Treatment of Malting Wastewater in a Granular Sludge Sequencing Batch Reactor (SBR)

Aerobic granular sludge was successfully cultivated in a sequencing batch reactor (SBR) treating wastewater from the malting process with a high content of particulate organic matter. At an organic loading rate of 3.2 kg/(m³ d) COD_total and an influent particle concentration of 0.95 g/L MLSS an average removal of 50% in COD_total and 80% in COD_dissolved could be achieved. A comparison of granular and flocculent sludge grown under the same operating conditions showed no significant difference in removal efficiency although granules exhibited a higher metabolic activity in terms of specific oxygen uptake rate (r_{O2, X}). Two distinct mechanisms of particle removal were observed for granular sludge: during initial granule formation, particles were incorporated into the biofilm matrix. For mature granules, a high level of protozoa growth on the granule surface accounted for the ability to remove particulate COD. Combined evaluation of the development in MLSS content and sludge bed settling rate (i.e., mean derivative of the normalized sludge volume) was found to be an adequate method for monitoring the characteristic settling properties of a granulizing sludge bed. By means of this method, a distinct substrate gradient out of several operating conditions was concluded to have the biggest impact on the formation of aerobic granular sludge.     

Biokinetics of Nitrification in the Activated Sludge Process with Bioaugmentation

A laboratory study was conducted to determine the effect of bioaugmentation on nitrification performance in activated sludge process for treating municipal wastewaters. Two continuous flow bench-scale activated sludge systems consisting of 3 reactors each were operated for 30 months. The bacterial culture product used in bioaugmentation contained supplementary heterotrophic and nitrifying microorganisms. Parameters investigated included wastewater strength, hydraulic detention time, and sludge age in an activated sludge reactor system, which were low, medium and high strength; 6, 12, and 24 hours detention time; and 5, 10, and 20 days sludge age. A first reaction order mathematical model was developed for the nitrification process. Statistical fitting of the experimental data to the mathematical model allowed for determination of nitrification rate constant, decay coefficients, minimum aeration time required for initiation of the nitrification process, and the ability of the system to perform nitrification for the applied operation conditions. The results indicated that bioaugmentation improved nitrification at higher influent strength and at longer sludge age, did initiate nitrification earlier in the reactors, and did not affect the nitrification rate nor the decay coefficients.     

Modelling of nitrate leaching from arable land into unsaturated soil and chalk 1. Development of a management model for applications of sewage sludge and fertilizer

A mathematical model has been produced to examine the impact of sewage sludge and fertilizer application to arable land and the effect of different crop regimes on the amount of nitrate leached to chalk groundwater. Previous work on nitrate leaching has concentrated on either a soil science or a hydrogeological approach with little overlap between the two. This study considered both fields to obtain an overall picture of the nitrate leaching process. IMPACT is a layered deterministic N-leaching model which predicts the nitrogen loads entering groundwater daily from arable land, and can be used as a management tool in development of sludge application and agricultural policy. The model relates nitrogen species movement resulting from the application of sewage sludge and fertilizer to differing vegetation-soil-hydrogeological conditions. Field data collected at three sites on the unconfined chalk aquifer of East Anglia, England over a two and a half year period was used to produce an initial conceptual model and to constrain the mathematical model during development. IMPACT simulates nitrogen and transport processes in the soil and unsaturated zone of the chalk. The nitrogen processes include: mineralisation of soil organic-N and sewage sludge organic-N, nitrification; crop uptake; volatilization; denitrification; and N inputs from fertilizers and precipitation. A mixing cell method is used to model solute transport in both the soil and chalk. Matrix flow and combined fissure-matrix flow are considered for the chalk. The model enables examination of the relationship between the arable/hydrogeological systems and the environmental implications of sludge application and of different arable regimes. Results are of use in developing strategies for arable farming and sludge application in areas sensitive to nitrate leaching. This Part 1 paper describes the model development approach. Results of associated modelling scenarios are presented separately in the associated Part 2 paper.     

Bestimmung der Aktivität von Belebtschlamm über die Geschwindigkeit der Biosynthese von Aminopeptidasen

The authors describe a possibility of a fast determination of the metabolic activity of various activated sludge samples. There is not used the sludge property of digestion, but the biosynthesis of aminopeptidases. Egg albumin has been found to be the optimum standard indicator. The activity of the investigated activated sludge is derived from the rate of the biosynthesis of aminopeptidases. The technique proposed can be used also for determining the toxic effects of different substances on activated sludge.     

