Dairy Sewage Sludge Research Articles

Effect of Low-Temperature Conditioning of Excess Dairy Sewage Sludge with the Use of Solidified Carbon Dioxide on the Efficiency of Methane Fermentation

This study aimed to determine the effect of the low-temperature conditioning of excess dairy sewage sludge using solidified carbon dioxide on the efficiency of methane fermentation. An increase in the solidified carbon dioxide to excess dairy sewage sludge volumetric ratio above 0.3 had no significant effect on chemical oxygen demand concentration in the dissolved phase. The highest chemical oxygen demand values, ranging from 490.6 ± 12.9 to 510.5 ± 28.5 mg·dm−3, were determined at solidified carbon dioxide to excess dairy sewage sludge ratio ranging from 0.3 to 0.5. The low-temperature conditioning caused ammonia nitrogen concentration to increase from 155.2 ± 10.2 to 185.9 ± 11.1 mg·dm−3 and orthophosphates concentration to increase from 198.5 ± 23.1 to 300.6 ± 35.9 mg·dm−3 in the dissolved phase. The highest unitary amount of biogas, reaching 630.2 ± 45.5 cm3·g o.d.m.−1, was produced in the variant with the solidified carbon dioxide to excess dairy sewage sludge volumetric ratio of 0.3. Methane content of the biogas produced was at 68.7 ± 1.5%. Increased solidified carbon dioxide dose did not lead to any significant changes in biogas and methane production. The efficiency of biogas production from unconditioned excess dairy sewage sludge was lower by 43.0 ± 3.2%. The analysis demonstrated that the low-temperature conditioning is an energetic viable technology aiding the methane fermentation process.

Community shift in structure and functions across soil profile in response to organic waste and mineral fertilization strategies

Significant differences in the microbial diversity, biochemical processes and enzyme activity in soil has been observed under various conditions of fertilization, but to date little research has been performed to explore these properties across soil profile after organic waste amendments, especially within deeper soil layers. Soil samples were collected from an experiment under winter wheat, and enzyme activity, microbial community structure were determined. All treatments amended with organic waste or mineral fertilizers and non-amended plots had different microbial communities, especially in various soil layers. Greater enzyme activity (9.82 mg PNP kg−1 h−1, 13.41 mg TPF kg−1 d−1), ammonification (44.31 mg NH4+ kg−1 d−1), and CO2 production (375.16 mg CO2 kg−1 d−1) were observed in the rhizosphere soil amended with dairy sewage sludge. Conversely, lower enzyme activity, ammonification, and CO2 production were detected in the deep soil layer (30–40 cm) compared to rhizosphere and non-rhizosphere soil. Overall, it was demonstrated that organic waste amendment supports soil microbial diversity and leads to enhanced functional potentials expressed as enzyme activity.

Research of Effective Microorganisms on Dairy Sewage Sludge Stabilization

Research of Effective Microorganisms on Dairy Sewage Sludge Stabilization

Characterization of microbial functional and genetic diversity as a novel strategy of biowaste ecotoxicological evaluation

The goal was to elucidate the importance of the waste properties for effective exploitation in biogas production and for soil application, respectively, based on the physicochemical and microbial characterization of biowaste and the corresponding biogas residues. The following waste media were chosen: fruit waste, dairy sewage sludge, corn silage, grass silage, and grain brew to prepare three co-substrates for anaerobic bioconversion. The most satisfactory biogas yield was obtained from biowaste with the following composition: 25% fruit wastes, 25% dairy sewage sludge, 12% corn silage, and 38% grain brew. The study included functional and genetic diversity assessment through the characterization of the catabolic potential and structure of the microbial communities inhabiting the examined organic wastes and their relative biogas residues. The metabolome was based on the use of a Biolog® plate. The elucidation of the metagenome employed the genetic structure of prokaryotes and involved denaturing gradient gel electrophoresis and next-generation sequencing analyses. The usefulness of metagenomics was emphasized by ecotoxicological evaluation of biowaste and in determining the accurate start-up community composition for biogas production, highlighting the pivotal role of anammox and hydrolytic bacteria as marker groups. The high importance of the great diversity of fungi was also revealed based on a functional approach.

