Quantification of Salmonella spp. in composted biosolids using a TaqMan qPCR assay

Composting is increasingly used to transform biosolids, obtained following wastewater treatment, into a more stable organic product that can be released in the environment. The process must however be closely monitored to assure that the end product meets the regulations set by environmental agencies with regards to the amount of pathogenic microorganisms present. In this study, a TaqMan qPCR approach targeting the invA gene was developed to monitor the presence of Salmonella spp. in composted biosolids. A validation step was first performed to evaluate the effect of compost age on the quantification of various concentrations of seeded Salmonella typhimurium. Secondly, qPCR was used to investigate the effect of composting time, varying from 1 month to 24 months, on the presence of Salmonella spp. naturally present in biosolids samples. Culture media were used in parallel to corroborate the results obtained by qPCR. The detection limit of the invA gene obtained experimentally from composts seeded with S. typhimurium was 5.8 copies or the equivalent of 5.8 CFU per qPCR reaction. Although the results indicated that compost age had a marginal effect on the detection of seeded S. typhimurium, the TaqMan qPCR approach was efficient at detecting and quantifying the amount of Salmonella spp. present in naturally contaminated composted biosolids of different ages. Results showed that there was a significant decrease in the amount of Salmonella DNA present in composted biosolids over time, which was also corroborated by the CFU counts obtained on the BSA culture medium. However, qPCR was more specific, robust and rapid to execute than performing counts on culture media. qPCR shows promise for routine examination of composted biosolids to ascertain that pathogenic microorganisms, including Salmonella spp., are decreased below acceptable limits before their application in the environment.     

Nutritional status of different biosolids and their impact on various growth parameters of wheat (Triticum aestivum L.)

Biosolids can be effectively recycled and applied as soil amendments for agricultural crops because they contain several important micro and macronutrients including nitrogen, phosphorus, potassium, manganese. In the current study, we evaluated the effectiveness of seven biosoilds on different growth parameters of wheat crop. The biosolids used were lime stabilized, composted, liquid mesophilic anaerobically digested (liquid MAD), thermally dried mesophilic anaerobically digested (thermally dried MAD), thermally hydrolyzed mesophilic anaerobically digested (thermally hydrolysed MAD), dewatered mesophilic anaerobically digested (dewatered MAD) and thermally dried raw biosolids. We also analysed biosolids for their nutrient contents before application. The results revealed that different types of biosolids differed in nitrogen and phosphorous contents with highest contents observed in dewatered (5.70% nitrogen, 2.32% phosphorous) and liquid biosolids (2.35% phosphorous). The plant height, plant diameter and dry weight yield of wheat was increased with the increase in concentrations of biosolids. Liquid MAD resulted in maximum plant height of 120.35 ± 3.23, 133.2 ± 3.67 and 147.25 ± 3.11 at 3.33, 6.66 and 9.99 tons/ha concentration. The highest plant diameter was recorded (1.05–1.45 cm) where mineral nitrogen was applied. The study will be helpful in replacing the synthetic fertilizer with biosolids to fulfil the nutritional requirements of agricultural crops.     

Toxic effects of digested, composted and thermally-dried sewage sludge on three plants

In order to evaluate potential toxic effects of stabilized sewage sludge that are currently applied to agricultural soils, three types of municipal sewage sludge and one pig slurry were subjected to phytotoxicity assays using three plants (Brassica rapa, Lolium perenne and Trifolium pratense). Equivalent batches of aerobically and anaerobically-digested sludge (F) from two municipal wastewater treatment plants, were composted (C) or thermally dried (T). In addition, one anaerobically-digested and thermally-dried pig slurry (P) was tested. A seedling growth test was performed in accordance with the OECD Guideline 208A, using seed emergence and shoot length as endpoints to identify the inhibition of plants growing in increasing doses of sludge. A correlation analysis between EC50 and physico-chemical parameters or the pollutant burden of the biosolids was also calculated. In all tests, lower germination rates were observed for T. pratense than for L. perenne and B. rapa. A moderate stimulatory effect on shoot length at low doses was observed for the three plants. In these wastes, a strong positive correlation was found between higher values of EC50 (less toxicity) and the stability degree of their organic matter, and a negative correlation between EC50 and total N, hydrolysable N or NH4-N content. No correlations were found with heavy metal or organic pollutant content in those wastes. Results indicate that digested sludge, thermally-dried sludge and thermally-dried pig slurry have non-negligible short term phytotoxic effects, and confirm that composting is an effective sludge treatment for the reduction of phytotoxicity.     