Fate of Lignin in the Process of Aerobic Biological Treatment of Paper Mill Wastewater

Although lignin is known to be not readily biodegradable the concentration of dissolved lignin decreased during aerobic biological treatment of paper mill wastewater performed in sequencing batch reactors (SBR). Systematic lab scale batch tests were conducted to clarify whether the observed removal of lignin was the result of biodegradation or adsorption onto the activated sludge. For the batch tests, sludge samples were taken from sequencing batch reactors operated at solid retention times (SRT) of 10, 15, 20, 30, and 40 days, respectively. The amount of lignin present in the bulk liquid and in the sludge samples was quantified by an analytical procedure comprising pyrolysis, gas chromatography and mass spectrometry (py‐GC/MS analysis). It was found that lignin adsorbs onto the activated sludge by up to 30%[TH]w/w. This demonstrates the sludge excellent adsorption properties. The ultimate removal of lignin is achieved by sludge wasting. The highest overall removal rate was found when sludge was used from the SBR run at SRT of 20 days.     

Bio-augmented activated sludge treatment of potato wastewaters

A laboratory study was conducted to determine the effect of bacterial augmentation with LLMO (liquid live microorganisms) on the activated sludge treatment of potato wastewaters. Completed mixed activated sludge bench scale reactors were used in this study. Parameters varied during the continuous reactor run included hydraulic detention time, LLMO addition, and powdered activated carbon addition. The hydraulic detention time lasted 1, 2, and 3 days, while the sludge age was maintained at 10 days for both reactors. The bio-augmented reactor had a better COD removal than the non-bio-augmented reactor at a lower MLVSS level in the reactor. It is concluded that bacterial augmentation with LLMO improved slightly the COD removal efficiency in treating potato wastewaters with the activated sludge process. The bio-augmentation increased the substrate removal rate, increased the oxygen utilization, and decreased the excess sludge production.     

Beneficial use of municipal sludge in the ocean

The micronutrients in municipal sludge enhance ocean productivity in much the same way as they enhance plant productivity when applied to the land. The organic solids of municipal sludge can also directly enhance production of valuable biomass in the ocean, particularly benthic biomass. Studies of municipal sludge and wastewater discharge into marine waters throughout the world have demonstrated that, if the application rate of municipal sludge or wasterwater was optimized by utilizing larger sites, beneficial enhancement of marine production could be achieved without the adverse effects associated with excessive application rates and overfertilization. Existing evidence indicates that, although not risk- or disadvantage-free, beneficial use of municipal sludges in the ocean is a viable management option which, in some instances, is likely to have fewer negative environmental side effects than other feasible beneficial use options.     

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

Sludge 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.     

Effect of Saline Sludge on Anaerobic Digestion of Kitchen Waste for Methane Generation: Modeling and Fertilizer Recovery

A comparative study of methane recovery by co-digesting kitchen waste and saline sewage sludge is performed to evaluate its feasibility for waste minimization. The experiment is performed at 37 °C having a mixing speed of 100 rpm and pH of 6.49–7.5 in anaerobic mixed batch reactors. The higher salinity level of the saline sewage sludge reduces the degradation rate of kitchen waste causing an enhancement in soluble chemical oxygen demand by 133% compared with 280% when co-digesting with the non-saline sample. The inhibitory behavior is in line with the low volatile solid elimination efficiency of 31% of saline against 55% of non-saline sludge. The Gompertz modeling, based on the outcomes, fits the cumulative methane generation trends quite well, with a strong correlation coefficient (>0.994). Besides, use of the non-saline sludge results in three times more methane production than the saline sample digestion. Sludge recovery is 0.07 m³ sludge m⁻³ wastewater, and water recovery is 0.84 m³ m⁻³ wastewater. The liquid produced from the fermentation of the slurry can be used for irrigation as well as fertilization. Kitchen waste co-digestion with both sludge samples has been proven to be a practical method for exploiting the extra digestion capacity of wastewater treatment plants currently in operation, but it is more practical for non-saline sludge.     

