate was increased. Molecular biology analysis shows that the addition of THPS had little effect on the microbial communities of sludge.

A free nitrous acid (FNA)-based technology for reducing sludge production

Sludge treatment and disposal is one of the major challenges for biological wastewater treatment plants and can represent up to 60% of their total operating costs. This study presents a novel strategy based on free nitrous acid (FNA or HNO2) treatment to achieve sludge reduction. Two sequencing batch reactors treating synthetic domestic wastewater were used, with one serving as an experimental reactor and the other as a control. In the experimental system, 50% of the excess sludge was exposed to FNA at 2.0 mg N/L for 24–42 h in an FNA treatment unit and then returned to the parent reactor. The sludge wastage flow from the experimental reactor was adjusted to obtain a similar mixed liquor suspended solids concentration to that in the control reactor, which was operated at a sludge retention time of 15 days. It was found that sludge production in the experimental system was 28% lower in comparison to the control. The addition of the FNA-treated sludge did not negatively affect the treatment performance and sludge properties of the experimental reactor, namely the organic carbon and nitrogen removal, nitrous oxide (N2O) emission and sludge settleability. Endogenous denitrification batch tests indicate that FNA-treated sludge is available as a carbon source for denitrification.

Biological sludge reduction during abattoir wastewater treatment process using a sequencing batch aerobic system

Excess sludge disposal during biological treatment of wastewater is subject to numerous constraints, including social, health and regulatory factors. To reduce the amount of excess sludge, coupled processes involving different biological technologies are currently under taken. This work presents a laboratory scale sequencing batch aerobic system included an anaerobic zone for biomass synchronization (SBAAS: sequencing batch aerobic anaerobic system). This system was adopted to reduce sludge production during abattoir wastewater (AW) treatment. The average chemical oxygen demand (COD) removal efficiency of 89% was obtained at a hydraulic retention time (HRT) and a sludge retention time (SRT) of 2 days and 15–20 days, respectively. The comparison of SBAAS performances with a conventional sequencing batch activated sludge system (SBASS) found that the observed biomass production yield (Y obs) were in the ranges of 0.26 and 0.7 g suspended solids g −1 COD removed, respectively. A significant reduction in the excess biomass production of 63% was observed by using the SBAAS. In fact, in the anaerobic zone microorganisms consume the intracellular stocks of energy by endogenous metabolism, which limits biosynthesis and accelerates sludge decay. The single strand conformation polymorphism (SSCP) method was used to study the dynamic and the diversity of bacterial communities. Results showed a significant change in the population structure by including the anaerobic stage in the process, and revealed clearly that the sludge production yield can be correlated with the bacterial communities present in the system.

Energy and Performance Comparison of Microbial Fuel Cell and Conventional Aeration Treating of Wastewater

Microbial fuel cell (MFC) technology provides a low cost alternative to conventional aerated wastewater treatment, however, there has been little comparison between MFC and aeration treatment using real wastewater as the substrate. This study attempts to directly compare the wastewater treatment efficiency and energy consumption and generation among three reactor systems-a traditional aeration process, a simple submerged MFC configuration, and a control reactor acting similar as natural lagoons. Results showed that all three systems were able to remove >90% of COD, but the aeration used shorter time (8 days) than the MFC (10 days) and control reactor (25 days). Compared to aeration, the MFC showed lower removal efficiency in high COD concentration, but much higher efficiency when the COD is low. Only the aeration system showed complete nitrification during the operation, reflected by completed ammonia removal and nitrate accumulation. Suspended solid measurements showed that MFC reduced sludge production by 52-82% as compared to aeration, and it also saved 100% of aeration energy. Furthermore, though not designed for high power generation, the MFC reactor showed a 0.3 Wh/g COD/L or 24 Wh/m3 (wastewater treated) net energy gain in electricity generation. These results demonstrate that MFC technology could be integrated into wastewater infrastructure to meet effluent quality and save operational cost.

