Dairy Sludge Research Articles

A novel psychrotrophic, solvent tolerant Pseudomonas putida SKG-1 and solvent stability of its psychro-thermoalkalistable protease

It is the first time when psychrotrophic, solvent tolerant, psychro-thermoalkaline protease producing strain of Pseudomonas putida isolated from dairy sludge was capable of growing in the presence of 30% (v/v) organic solvents. The strain exhibited resistance against heavy metals (Cr 6+, As 3+, Pb 2+, Cs 1+) and various antibiotics. The isolate was able to grow at wide range of temperature (10–40 °C) with maximum growth at 25 °C. In glucose gelatin yeast extract (GGY) broth (pH 9.0 and 25 °C), the strain produced 514 U Protease ml −1. The presence of organic solvents n-dodecane, n-decane, isooctane and n-octane, enhanced the protease production. The protease was not only stable but also its activity enhanced in the presence of 25% (v/v) solvents n-dodecane, n-decane, isooctane, n-octane, n-hexane, n-butanol, n-heptane, cyclohexane and xylene, after prolonged incubation of fourteen days. The molecular weight of purified protease was ∼53 kDa as revealed by SDS-PAGE and activity gel analysis. The protease was active in broad pH and temperature range of 8.0–12.0 and 10–70 °C, respectively, with maxima at pH 9.5 and 40 °C. The unique property of solvent tolerance, antibiotic and heavy metal resistance proves the potential candidature of this isolate not only for peptide synthesis, but also for industrial use and bioremediation strategies involved in environmental clean up.

GIS-based dairy-industry sludge application plan in Galiza (NW Spain)

A site-specific dairy-industry sludge application plan (GIS-based) has been development in Vilalba municipality, Galiza (NW Spain). Sites suitable for sludge application were identified using GIS based weighted linear combination (WLC) model. The degree of land suitability for dairy sludge was determined using a range of environmental, agronomic and socio-economic factors: water runoff and groundwater risk of pollution, heavy metals input to system, proximity to watercourses and potable water sources, presence of sensitive areas (protected and flooded land), land use, soil depth, plot suitability for mechanisation, distance from human settlements and main roads, and sludge spread cost were included in the model.

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.

Removal of heavy metal ions from aqueous solutions by a local dairy sludge as a biosorbant

In this work, the removal of lead and cadmium from an aqueous solution by a local dairy sludge was investigated in a batch system. Biosorption of these heavy metals was studied as a function of solution initial pH, equilibrium time, temperature, biosorbent dose, biosorbent particle diameter and initial metal ion concentration. Maximum sorption was observed at a pH value of 5 and a temperature of 40 °C. Equilibrium uptake increased with increasing metal ion concentration for both metals with a maximum sorption capacity of a 148.6 mg/g for Pb (II) and 66.7 mg/g for Cd(II). The Langmuir model was found to better describe the sorption of lead ions with a correlation factor of 0.99 while Freundlich and Temkin models were better for Cd(II) sorption. The temperature increase from 20 to 40 °C enhanced the uptake of Pb(II) by 20% and Cd(II) by 5%. The sorption kinetics were compatible with the pseudo-second order model for the systems investigated. SEM micrographs were determined before and after sorption. Nitric and hydrochloric acids were used for the metals desorption. Pb(II) was better desorbed by nitric acid whereas Cd(II) was eluted slightly better by chlorhydric acid.

Management of waste organic matters and residential used water for culture and biomass production of red worm (Tubifex tubifex) ***DON'T INCLUDE - DUPLICATE OF PREVIOUS RECORD ***

The efficacy of red worm (Tubifex tubifex) for converting organic wastes like pig dung, poultry excreta and dairy sludge into worm biomass production was investigated. For this purpose, three experiments each for pig dung, poultry excreta and dairy sludge were conducted in cement trenches for 90 days duration. The poultry excreta produced maximum biomass (126.53 ± 2.16 g), followed by the pig dung (99.47 ± 2.07 g) and dairy sludge (10.09 ± 2.55 g). Waste water discharged from residential area was used for circulation in experimental trenches.