Modelling of nitrate leaching from arable land into unsaturated soil and chalk 2. Model confirmation and application to agricultural and sewage sludge management

A layered deterministic N-leaching model, IMPACT, has been calibrated using data from two study sites on the unconfined Chalk aquilfer of East Anglia, UK. The model predicts nitrogen species movement resulting from the application of sewage sludges and fertilizers to arable land for different vegetation-soil-hydrogeological conditions. One site received sludge in the form of digested sewage cake (DSC) for the first time during the study period, whilst the other site had over 15 years history of liquid undigested sludge (LUS) applications at 3 year intervals. Site data included: 3-monthly concentration profiles at 0.3 m intervals to depths of up to 6 m for N-species and chloride; unsaturated potential measurements; water level and saturated groundwater solute concentrations, fertilizer and sludge input; daily recharge, and soil/chalk type and moisture content. The observed average movement rate for nitrate peaks in the Lower Chalk, measured at one site, was 0.2 m year⁻². Leachate peaks were not observed annually but approximately every third year, being associated with large sludge applications and ploughing of grass crops. Significant correlation between observed and modelled nitrate profiles in soil and chalk were obtained which demonstrated applications. The relationship between crop demand, application times of fertilizers and sludge, nitrate availability and recharge was shown strongly to control the shape of nitrate profiles in the soil and chalk and the quantity of nitrate leached tochalk. The change in hydrogeological conditions at the soil-chalk contact and associated potential for denitrification was also shown to exert a significant control on the shape of the nitrate profile. Following calibration, different arable crop and sludge application regimes were examined for a 6 year period and ranked according to their nitrate leaching risk. Of the modelled cereal farming scenarios, the crop/sludge regime giving the least nitrate leaching was a late autumn surface spread application of DSC followed by winter cereals, while highest nitrate leaching was generated by an autumn injection of LUS followed by spring cereals. Field and modelled results may be used in the development of sludge disposal policies to arable land particularly with regard to sludge types, application times, and following crop types and fertilizer requirements. Overall, observed and model data demonstrate the importance of examining nitrate leaching as a continuum from the soil through the chalk to the water table.     

Removal of Hydrogen Sulfide by Physico‐Biological Filter Using Mixed Rice Husk Silica and Dried Activated Sludge

This study investigated the effectiveness of a new packing material, namely mixed rice husk silica with dried activated sludge for removing H₂S. Dried sewage sludge was collected from Putrajaya sewage treatment plant in Malaysia. Rice husk silica was prepared at temperature of 800°C, after acid leaching and mixed with dried sewage sludge to be utilized in a polyvinyl chloride filter. The system was operated under variable conditions of two parameters, different inlet gas concentration and different inlet flow rate. H₂S was passed through the filter with one liter of the packing material. More than 99.96% removal efficiency (RE) with empty bed residence time (EBRT) of 90–45 s and 300 ppm inlet concentration was observed. However, the RE decreased to 96.87% with the EBRT of 30 s. The maximum elimination capacity (EC) of 52.32 g/m³/h was obtained with the RE of 96.87% and H₂S mass loading rate of 54 g/m³/h, while at the RE of 99.96%, maximum EC was 26.99 g/m³/h with the H₂S mass‐loading rate of 27 g/m³/h. A strong significant correlation between increasing of H₂S mass loading rate and pressure drop was also detected (p < 0.01). Maximum pressure drop was 3.0 mm H₂O after 53 days of operating time, the EBRT of 30 s, and 54 g/m³/h of H₂S loading rate. These observations suggest that the mixture of rice husk silica with dried activated sludge is a suitable physico‐biological filter for H₂S removal.     

Uncertainties in mean discharges from two large South American rivers due to rating curve variability

Abstract

The aim of this study was to assess the effect of land application of sewage sludge on phosphorus (P) losses during intense rainfall. Three rainfall simulations (40 mm h^?1 of 30 min duration) were conducted on a field amended with sewage sludge. The overland flow water (OFW) was monitored and sampled every minute. The suspended solid, the dissolved and total phosphorus (respectively SS, TP and DP) concentrations were analysed. The forms of particulate bound P (PP) were investigated. Several results stem from this experiment: (a) sludge application induced a large increase in the DP content of the OFW; the concentrations obtained (0.15–0.57 mg l^?1) were shown to result from desorption processes from the SS; and (b) in contrast, sludge application affected neither the SS content nor the TP concentration of OFW (9.5 g mg l^?1 P, consisting of PP for 95%). However, sludge preserved the structure of soil surface and led to a 45% decrease in runoff rate (150 m³ ha^?1 collected on the test surface compared to 290 m³ ha^?1 on a reference). This indirectly reduced TP losses (2.7 kg ha^?1 on the reference surface compared to 1.4 kg ha^?1 on the test surface).     