Disintegration of Sludge by Sonication and Improvement of Methane Production Rates in Batch Anaerobic Digesters

AbstractSludge pretreatment prior to anaerobic digestion has been found to reduce sludge production in wastewater treatment. Sludge disintegration using physical, chemical, biological, or mechanical methods can increase biogas production and reduce sludge quantities. Ultrasonication is one of the most effective means of mechanical disintegration. This study aims to investigate ultrasonication as a means for solubilizing waste activated sludge (WAS) to enhance its digestability. Sonication was applied by the use of two different probes providing different powers and energies into the sludge after which the soluble chemical oxygen demand (sCOD) increases were measured. The samples were then digested anaerobically in 250 mL serum bottles for about 50 days. Along with the biogas measurements, the rate of methane production is calculated to be able to quantify the effect of pretreatment and compare the results between different applications. The results showed that with the increase of sonication power and sonication time, sCOD increased. An introduction of higher sonication energy made the sCOD rise sharply, however, this increase was not indefinite; it became gradually lower with the further increase of energy. The results indicated that specific methane production, specific methane yield, and the first order methane generation rate increased with increasing energy input.

Effects of sludge pretreatment on sludge reduction in a lab-scale anaerobic/anoxic/oxic system treating domestic wastewater

Excess sludge disposal is one of the serious challenges in biological wastewater treatment. Reduction of sludge production would be an ideal way to solve sludge- associated problems rather than the post-treatment of the sludge produced. In this study, a new wastewater treatment process combining anaerobic/anoxic/oxic system with thermochemical sludge pretreatment was tested in a labo- ratory scale experiment. In this study, the effects of the sludge pretreatment on the excess sludge production in anaerobic/anoxic/oxic were investigated. The system was operated in two Runs (1 and 2). In Run 1, the system was operated as a reference and in Run 2, a part of the mixed liquid was pretreated thermochemically and was returned to the bioreactor. The average solubilization efficiency of pretreated sludge was found to be about 35 % during the study period of 220 days. Sludge production rate in Run 2 was less than that in Run 1 by about 52 %. Total phos- phorous was removed by enhanced biological phosphorous removal with the removal efficiency of 83-87 % and 81-83 % for Run 1 and Run 2, respectively. Total nitrogen removal in Run 2 (79-82 %) was slightly higher than that in Run 1 (68-75 %). The mixed liquor suspended solids/ mixed liquor volatile suspended solids ratio was identical after both runs in the range 78-83 %. The effluent water qualities were not significantly affected when operated with thermochemical pretreatment at pH 11 and 60 C for 3 h during 7 months. From the present study it is concluded that thermochemical sludge pretreatment of anaerobic/anoxic/ oxic process plays an important role in reduction of sludge production.

Utilization of Energy and Growth of Aquatic Worms during the Process of Sludge Reduction by Aquatic Worms

In the research, the dissolved oxygen, energy efficiency index, growth of aquatic worms and sludge reduction were determined and analyzed. The energy use of aeration and the growth of aquatic worms were investigated during the process of in-situ sludge reduction by aquatic worms. For the wastewater treatment system adding with adequate aquatic worms, the power consumption was not increased and the utilization rate of oxygen was improved. The growth of aquatic worms well fitted DoseResp function and the sludge production was reduced evidently. Results indicate that the wastewater treatment adding with aquatic worms utilizes aeration energy sufficiently and reduces sludge production effectively.

Reduction of the sludge production in a sequencing batch reactor by addition of chlorine dioxide: Influence on the process performance

Costs reduction in the activated sludge process in municipal wastewater treatment plants (MWWTPs) has nowadays become of paramount important due to the current economic situation. One of the saving measures that are being currently studied is the reduction of sludge production. In this work, the influence of the addition of chlorine dioxide to a sequencing batch reactor (SBR) on the sludge production and on the process performance has been studied. After preliminary jar-tests to select the ClO2 concentration range to be studied, two series of experiences were carried out. In the first series of experiments two laboratory SBRs were operated in parallel to test the effect of three different ClO2 doses. In the second one, three laboratory SBRs were operated in parallel to go on studying the influence of the chlorine dioxide addition on the SBRs performance and to compare two different dosing strategies (directly to the reactor and mixing the oxidant with a part of the sludge in a separated tank). SBRs treated simulated municipal wastewater and they were operated with the same operating strategy. Results showed that doses of 5 and 10mg ClO2/gTSS entailed severe deterioration of the biological process, meanwhile the dose of 2mg ClO2/gTSS hardly decreased the COD removal performance, implying a reduction of sludge production of 20.2%. An increase of the dose up to 2.5mg ClO2/gTSS increased the reduction of the sludge production up to 43.4%, when the oxidant was added directly to the reactor in the anoxic reaction phase.