Bioaccumulation and phyto-translocation of arsenic, chromium and zinc by Jatropha curcas L.: Impact of dairy sludge and biofertilizer

The present study was planned to remediate the metalloid and metal contaminated soil by using non-edible and economic plant species Jatropha curcas L. The experiment was conducted on pots to improve the survival rate, metal tolerance and growth response of the plant on soil; having different concentrations of arsenic, chromium and zinc. The soil was amended with dairy sludge and bacterial inoculum ( Azotobacter chroococcum) as biofertilizer. The results of the study showed that the bioaccumulation potential was increased with increase in metalloid and metal concentration in soil system. Application of dairy sludge significantly reduces the DTPA-extractable As, Cr and Zn concentration in soil. The application of organic amendment stabilizes the As, Cr and Zn and reduced their uptake in plant tissues.

Bacterial community composition and chitinase gene diversity of vermicompost with antifungal activity

Bacterial communities and chitinase gene diversity of vermicompost (VC) were investigated to clarify the influence of earthworms on the inhibition of plant pathogenic fungi in VC. The spore germination of Fusarium moniliforme was reduced in VC aqueous extracts prepared from paper sludge and dairy sludge (fresh sludge, FS). The bacterial communities were examined by culture-dependent and -independent analyses. Unique clones selected from 16S rRNA libraries of FS and VC on the basis of restriction fragment length polymorphism (RFLP) fell into the major lineages of the domain bacteria Proteobacteria, Bacteroidetes, Verrucomicrobia, Actinobacteria and Firmicutes. Among culture isolates, Actinobacteria dominated in VC, while almost equal numbers of Actinobacteria and Proteobacteria were present in FS. Analysis of chitinolytic isolates and chitinase gene diversity revealed that chitinolytic bacterial communities were enriched in VC. Populations of bacteria that inhibited plant fungal pathogens were higher in VC than in FS and particularly chitinolytic isolates were most active against the target fungi.

Use of dairy sludge for the removal of some basic dyes

Dairy sludge, which is produced as a result of the activated sludge process, used in the dairy processing industries for treating their effluents, is a low cost, locally available and relatively new adsorbent. It is being investigated for its capacity to remove some of the basic dyes such as aniline blue, crystal violet, malachite green, methylene blue, rhodamine-B, and safranine from aqueous solutions. The effects of various experimental parameters;; initial pH, dye concentration, sorbent dosage, ion strength, and contact time, were examined and optimal experimental conditions were decided. At initial basic pH of 10, all six of the dyes studied could be removed effectively and in a very short period of time of just 35 min. The isothermal data for adsorption followed the Freundlich and Langmuir models. The adsorption results in this study indicated that all the dyes studied in this work can be easily removed by the application of dairy sludge.

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

In situ near Infrared Monitoring of Activated Dairy Sludge Wastewater Treatment Processes

A sequential batch reactor (SBR) for aerobic treatment of dairy residues (activated sludge process) was monitored on-line by near infrared (NIR) spectroscopy. NIR spectra in the wavelength range of 900–1700 nm were acquired in situ with a transflectance probe. Measured in situ NIR spectra allowed the development of multivariate statistical process control models for supervision of the SBR process. The directly acquired spectra permitted characterisation of the different SBR operation stages and the detection of process disturbances. Calibration models based on partial least squares regression were developed for three process parameters: total solids (TS), total suspended solids (TSS) and chemical oxygen demand (COD). Model errors were estimated as root mean squared errors of cross-validation. The cross-validation errors obtained were 0.066 g TS L−1, 0.075 g TSS L−1 and 86.6 mg O2 L−1 respectively. Results demonstrated the viability of NIR spectroscopy as an alternative method for monitoring and control of activated sludge wastewater treatment processes having advantages both in terms of efficient determination of process parameters (fast, in situ and requiring no toxic reagents) and in terms of process monitoring.