Evaluation of microbial community composition of dairy sewage sludge, corn silage, grass straw, and fruit waste biomass for potential use in biogas production or soil enrichment

The purpose of the study was to link microbial community composition and chemical properties of various biomass and their resulting digestate residues for their potential use in biogas production or soil enrichment. The order of biogas production, graded from high to low was as follows: corn silage, grass silage, fruit waste, and dairy sewage sludge. Different bacterial families were predominant in different biomass. Corn silage deteriorated as a result of long-term air exposition and may serve as an efficient feedstock substrate for anaerobic digestion. A positive role in plant biocontrol microorganisms found in grass straw residues, and reasonable biogas yield obtained from this substrate suggests the use of grass straw for biogas production and its residues to enrich the soil. Due to potential threat of introducing pathogens into the soil within fruit waste or dairy sewage sludge, or soil acidification by fruit waste repeated use in field application, this biomass should be sanitized prior to soil application. Simultaneously, low biogas yields from fruit waste and dairy sewage sludge substrates make it necessary to transform them in anaerobic digestion with more energetic co-substrates. Tested residues may deliver a robust and wide range of methanogens as inoculum for further anaerobic digestion process.

Characterization and Influence of a Multi-enzymatic Biopreparation for Biogas Yield Enhancement

A multi-enzymatic biopreparation of Trichoderma atroviride G79/11 origin was characterized. The fungus showed relatively high cellulase production in a soybean flour-cellulose-lactose medium. Subsequently, based on its post-culture liquid, the biopreparation of the enzyme mixture was developed and characterized. The liquid form of the enzyme mixture reached 22 U cm-3 of cellulolytic activity and its lyophilisate exhibited 1.09 U cm-3 at pH 5.1 and 50 °C. The enzyme mixture was characterized by the following activities: xylanase, β-glucosidase, carboxymethyl cellulase, polygalactouronase, pectinesterase, amylase, lactase, and protease. A method for an efficient conditioning process of organic waste (fruit processing waste, dairy sewage sludge, corn silage, and grain broth) for biogas yield enhancement using the enzyme mixture was proposed. The enzyme mixture increased the efficacy of biogas production by 30% when the lyophilizate (0.5 mg g-1 d.m.) was applied prior to fermentation. A method for conducting the enzymatic conditioning process of organic waste using the enzyme mixture as a pretreatment was proposed. This was part of the optimization of the methane fermentation process to increase the biogas yield. Consequently, after application of the biopreparation, the efficiency of anaerobic digestion of organic waste was improved.

Research on the influence of anaerobic stabilization of various dairy sewage sludge on biodegradation of polycyclic aromatic hydrocarbons PAHs with the use of effective microorganisms

Sewage sludge was taken from a dairy WWTP belonging to Mlekovita Cooperative in Wysokie Mazowieckie. There were excess sludge, flotation sludge and a mixture of excess and flotation sludge from pre-treatment of dairy sewage.The initial content of 16 PAHs in excess sludge before fermentation was approximately 689µg·kg−1 in dry mass, whereas in post-flotation sludge (which constituted around 30% of raw sludge) it was approximately 95µg·kg−1 in dry mass. A mixture of excess and flotation sludge had the content of 497,7µg·kg−1 in dry mass. Through comparison of particular hydrocarbons content in raw sewage sludge to the total PAHs content, it was shown that tricyclic compounds, which constituted 46,3% of the PAHs sum (excess sludge), and tetracyclic compounds, which constituted 60,0% of the PAHs sum (flotation sludge), were the dominating fractions.In the sludge subjected to fermentation in reactors with mixed sludge and surplus activated sludge, the general trend of the course of changes in concentrations of PAHs was similar. Both in the sludge inoculated with EM and in that not inoculated with EM, a significant increase in the total PAHs contents was observed in the first fermentation phase (acidic fermentation) after 7 days of the process. Addition of EM into the sludge did not prevent the PAHs release, and therefore higher concentrations of PAHs sum were recorded during the hydrolysis stage than in sludge before fermentation. A decrease in the sum of PAHs was observed after 2 weeks of fermentation in relation to the quantity observed after 1 week of fermentation (except from post-flotation sludge). In the following weeks, there was further decrease in the concentration of the 16 PAHs sum in all sludge types. However, in sludge without EM inoculation, it was lower than in sludge with EM inoculation. The loss of the majority of tested hydrocarbons was reported in the final phase of fermentation.

Assessment of microbiological and biochemical properties of dairy sewage sludge

The rational utilisation of sludge as organic matter application into the soil permits enrichment in nutrients such as nitrogen and phosphorus. As dairy sewage sludge contains large amounts of organic matter and minerals, utilisation of such sludge in agriculture appears to be a noteworthy proposal. However, such waste can also be a source of toxic substances, heavy metals, inhibitors, xenobiotics and potentially pathogenic microorganisms. Therefore, it is so important to monitor its microbiological and biochemical properties in aspect of the safety for human health, natural environment preservation and a suitable level of agricultural production maintenance. The objective of study was the estimation of selected microbiological, biochemical and chemical properties of activated sludge (AS) and waste activated sludge (WAS) originating from the dairy sewage treatment plant. Nitrification and ammonification rates, respiratory, dehydrogenases, acid phosphatase, alkaline phosphatase, protease and urease activities were at significantly higher levels in the WAS than in the AS. The pH value of the AS and WAS oscillated within the range of neutral reaction.