Comparison between ozonation and the OSA process: analysis of excess sludge reduction and biomass activity in two different pilot plants

The excess biomass produced during biological treatment of municipal wastewater represents a major issue worldwide, as its disposal implies environmental, economic and social impacts. Therefore, there has been a growing interest in developing technologies to reduce sludge production. The main proposed strategies can be categorized according to the place inside the wastewater treatment plant (WWTP) where the reduction takes place. In particular, sludge minimization can be achieved in the wastewater line as well as in the sludge line. This paper presents the results of two pilot scale systems, to evaluate their feasibility for sludge reduction and to understand their effect on biomass activity: (1) a pilot plant with an ozone contactor in the return activated sludge (RAS) stream for the exposition of sludge to a low ozone dosage; and (2) an oxic-settling-anaerobic (OSA) process with high retention time in the anaerobic sludge holding tank have been studied. The results showed that both technologies enabled significant excess sludge reduction but produced a slight decrease of biomass respiratory activity.

Performance evaluation of an integrated photo-Fenton – Electrocoagulation process applied to pollutant removal from tannery effluent in batch system

The treatment of tannery industrial effluent (TIE) by integrating the widely used photo-Fenton and electrocoagulation (EC) processes was investigated. The optimization of the photo-Fenton process by using solar irradiation was made performing a full 33 factorial experimental design. An irradiation time of 120min for the photo-Fenton reaction was more favorable to pollutant removal in acidic medium using Fe2+ concentrations ranging from 0.4 to 0.5gL−1 and H2O2 concentrations ranging from 15 to 30gL−1. Nonetheless, a reduction in sludge production and a minimum residual content of hydrogen peroxide were attained within 540min of irradiation time, with 0.4gL−1 Fe2+ and 15gL−1 H2O2 initial concentrations, with almost the same efficiency of COD, color, and turbidity removal obtained under the optimal experimental conditions. When the pretreated TIE samples were submitted to an EC process, the results of inorganic pollutants removal were better than with the conventional method (use of a combination of filtration, chemical coagulation, and sedimentation processes). In addition, the application of the integrated photo-Fenton and EC process for TIE treatment is cheaper than the conventional one. All the results showed that the integrated photo-Fenton and EC process could be applied as an efficient low-cost alternative treatment for the removal of organic and inorganic pollutants from tannery industrial effluent with a low environmental impact.

Nitrate reduction by organotrophic Anammox bacteria in a nitritation/anammox granular sludge and a moving bed biofilm reactor

The effects of volatile fatty acids (VFAs) on nitrogen removal and microbial community structure in nitritation/anammox process were compared within a granular sludge reactor and a moving bed biofilm reactor. Nitrate productions in both systems were lower by 40–68% in comparison with expected nitrate production. Expected sludge production on VFAs was estimated to be 67–77% higher if heterotrophs were the main acetate degraders suggesting that Anammox bacteria used its organotrophic capability and successfully competed with general heterotrophs for organic carbon, which led to a reduced sludge production. FISH measurements showed a population consisting of mainly Anammox and AOB in both reactors and oxygen uptake rate (OUR) tests also confirmed that flocculent biomass consisted of a minor proportion of heterotrophs with a large proportion of AOBs. The dominant Anammox bacterium was Candidatus “Brocadia fulgida” with a minor fraction of Candidatus “Anammoxoglobus propionicus”, both known to be capable of oxidizing VFAs.