Manipulating Nitrogen Release from Nitrogen‐Rich Crop Residues using Organic Wastes under Field Conditions

Following mineralization of N‐rich crop residues, large amounts of mineral N can be released into the soil. Manipulating N mineralization of crop residues may be an option to reduce NO3− in soil. The potential to manipulate the N release from vegetable crop residues by using organic wastes was tested under field conditions. At the start of the experiment, cauliflower (Brassica oleracea L. var. botrytis L.) residues (∼73 Mg fresh matter ha−1) together with an immobilizer waste (∼5 Mg C ha−1 of straw, green waste compost, sawdust, or paper sludge) were incorporated into a silt loam soil. After 154 d, a remineralizing waste (∼1 Mg C ha−1 of vinasse or dairy sludge) was incorporated. During the field experiment, the mineral N content in the soil was measured at regular time intervals, and net N release, NO3− leaching, and denitrification were simulated using a N mineralization–immobilization model coupled to a NO3− leaching model. Straw, green waste compost, and sawdust were able to immobilize between 54 and 68% of the N released by the cauliflower residues and reduced NO3− leaching by 56 to 68%. Paper sludge released an extra amount of N due to its low C/N ratio. No consistent remineralization of N could be found in any of the treatments, probably due to an unsuitable composition of the remineralizer wastes. Manipulating N release of N‐rich crop residues by using organic wastes may be a suitable method to reduce NO3− leaching; however, stimulating remineralization of immobilized N by the start of the following spring may not be easy to achieve.

Effect of amendment on phytoextraction of arsenic by Vetiveria Zizanioides from soil

The present study was undertaken to evaluate the growth response of Vetiveria zizanioides amended with organic amendments to arsenic (As) in contaminated soils and its ability to sequester As. The test results indicate that the plants exhibited high tolerance to As in the soils and their normal growth continued even though As concentration reached 500 mg/kg. However, when As concentrations in soils were in the range of 1000~2000 mg/kg the plants could not survive no matter whether the soils were amended. The accumulation of As in roots (185.4 mg/kg) was higher than that in shoots (100.6 mg/kg). The As level in the contaminated soil was reduced from 500 mg/kg to 214 mg/kg after six months of As phytoextraction. Microbial population was not affected in the As contaminated soil amended with dairy sludge, mycorrhizae and Azotobacter.

Growth of Jatropha curcas on heavy metal contaminated soil amended with industrial wastes and Azotobacter – A greenhouse study

The aims of the study were to evaluate the effect of organic wastes (biosludge and dairy sludge) and biofertilizer ( Azotobacter chroococcum) on the planting conditions of Jatropha curcas in metal contaminated soils. Results showed that the plants survival rate in heavy metal contaminated soil increased with addition of amendments. Treatment T6 (heavy metal contaminated soils + dairy sludge + biofertilizer) observed to be the best treatment for growth (height and biomass) as compared with the treatment T5 (heavy metal contaminated soils + biosludge + biofertilizer). In addition, organic amendments provided nutrients such as carbon, N, P and K to support plant growth and reduced the metal toxicity to plant. The present study showed that metal contaminated lands/soils could be suitably remediated by adapting appropriate measures.