Soil microbial functionality in response to dairy sewage sludge and mineral fertilisers application under winter rape

Microbial activity and the diversity of their catabolic potential would be stratified according to soil profile as a result of differing content of soil organic C and they would be altered by applying dairy sewage sludge (DSS) to the surface and subsequently ploughing. We applied 26 Mg ha−1 of DSS and the same nutrient dose of mineral fertilisers as an NPK reference to the soil before sowing winter rape (Brassica napus) in the field experiment. We evaluated the impact of the fertilisers on microbial activity, measured with dehydrogenase and respiratory activity, and diversity of the microbes’ catabolic potential from non-rhizosphere and rhizosphere soil at selected depths. In the surface rhizosphere soil, there were significant increases in microbial catabolic potential (>25 %) and respiratory activity (>20 %) due to DSS application. All of the microbial parameter values in non-rhizosphere soil were higher at 0–20 than at 25–30 cm. These results are important for improving the management approach of diary sewage sludge application to agricultural soils in the context of increasing microbial activity in the soil profile and reducing mineral fertiliser use.

The effect of dairy sewage sludge amendment on repellency and hydraulic conductivity of soil aggregates from two depths of Eutric Cambisol

AbstractAppropriate management of sewage sludge is an important worldwide issue due to the still growing amount of wastewaters. In the study we examined to what extent the addition of dairy sewage sludge compared with mineral fertilization affects porosity, repellency index, and hydraulic conductivity of variously sized aggregates from two soil depths of Eutric Cambisol derived from loess: 5–15 cm and 25–35 cm. The repellency index was calculated as a ratio of ethanol and water sorptivity. Data on water and ethanol sorptivities of initially air‐dry soil aggregate fractions were obtained from steady state flow measurements using an infiltration device. Hydraulic conductivity was determined by measuring water infiltration at five pressure heads: –8, –6, –4, –2, and 0 cm of water column with the same device as for sorptivity determination. Addition of sewage sludge to the soil decreased the soil repellency index by an average of 27% in topsoil and 32% in subsoil for both aggregate sizes, respectively, and increased hydraulic conductivity about four times in both layers. Smaller aggregates (15–20 mm diameter) from soil amended with sewage sludge, in comparison with larger ones (30–35 mm diameter), had a higher repellency index by 36 and 24% in topsoil and subsoil, respectively. As for aggregates from soil with mineral fertilization, those differences were smaller and equal to 15% in subsoil, in topsoil smaller aggregates even had slightly lower repellency index (by 5%). Aggregates taken from the upper soil layer were more water repellent and had smaller hydraulic conductivity than those taken from subsoil, regardless of soil treatment and aggregate size.

The Application of the Biolog EcoPlate Approach in Ecotoxicological Evaluation of Dairy Sewage Sludge

An increasing amount of sewage sludge requires reasonable management, whereas its storage might be environmentally hazardous. Due to the organic matter and nutrient presence in sediments, it may be used as organic fertilizer. However, beyond the valuable contests, sewage sludge can also contain toxic or dangerous ingredients like heavy metals. Therefore, there is a need to develop methods for rapid assessment of sediment ecotoxicity that will determine its possible applicability in agriculture. The Biolog® EcoPlate enables the metabolic profile diversity evaluation of microbial populations in environmental samples, which reflects the state of their activity. It is regarded as a modern technology that by means of biological properties allows quick characterization of the ecological status of environmental samples, such as sewage sludge.