Enhanced nitrogen removal in a wastewater treatment process characterized by carbon source manipulation with biological adsorption and sludge hydrolysis

An innovative adsorption/nitrification/denitrification/sludge-hydrolysis wastewater treatment process (ENRS) characterized by carbon source manipulation with a biological adsorption unit and a sludge hydrolysis unit was developed to enhance nitrogen removal and reduce sludge production for municipal wastewater treatment. The system presented good performance in pollutants removal, yielding the effluent with average COD, NH4+-N, TN and TP of 48.5, 0.6, 13.2 and 1.0mg/L, respectively. Sixty percent of the total carbon source in the influent was concentrated and separated by the quick adsorption of activated sludge, providing the possibilities of reusing waste carbon source in the denitrification tank and accumulating nitrobacteria in the nitrification tank. Low temperature of 6–15°C and high hydraulic loading rate of 3.0–15.0m3/d did not affect NH4+-N removal performance, yielding the NH4+-N of lower 1.0mg/L in the effluent. Furthermore, 50% of the residual sludge in the ENRS system could be transformed into soluble COD (SCOD) by alkaline thermal hydrolysis with temperature of 60°C and pH of 11, and the hydrolyzed carbon could completely substitute methanol as a good quality carbon to support high efficient denitrification.

Potential use of Uncouplers to Reduce Activated Sludge Production

Activated sludge is one of the main processes used for wastewater treatment. Activated sludge is associated with the production of excess sludge, commonly referred to as wasted activated sludge (WAS). The handling and disposal of this sludge accounts for more than 40% of operational costs in a typical waste water treatment plant (WWTP). There were 26,000 tonnes of dry sludge produced in Melbourne during the years 2009-2010 according to the annual report by Melbourne Water and $43 million has been invested in Western Treatment Plant to improve the sludge treatment. 5840 tonnes of the sludge was collected and sent to a landfill for disposal, at a total cost of $494,210. Therefore, attention has been given to modifications to the activated sludge process with potential for minimization of excess sludge. One possible modification is the use of metabolic uncouplers, chemicals that can uncouple the energy transfer in cells and ultimately reduce activated sludge yield. The aim of this research was to evaluate two uncouplers, 3, 3’, 4’, 5-tetrachlorosalicylanilide (TCS) and para-nitrophenol (PNP also known as 4-nitrophnol or 4-NP) for their potential for reducing sludge production. A series of laboratory scale batch tests were carried out. The results obtained showed that TCS, at a concentration of 0.8 mg/L, can reduce activated sludge production by 45%, with little effect on COD removal. In comparison, a high concentration of 30 mg/L PNP was required to reduce sludge production by 30% but little effect on COD removal was observed.

Excess activated sludge reduction by using electromagnets and ferrite particles

AbstractEvery year, the ratio of the sewarage treatment to population is increasing in Japan. Expansion in sewer networks is leading to the production of excess sludge which is one of the major problems in wastewater treatment plants. There are several approaches to treat the excess activated sludge. A new approach is to reduce excess sludge production by using magneto‐ferrite treatment. The Suzuki Lab of Akita University, Japan, is working on this project. We have succeeded in using magneto‐ferrite treatment in the lab scale to reduce sludge production. Ferrite particles and magnets are used in this method. Ferrite particles are nontoxic and safe for biological systems. They can be easily separated from the sludge by using magnets. However, the movement of the ferrite particles in the sludge is controlled by permanent magnets which can be made more effective by changing to electromagnets. In this paper, we describe an approach to use electromagnets instead of permanent magnets. Electromagnets can be controlled easily with an AC power supply. The results of our experiments have shown a good possibility for reduction of excess sludge. © 2011 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Low temperature thermo-chemical pretreatment of dairy waste activated sludge for anaerobic digestion process

An investigation into the influence of low temperature thermo-chemical pretreatment on sludge reduction in a semi-continuous anaerobic reactor was performed. Firstly, effect of sludge pretreatment was evaluated by COD solubilization, suspended solids reduction and biogas production. At optimized condition (60°C with pH 12), COD solubilization, suspended solids, reduction and biogas production was 23%, 22% and 51% higher than the control, respectively. Secondly, semi-continuous process performance was studied in a lab-scale semi-continuous anaerobic reactor (5L), with 4L working volume. With three operated SRTs, the SRT of 15days was found to be most appropriate for economic operation of the reactor. Combining pretreatment with anaerobic digestion led to 80.5%, 117% and 90.4% of TS, SS and VS reduction respectively, with an improvement of 103% in biogas production. Thus, low temperature thermo-chemical can play an important role in reducing sludge production.