Life-Cycle Assessment of Biosolids Processing Options

Biosolids, also known as sewage sludge, are reusable organic materials separated from sewage during treatment. They can be managed in a variety of ways. Different options for biosolids handling in Sydney, Australia, are compared in this study using life-cycle assessment. Two key comparisons are made: of system scenarios (scenario 1 is local dewatering and lime amendment; scenario 2 is a centralized drying system) and of technologies (thermal drying versus lime amendment). The environmental issues addressed are energy consumption, global warming potential (GWP), and human toxicity potential (HTP).
Scenario 2 would consume 24% more energy than scenario 1. This is due to the additional electricity for pumping and particularly the petrochemical methane that supplements biogas in the drier. A centralized system using the same technologies as scenario 1 has approximately the same impacts. The GWP and HTP of the different scenarios do not differ significantly.
The assessment of technology choices shows significant differences. The ample supply of endogenous biogas at North Head sewage treatment plant for the drying option allows reductions, relative to the lime-amendment option, of 68% in energy consumption, 45% in GWP, and 23% in HTP.
Technology choices have more significant influence on the environmental profile of biosolids processing than does the choice of system configurations. Controlling variables for environmental improvement are the selection of biogas fuel, avoidance of coalsourced electrical energy, minimization of trucking distances, and raising the solids content of biosolids products.     

Field investigations on the survival of Escherichia coli and presence of other enteric micro-organisms in biosolids-amended agricultural soil

AIMS: To measure the survival of enteric micro-organisms in agricultural soil amended with conventional and enhanced treated biosolids in relation to environmental and edaphic conditions. METHODS AND RESULTS: Escherichia coli, Salmonella and F-specific RNA bacteriophage were enumerated in sludge and amended soil. Salmonella was not detected and only small numbers of bacteriophages were found in conventional, dewatered mesophilic anaerobically digested biosolids (DMAD). Neither organism was detected in soil. Escherichia coli numbers in soil increased with DMAD application compared with the unamended control, or soil receiving enhanced treated, thermally dried digested (TDD) and composted (CPT) biosolids. Empirical statistical models were developed summarizing the relationship between soil temperature, moisture content and time and E. coli populations. Background numbers of E. coli declined with increasing soil temperature and decreasing soil moisture responding to seasonal patterns in environmental conditions. Time following application was the only significant explanatory variable of E. coli numbers and decay in DMAD-amended soil. CONCLUSIONS: E. coli are an indigenous component of the microbial community in field soil and populations increased in cool, moist soil during autumn-winter and declined in warm, dryer soil during spring-summer. Enhanced treated biosolids were not a source of E. coli, but reduced the size of the indigenous population possibly by stimulating the activity of predatory and competing soil flora because of the organic substrate input from sludge. Conventionally treated biosolids increased E. coli numbers in soil. However, introduced bacteria declined rapidly and survival was limited to 3 months, irrespective of the timing of sludge application or environment. SIGNIFICANCE AND IMPACT OF THE STUDY: The results provide assurance that residual numbers of pathogens applied to soil in treated biosolids decay to background values well within cropping and harvesting restrictions imposed when sewage sludge is spread on farmland.     

LCA application to integrated waste management planning in Gipuzkoa (Spain)

Goal, Scope and Background  Gipuzkoa is a department of the Vasque Country (Spain) with a population of about 700,000 people. By the year 2000 approximately 85% of municipal solid waste in this area was managed by landfilling, and only 15% was recycled. Due to environmental law restrictions and landfill capacity being on its limit, a planning process was initiated by the authorities. LCA was used, from an environmental point of view, to assess 7 possible scenarios arising from the draft Plan for the 2016 time horizon. Main Features  In each scenario, 9 waste flows are analysed: rest waste, paper and cardboard, glass containers, light packaging, organic-green waste, as well as industrial/commercial wood, metals and plastics, and wastewater sludge. Waste treatments range from recycling to energy recovery and landfilling. Results  Recycling of the waste flows separated at the source (paper and cardboard, glass, light packaging, organic-green waste, wood packaging, metals and plastics) results in net environmental benefits caused by the substitution of primary materials, except in water consumption. These benefits are common to the 7 different scenarios analysed. However, some inefficiencies are detected, mainly the energy consumption in collection and transport of low density materials, and water consumption in plastic recycling. The remaining flows, mixed waste and wastewater sludge, are the ones causing the major environmental impacts, by means of incineration, landfilling of partially stabilised organic material, as well as thermal drying of sludge. With the characterisation results, none of the seven scenarios can be clearly identified as the most preferable, although, due to the high recycling rates expected by the Plan, net environmental benefits are achieved in 9 out of 10 impact categories in all scenarios when integrated waste management is assessed (the sum of the 9 flows of waste). Finally, there are no relevant differences between scenarios concerning the number of treatment plants considered. Nevertheless, only the effects on transportation impacts were assessed in the LCA, since the plant construction stage was excluded from the system boundaries. Conclusions  The results of the study show the environmental importance of material recycling in waste management, although the recycling schemes assessed can be improved in some aspects. It is also important to highlight the environmental impact of incineration and landfilling of waste, as well as thermal drying of sludge using fossil fuels. One of the main findings of applying LCA to integrated waste management in Gipuzkoa is the fact that the benefits of high recycling rates can compensate for the impacts of mixed waste and wastewater sludge. Recommendations and Outlook  Although none of the scenarios can be clearly identified as the one having the best environmental performance, the authorities in Gipuzkoa now have objective information about the future scenarios, and a multidisciplinary panel could be formed in order to weight the impacts if necessary. In our opinion, LCA was successfully applied in Gipuzkoa as an environmental tool for decision making.     