Occurrence of Phthalates in Sewage Sludge from Three Wastewater Treatment Plants in Istanbul,Turkey

Phthalates are considered priority pollutants because of their potential adverse effects on ecosystems and human health. The objectives of this study were to determine the occurrence of five phthalates (DMP, DEP, DBP, BBP, and DEHP) in sewage sludge and to determine the seasonal variability of these contaminants at three (Bahçe?ehir, Pa?aköy, and Tuzla) full‐scale municipal and domestic wastewater treatment plants (WWTP) in Istanbul, Turkey. Mass balance was also calculated for DEHP at Tuzla WWTP sludge treatment units. DMP, DEP, DBP, BBP, and DEHP concentrations in sewage sludge ranged from 1.4 to 2.7 mg/kg dry weight (dw), 1.1 to 2.8, 0.6 to 4.6, 2.8 to 6.2, 18 to 490 mg/kg dw, respectively. Phthalate concentrations from the Bahçe?ehir and Pa?aköy WWTPs met the limit (100 mg/kg dw) of Turkey national sludge regulation and the Europe Union draft of sludge directive for land application, whereas phthalate concentrations from Tuzla WWTP exceeded the maximum permissible concentration. Phthalate concentrations did not show seasonal variations for Bahçe?ehir and Pa?aköy WWTPs, which receive mainly household wastewater while some fluctuations were observed DEP, DBP, and DEHP at Tuzla WWTP which has a lot of industrial wastewater contribution. The mass balance showed that approximately 17% of DEHP in the primary and secondary sludge was removed by anaerobic digestion, while 43% returned back to the beginning of the WWTP and 40% remained in the dewatered sludge. This study suggests that phthalates in sludge from WWTPs with industrial wastewater contribution may limit the use of sludge for land application.     

Optimierung des Belebungsverfahrens durch Minimierung des Volumens von Belebungs- und Nachklärbecken

The separate examination of the processes of the settling and thickening of activated sludge allows us to minimize the volumes of aeration tanks and final clarification tanks. The following initial quantities are given: wastewater quantity, inflow and outflow concentrations of BOD₅, wastewater temperature and reflux ratio of activated sludge and, in addition, three parameters of the thickening behaviour of activated sludge as well as a parameter for the bioactivity of sludge, which are to be determined in an experimental plant. From this, the optimum concentration of the activated sludge in the aeration tank is calculated at which the total of volumes for aeration tank and final clarification tank becomes a minimum. The process is carried out numerically by an example.     

Study on a comprehensive evaluation method for the assessment of the operational efficiency of wastewater treatment plants

A fuzzy matter-element model, combined with the entropy weight of an index, has been used as an evaluation method to achieve a comprehensive assessment and analysis of the operational efficiency of wastewater treatment plants (WWTPs). The feasibility of the method had been validated based on actual operational data and instance from eight WWTPs located in a city in Northern China. According to the results of the comprehensive evaluation, the operational efficiency of the WWTP using an anaerobic/anoxic/oxic process was generally better than other wastewater treating technologies. And especially, the removal efficiencies of nitrogen and phosphorus pollutants were much higher for the process, which suits well the actual operational situation of Chinese WWTPs. Total nitrogen (TN) removal rate and the productive quantity of the excess sludge cake were identified as important factors in the evaluation of the operational efficiency for a WWTP. So the operation level of WWTP could be improved by increasing the TN removal rate and decreasing the excess sludge cake quantity. The developed method can evaluate and analyze the operational efficiency scientifically and objectively, and the evaluation results can be used to guide the construction, operation and management of WWTPs in The Three Gorge reservoir district of China.     

The role and significance of extracellular polymers in activated sludge. Part I: Literature review

In biological wastewater treatment, bacteria tend to aggregate by forming flocs, biofilms and even granules. A large part of the floc structure in activated sludge is composed of extracellular polymers. The extracellular polymeric substances (EPS) are mainly responsible for the structural and functional integrity of biofilms/flocs and they are considered to be important for the physico‐chemical properties of activated sludge. This review considers the composition of EPS and proportion between the constituents. Moreover it includes the relationship between the EPS constituents and sludge properties such as sludge retention time, hydrophobicity and surface charge.     