Pasture, tree and soil evolution in silvopastoral systems of Atlantic Europe

Increased forest area and wood production is a key goal for the European Union, together with avoidance of hazards that damage forests. Galicia is a region of northwest Spain that belongs to the Atlantic biogeographic region with very high wood production, but due to climate fire has a major negative impact on forest productivity (i.e. it represents 16% of the fires of Europe). Silvopastoral systems offer the potential to enhance forest productivity as well as to obtain income from newly afforested areas in the short term. Herbaceous pasture production within such systems can be optimized through species selection and through fertilization. The aim of the present study was to evaluate effect of three types of fertilization on two sward mixtures established under Pinus radiata D. Don cover on abandoned agricultural land over an initial period of 7 years. Tree and pasture growth were enhanced with organic fertilization, tree growth rate not being limited by summer drought, and compared with mineral treatment, trees growing up on sludge treatment had around 35 and 30% more height and diameter, respectively. Acidity tendency of Galician soils was reduced with mineral treatment. Soil pH was positively affected by mineral fertilization as it was reduced in less extent in this treatment (pH 6) than in organic (pH 5.3) or no fertilization treatment (pH 5.6), as crop cation extractions were reduced. The proportion of Na and Mg in the effective CEC was higher in fertilization with dairy sludge and no fertilization plots due to better tree canopy development. The interchangeable potassium content in ryegrass sown plots was reduced when no fertilization was applied due to dicot extractions, which can explain lower tree growth than in non-fertilized cocksfoot plots. Correct tree and pasture management, using appropriate sowing mixtures and fertilization types, makes it possible to improve the productivity of both components of the silvopastoral system. Our present results indicate that it is better to use organic fertilizers in the establishment of cocksfoot or ryegrass on sandy soils for tree and pasture growth enhancement.

Screening organic biological wastes for their potential to manipulate the N release from N-rich vegetable crop residues in soil

Abstract In a laboratory study, organic biological wastes (OBW) were screened for their potential to manipulate the N release from vegetable crop residues in two phases: an immobilization and remineralization phase. During the first phase, celery leaves (Apium graveolens L.) were mixed with an immobilizer waste (straw, two green waste composts (GWC1 and GWC2), saw dust, paper sludge and tannic acid) in order to immobilize N released from crop residues. During the second phase, the treatments received a remineralizer waste (malting sludge, vinasses, molasses and dairy sludge) in order to stimulate remineralization of immobilized N. Straw showed the most pronounced N immobilization (on average 30.2 mg N kg−1). N immobilization with tannic acid, saw dust and GWC2 was slower and less pronounced (on average 16.4, 15.9 and 8.0 mg N kg−1, respectively). GWC1 and paper sludge immobilized almost no N. Only when GWC1 was mixed with vinasses, remineralization was observed (up to 55.4 mg N kg−1) during a 30 days period. For all other remineralizers, positive priming effects were scarce and short-lived. Manipulating the N release of N-rich crop residues may be a suitable method to reduce the nitrate concentration in soil after incorporation of crop residues. Especially, easily decomposable waste materials (i.e. low lignin content) with a large C:N ratio seem to have a potential to immobilize N. However, stimulating remineralization of immobilized N seems not easy to accomplish.

Nitrogen leaching losses from different forms and rates of farm effluent applied to a Templeton soil in Canterbury, New Zealand

The leaching losses of nitrogen from a range of farm effluents and wastes, including pig slurry, dairy pond sludge, farm‐dairy effluent, and cow urine are compared on a Templeton fine sandy loam. At similar rates of application, leaching losses decreased in the following order: cow urine>pig slurry>farm‐dairy effluent>dairy pond sludge. The susceptibility to leaching is determined by the forms of the N in the waste, and a high N:C ratio alone is not an adequate predictor of leaching intensity. Nitrate is most susceptible to leaching, followed by ammonium and organic forms of N. Splitting the applications of effluent into two or four portions applied at different times reduced the overall quantity of nitrate leached by c. 30%, depending on the waste. Similarly, reducing the overall rate from 400 to 200 kg N/ha also reduced the N leaching loss by c. 30%, depending on the particular waste. It is recommended that the land application of farm waste be based on a knowledge of the propensity of different kinds of wastes to contaminate groundwater, especially with nitrate‐N. An effective mitigation technology to reduce nitrate leaching from grazed pasture soils is to treat the soil, including cow urine areas, with a nitrification inhibitor, e.g., dicyandiamide (DCD), which has been found to reduce nitrate leaching losses by 60%, decrease nitrous oxide emissions by over 75%, and increase pasture yield by over 10%.