A full scale worm reactor for efficient sludge reduction by predation in a wastewater treatment plant

Sludge predation can be an effective solution to reduce sludge production at a wastewater treatment plant. Oligochaete worms are the natural consumers of biomass in benthic layers in ecosystems. In this study the results of secondary sludge degradation by the aquatic Oligochaete worm Aulophorus furcatus in a 125 m 3 reactor and further sludge conversion in an anaerobic tank are presented. The system was operated over a period of 4 years at WWTP Wolvega, the Netherlands and was fed with secondary sludge from a low loaded activated sludge process. It was possible to maintain a stable and active population of the aquatic worm species A. furcatus during the full period. Under optimal conditions a sludge conversion of 150–200 kg TSS/d or 1.2–1.6 kg TSS/m 3/d was established in the worm reactor. The worms grew as a biofilm on carrier material in the reactor. The surface specific conversion rate reached 140–180 g TSS/m 2d and the worm biomass specific conversion rate was 0.5–1 g TSS sludge/g dry weight worms per day. The sludge reduction under optimal conditions in the worm reactor was 30–40%. The degradation by worms was an order of magnitude larger than the endogenous conversion rate of the secondary sludge. Effluent sludge from the worm reactor was stored in an anaerobic tank where methanogenic processes became apparent. It appeared that besides reducing the sludge amount, the worms’ activity increased anaerobic digestibility, allowing for future optimisation of the total system by maximising sludge reduction and methane formation. In the whole system it was possible to reduce the amount of sludge by at least 65% on TSS basis. This is a much better total conversion than reported for anaerobic biodegradability of secondary sludge of 20–30% efficiency in terms of TSS reduction.

Evaluation of a new model for the reduction of excess sludge production by ozonation of return activated sludge: what solids COD fraction is affected?

This paper aims at clarifying the effect of ozone on the RAS solids to model activated sludge systems equipped with RAS-ozonation processes for the reduction of sludge production. A common hypothesis is that ozone only affects active biomass by promoting cryptic growth. Data from a pilot-scale study were used to test this and two other model extensions to IWA-ASM3. All model extensions were able to simulate the observed linear reduction in sludge production with increasing ozone dose when the MLVSS are kept constant. However, model simulations showed the inconsistency of the cryptic growth hypothesis with the extent of sludge reduction. The second tested model extensions assumes that ozone affects all the solids fractions (active biomass, endogenous residue, and influent inert particulate COD) equally. This extension could properly simulate the observed sludge reduction, but it failed to predict the trends in effluent BOD₅, ATP/VSS, and nitrification rates. A third tested model extension, which performed better, assumes that biomass is inactivated at a specific rate higher than the specific rate of transformation by ozone of the other solids fractions. Finally, the predictions from this model extension were most accurate if either (i) the nitrifiers were inactivated at a lower rate then heterotrophs, (ii) the nitrifiers model parameters (e.g., maximum growth rate) were changed under ozone (i.e., metabolic adaptation, (iii) or both.

Improvement of Wastewater Treatment Efficiency and Deodorization by Side-Stream Humus Soil Activated Sludge Process

In wastewater treatment system, the humus soil activated sludge process is to culture microorganisms by setting the natural humus soil composite mineral filter to simulate natural soil growing conditions. After enriched and activated in the cultivation tank, the microorganisms with specific functions return to different position of activated sludge process and achieve enhanced operational performance. The project results showed the process could enhance the removal of nitrogen and phosphorus, reduce sludge production, improve sludge dewatering property and achieve odor elimination.

Hydrocycloning Influent, Mixed Liquor or Return Activated Sludge for Best Grit Removal and Sludge Production Reduction

Hydrocycloning Influent, Mixed Liquor or Return Activated Sludge for Best Grit Removal and Sludge Production Reduction