Recovery of Phosphate Sludge as Concrete Supplementary Material

The automotive industry plays a major role in the worldwide economy and represents an opportunity to increase the performance of the Turkish economy. Phosphating units in the automotive manufacturing plants generate phosphate sludge as waste, which is classified as hazardous waste in the European Waste Catalogue. Phosphate sludge must be disposed of in licensed disposal plants according to the current environmental regulations. Solidification/stabilization (S/S) is a widely used treatment technology for the disposal of hazardous wastes. Portland cement is used for the solidification and stabilization processes to immobilize Ni and Zn in the phosphate sludge as well as to create construction material to be used as cobble stone for pavement. Examination of products obtained by S/S processes is performed for two points: to determine the quality and to assess the environmental impacts. The phosphate sludge samples are subjected to chemical characterization and a size distribution analysis leaching test. Concrete for cobble stone was produced by the S/S process with the addition of phosphate sludge to replace sand. Tests for the quality of the product were carried out to determine compressive strength, permeability, and elasticity. At the end of the leaching test, elution concentrations of Zn and Ni while using water with pH values of 4.0, 5.4, and 9.0 were determined to be under the limit of inert material properties. Use of phosphate sludge should be considered as a sand replacement in the proportion of 1% of phosphate sludge to cement in concrete production, such as for cobble stone for pavement, without any adverse environmental impacts.     

Kurzzeitermittlung der Ablaufqualität von Belebtschlammanlagen anhand der Atmungsaktivität

For checking the quality of the effluent from an activated sludge plant for waste-waters from the sulphite pulp production the respiration of an activated sludge sample in air-saturated water is determined initially without the addition of substrate (ground respiration) and after that with an addition of substrate (methanol, substrate respiration) by means of the Clark-electrode. The measuring device is designed by means of zero displacement in such a way that the difference of the oxygen concentration is indicated by a time relay as the difference quotient. Between the ground respiration and the effluent concentration of BOD₅ exists a significant positive regression, which can be used for controlling the plant. The determination of the substrate respiration serves only for checking with respect to perhaps given inhibition of the conversion of matter by the activated sludge. The determination of the activity of the activated sludge sample takes only 20 min; inclusive of the required determination of the dry matter of sludge, the technique provides a well reproducible measured value for the biochemical conversion in the activated sludge plant within 1… 1.5 h.     

Estimating particulate dispersiveness and accumulation at nearshore ocean dumpsites

The characteristics controlling the dispersion and accumulation of ocean-dumped sewage sludge are analysed for eight sites in the United Kingdom, Europe, and the United States. Based on the assumption that the sludge consists of a rain of fine materials descending on a sandy substrate, annual dispersiveness from both the local dumpsite and the dumpsite region is calculated as a fraction of sludge solids dumped during a given year. Using actual dumping amounts, indices of local and regional sludge accumulation are then calculated. The local index ranges from less than 1 for slightly impacted sites to 35 for the most severely impacted location. The regional index is less than 1 in all but one case. The index appears to be useful as a predictive tool for assessing impact from a given dumping scenario.     

Das Entwässerungsverhalten von Klärschlamm in Gegenwart von Polyelektrolyten

Dewatering Behaviour of Sludge in the Presence of Polyelectrolytes Interactions of sludge particles with well defined synthetic polyelectrolytes of different charge, molecular mass, and molecular geometry were investigated by means of zeta- and streaming potential measurements and polyelectrolyte titrations. Different mechanisms of flocculation were discussed with regard to the dewatering behaviour of the sludge. In dependence on the flocculation procedure (cationic monoflocculation, anionic-cationic, and cationicanionic dual flocculation) as well as on the chain length and branching of the polyelectrolytes used, different mechanisms of sludge dewatering were discussed: Polyanions are not adsorbed on the sludge particles and lead to a decline of the dewatering results. Linear short chain polycations result in a flocculation after surface charge neutralization of the particles according to a patch mechanism. Long chain linear polycations cause a bridging of the particles leading to a flocculation without charge neutralization of the aggregates formed. With branched polycations, a flocculation according to a patch mechanism is observed. These polycations form sludge particle aggregates which are surface charge neutralized at the flocculation point. In anionic-cationic dual flocculations using long chain polycations, an inclusion flocculation due to polyanion-polycation complex formation is the predominating mechanism. The cationic-anionic dual flocculation with complete covering of the particles with polycations in the first step can be discussed by a patch mechanism quite similar to an anionic monoflocculation of cationic particles. By knowing the mechanism of interaction for a given flocculation agent, an optimal sludge dewatering procedure can be predicted.