A new side stream process for easily degradable industrial waste waters to avoid sludge bulking

A new treatment scheme for the treatment of easily biodegradable industrial waste waters has been developed. The side stream treatment of dairy waste water with the excess sludge from the domestic treatment line of the regional treatment plant Bad Vöslau has been operated successfully for a period of three years during which the industrial load stemming from the dairy increased from 800 kg COD/d to 2,500 kg COD/d with peak loads up to 5,000 kg/d. Despite of the increased load to the treatment plant the total aeration tank volume had not been increased. This treatment is performed in an existing aeration tank of the WWTP (V = 1,800 m3) which is now used as contact tank for the combined aeration of dairy waste water and excess sludge from the domestic treatment line (volume aeration tank = 15,000 m3). In this tank the easily degradable substrate from the industrial waste is mainly adsorbed to the biological sludge and after a mechanical dewatering transferred to the anaerobic digester where it yields in an increased gas production. The filtrate of the dewatering process is completely free from biodegradable material and can without danger of bulking be fed to the aeration tank of the domestic treatment line. The new process has proven to be extremely flexible since already now daily peak loads exceeding the design load by more then 60% could be treated in the plant without any problems. Compared to other alternatives for the dairy waste water treatment that were investigated during this study, the new side stream process is very advantageous. No other pre-treatment process for industrial waste water could have been operated under comparable loading conditions without severe operating problems.

Comment on “Sorption of basic dyes from aqueous solution by activated sludge” [J. Hazard. Mater. 108 (2004) 183–188

Effluents discharged from electronics manufacturing industry, thermal power plants, electroplating industries, mining, and tanneries are the prime sources of toxic heavy metal pollutants that contaminate freshwater bodies and posing risks to living organisms and the environment. Besides these, the wastewater discharged from textile, ceramic and leather industries contains various toxic high colored organic dyes that can act as a mutagen or carcinogen even at lower concentrations affecting mankind and aquatic organisms. Therefore, it is necessary to treat these effluents coming from industries containing toxic heavy metals and carcinogenic dyes by industry or by government mechanism before discharging them into water bodies. Easy availability and the presence of several functional groups in biowastes such as cheese, whey protein make them remarkable renewable adsorbents that can be applied for adsorptive removal of heavy metals and dyes from contaminated water. Major water pollutants are heavy metals and portable water polluted with higher concentrations of heavy metals, i.e., above the permissible limit recommended by WHO could induce cancers, diabetes, hypertension, kidney disorders, lung diseases, brain damage and may even be fatal to living organisms. Secondly, dyes are the most common dangerous pollutants found in industrial effluents. These water-soluble organic dyes decompose under light or oxidant agents and curtail photosynthesis in aquatic plants. Moreover, cationic dyes are more toxic than anionic dyes because they interact with negative charges on surface of cell membrane and penetrate the cell membrane of aquatic organisms. Among numerous chemical, physical and biological processes available to treat wastewater, adsorption process is found to be a simple, economical, efficient, flexible, and preferred physicochemical treatment method to effectively treat many industrial wastewater before reaching the natural environment. Surface functionalization or coating or surface modification of biowaste adsorbent is essential to enhance its adsorption capacity. In recent years many researchers focus on using modified protein biowaste as adsorbents due to their superior biodegradability and excellent biocompatibility. Cheese whey protein is the biowastes produced as a major by-product in the dairy industry that is discharged in the dairy wastewater. With the above considerations, the present chapter aims to highlight the efficacy of renewable adsorbant for the adsorption of both cationic and anionic heavy metals and dyes on pretreated protein. This chapter also deals with characterization methods to study the morphology of the adsorbent, change in the surface charge, and functional groups involved in adsorption. The later part of the chapter reviews the successive adsorption behavior of anionic and cationic heavy metals and dyes on the biowaste adsorbents using adsorption isotherm models and kinetic analysis. The objectives of the present chapter, therefore include evaluation of the efficacy of dairy processing sludge in the removal of pollutants from wastewater, highlighting the possible mechanisms involved in adsorptive removal of pollutants, identifying the parameters that enhance the removal capacity of the adsorbents, and proposing a regeneration mechanism for reuse of the dairy processing sludge derived products. This chapter provides plausible approaches for the efficient utilization of dairy sludge for wastewater purification.