Community Level Physiological Profiles (CLPP), Characterization and Microbial Activity of Soil Amended with Dairy Sewage Sludge

The aim of the present work was to assess the influence of organic amendment applications compared to mineral fertilization on soil microbial activity and functional diversity. The field experiment was set up on a soil classified as an Eutric Cambisol developed from loess (South-East Poland). Two doses of both dairy sewage sludge (20 Mg·ha−1 and 26 Mg·ha−1) and of mineral fertilizers containing the same amount of nutrients were applied. The same soil without any amendment was used as a control. The soil under undisturbed native vegetation was also included in the study as a representative background sample. The functional diversity (catabolic potential) was assessed using such indices as Average Well Color Development (AWCD), Richness (R) and Shannon–Weaver index (H). These indices were calculated, following the community level physiological profiling (CLPP) using Biolog Eco Plates. Soil dehydrogenase and respiratory activity were also evaluated. The indices were sensitive enough to reveal changes in community level physiological profiles due to treatment effects. It was shown that dairy sewage amended soil was characterized by greater AWCD, R, H and dehydrogenase and respiratory activity as compared to control or mineral fertilized soil. Analysis of variance (ANOVA) and principal component analysis (PCA) were used to depict the differences of the soil bacterial functional diversity between the treatments.

Agricultural utilisation of dairy sewage sludge: Its effect on enzymatic activity and microorganisms of the soil environment

Biochemical indices related with the transformations of C, N and P are frequently used in the diagnosis of soil quality. Such an assessment usually includes analysis of the following enzymes – the activity of dehydrogenases and of hydrolytic enzymes such as phosphatases, urease and protease. The objective of the study presented here was evaluation of dairy sewage sludge as an agent causing an improvement of soil quality or its degradation. Estimation of soil quality was performed on the basis of a comprehensive study comprising analyses of microbiological and biochemical parameters. The results of the study indicate a stimulating effect of dairy sewage sludge on the soil microorganisms, which was apparent also as an increase in the activity of the enzymes studied. That effect should be attributed to soil enrichment in organic matter, total nitrogen and minerals. Key words: Dairy sewage sludge, enzymatic activity, microorganisms, soil.

Effects of microwave pretreatments on the anaerobic digestion of food industrial sewage sludge

AbstractMicrowave irradiation is a novel and very promising technology for sludge conditioning. As pretreatment, it has a verified beneficial effect on the microbial degradation and anaerobic digestion of sewage sludge, but in present work we dealt with the applicability of microwave pretreatments for food industrial sludge. However, studies cannot be found that specialize on the effects of the MW treatments with different intensities on the anaerobic digestion of sludge. In our work we focused on the examination of the effect of MW pretreatment for 0.5, 2.5, and 5 W/g on the carbonaceous biochemical oxygen demand (CBOD5), solubilization of organic matters (sCOD/tCOD), and the mesophilic anaerobic digestion of dairy sewage sludge. It can be concluded that the MW pretreatments were appropriate to enhance the efficiency of anaerobic digestion. With MW pretreatments the specific biogas product could be increased from 220 mL g−1 to more than 600 mL g−1 because of the increased solubility (from 9.7% to more than 40%), and the enhanced accessibility of organic compounds for decomposing bacteria. © 2010 American Institute of Chemical Engineers Environ Prog, 2011

Microbiological Hazards Resulting from Application of Dairy Sewage Sludge: Effects on Occurrence of Pathogenic Microorganisms in Soil

The aims of this study were to (1) examine the extent of bacterial contamination of soils subjected to exposure to dairy sewage sludge applied to soils as measured by determination of number of bacteria from the Escherichia coli family and (2) determine the effects of dairy sewage sludge and straw on populations of other microbial species present in gray–brown podzolic soil. The gray–brown podzolic soil was formed from heavy loamy sand, which is characterized by the following granulometric composition: a sand fraction, 65%; a silt fraction, 19%; and a silt and clay fraction; 16%. The brown soil was formed from silt-loam and characterized by the following granulometric composition of silty–clay deposit: sand fraction, 8%; silt fraction, 48%; and clay and silt fraction, 46%. In dairy sewage sludge the total bacteria number as defined by Alef and Nannipieri (1995) was 51 × 104 colony-forming units (cfu)/ kg dry matter (dm), fungi total number 10 × 103 cfu/ kg dm, and E. coli bacteria 9.5 × 103 most probable number (MPN)/kg dm. In dairy sewage sludge mixed with straw, total number of bacteria and total number of fungi decreased to 103 and 102, respectively. Competition for nitrogen, glucose, and lactose and organic acids such as acetic and succinic with soil microorganisms, as well as soil conditions such as lack of oxygen, lower soil pH, and temperature, may account for the reduction in the number of E. coli bacteria in soils to which dairy sewage sludge was applied. Dairy sewage sludge may provide a beneficial impact on soil environment and adversely affect microorganisms such that dairy sewage sludge may be used as a safe organic fertilizer.

Changes of microbial activity of brown soil under winter wheat cultivation in different years of the influence of dairy sewage sludge

Changes of microbial activity of brown soil under winter wheat cultivation in different years of the influence of dairy sewage sludge