Use of dairy-industry sludge as fertiliser for grasslands in northwest Spain: heavy metal levels in the soil and plants

The suitability of dairy-plant sludge for fertilisation of a Cambisolic soil was investigated in northwest Spain. Soil properties (pH, electrical conductivity, organic matter content, NO3−, P, Ca, Mg, Na, K and Al) and soil and plant tissue heavy metal contents (Hg, Pb, Cd, Cu, Zn, Ni and Cr) were determined in 12 grassland plots fertilised over a 1–4-year period with dairy sludge and conventional fertiliser (cattle slurry and mineral fertilisers), and in six meadows fertilised with conventional fertilisers only. Heavy metal contents were also determined in plant tissues from different plots. There were no significant differences in soil heavy metal concentrations between the sludge-amended plots and the control plots, except for Pb concentration, which was significantly lower in the sludge-amended plots. A significant correlation between metal content in the soil and total sludge dose applied was detected only for Cr. Even in plots to which the dairy-plant sludge had been applied for 4 years, heavy metal levels in both soil and plants were within European Union and Spanish legislative limits (Council of the European Communities Council Directive of 12 June 1986 on the protection of the environment, and in particular of the soil, when sewage sludge is used in agriculture (86/278/EEC), Official J. Eur. Communities 1986;L 181:6–12; Royal Decree 1310/1990, del 29 de octubre por el que se regula la utilizacion de los lodos de depuracion en el sector agrario, BOE 1990;262:32339–32340.) However, a number of significant metal-metal correlations (Ni–Zn, Ni–Cr, Ni–Cu, Cu–Cr, Zn–Cr and Pb–Cd) were detected in both the sludge and the sludge-amended soils, but not the non-amended soils, suggesting that the sludge is an important source of these metals. In addition, soils that had received the dairy-plant sludge had significantly higher conductivity, probably because of the NaOH used for cleaning in dairy plants. Salinity-related variables (K, NO3−) were significantly correlated with Cr and Zn concentrations in plant tissues. These findings suggest a need to assess the possible long-term effects of dairy sludge application, with the aim of developing guidelines for its use as a fertiliser.

Feasibility of vermicomposting dairy biosolids using a modified system to avoid earthworm mortality

A laboratory study was conducted to examine the feasibility of vermicomposting dairy biosolids (dairy sludge), either alone or with either of the bulking agents ‐ cereal straw or wood shavings, using the epigeic earthworm ‐ Eisinea andrei. Earthworms added directly to these three substrates died within 48 hours. A system was developed to overcome the toxic effect of unprocessed dairy biosolids. The substrates were placed over a layer of vermicomposted sheep manure into which the earthworms were inoculated. Within two weeks, all earthworms were within the upper layer of substrate. Compared to sheep manure which is a favourable substrate for vermicomposting, the three substrates containing dairy biosolids were more effective in supporting earthworm growth and reproduction. The final products obtained after 63 days of vermicomposting had 39–53% less organic carbon than the initial substrates. Organic fractionation indicated that vermicomposting increased the stability of the materials to biological decomposition. The vermicomposts obtained from the three substrates with dairy biosolids had low heavy metal contents and electrical conductivities, and did not inhibit plant growth when compared with a commercial vermicompost in a bioassay.