Life Cycle Environmental and Cost Impacts of Using an Algal Turf Scrubber to Treat Dairy Wastewater

Using algae to simultaneously treat wastewater and produce energy products has potential environmental and economic benefits. This study evaluates the life cycle energy, greenhouse gas (GHG) emissions, eutrophication potential, and cost impacts of incorporating an algal turf scrubber (ATS) into a treatment process for dairy wastewater. A life cycle inventory and cost model was developed to simulate an ATS treatment system where harvested algae would be used to generate biogas for process heat and electricity generation. Modeling results show that using an ATS significantly reduces eutrophication impacts by reducing chemical oxygen demand, nitrogen, and phosphorus in the wastewater. With low water recirculation rates through the ATS and high algae productivity, inclusion of the ATS results in net energy displacement and a reduction of GHG emissions compared to a system with no ATS. However, if high water recirculation rates are used or if algae biosolids from the digester are dried, the system results in a net increase in energy consumption and GHG emissions. The life cycle treatment cost was estimated to be $1.42 USD per cubic meter of treated wastewater. At this cost, using an ATS would only be cost effective for dairies if they received monetary credits for improved water quality on the order of $3.83 per kilogram of nitrogen and $9.57 per kilogram of phosphorus through, for example, nutrient trading programs.     

Life cycle assessment of different reuse percentages for glass beer bottles

Life cycle assessment (LCA) is increasingly becoming an important tool for ecological evaluation of products or processes. In this study the environmental impacts associated with the returnable and the non-returnable glass beer bottles were assessed in order to compare different reuse percentages. The inventory analysis is performed with data obtained from two Portuguese companies (a glass bottles producer and a brewery) and completed with the BUWAL database. It includes all operations associated with the bottles’ manufacture, the brewery and the wastewater treatment plant. The environmental impact assessment considers both the potential ecological and ecotoxicological effects of the emissions. The environmental impact categories included and discussed in this study are the contribution to ecological and human health, global warming, stratospheric ozone depletion, acidification, eutrophication and photochemical ozone creation. The first category is divided into three subcategories that are human toxicity, critical air volume and critical water volume. This study was performed for several reuse percentages and returnable bottle cycles, and is comprised of a sensitivity analysis. The general output is that the relative importance of the impacts associated with the use of returnable and/or non-returnable bottles depends on the number of cycles performed by the returnable bottles. According to the impact index defined in this study, the most significant impacts are the eutrophication and the final solid wastes generated, and the least significant impact is the ozone depletion.     

Evaluation of “Classic” and Emerging Contaminants Resulting from the Application of Biosolids to Agricultural Lands: A Review

The presence of detectable amounts of contaminants in treated sewage sludge (concentrations μg/kg – mg/kg) has led to concerns that land applications of biosolids may result in an accumulation of contaminants in the soil and their subsequent translocation through the food chain. Despite advances in wastewater management (e.g., anaerobic, thermophilic, and mesophilic digestion), many compounds and their metabolites remain intact following treatment. This review looks at the main risk factors relating to the occurrence of “classic” (persistent organic pollutants [POPs]) and emerging pollutants (pharmaceuticals and personal care products) in biosolids. Relevant EU legislation and risk assessment strategies for the control of emerging contaminants are also considered. Organic pollutants regulated under the Stockholm Convention on POPs along with PPCPs were identified as contaminants of concern based on the risk factors: persistence, bioaccumulation, and toxicity (PBT). PPCPs were recognized as being of particular concern as their high transformation/removal rates are compensated by their continuous introduction into the environment. This study highlights the growing concern in relation to emerging contaminants in biosolids and highlights risk assessment strategies that can be used to characterize potential human/environmental risks.     

Organic amendment additions to rangelands: A meta‐analysis of multiple ecosystem outcomes

Interest in land application of organic amendments—such as biosolids, composts, and manures—is growing due to their potential to increase soil carbon and help mitigate climate change, as well as to support soil health and regenerative agriculture. While organic amendments are predominantly applied to croplands, their application is increasingly proposed on relatively arid rangelands that do not typically receive fertilizers or other inputs, creating unique concerns for outcomes such as native plant diversity and water quality. To maximize environmental benefits and minimize potential harms, we must understand how soil, water, and plant communities respond to particular amendments and site conditions. We conducted a global meta‐analysis of 92 studies in which organic amendments had been added to arid, semiarid, or Mediterranean rangelands. We found that organic amendments, on average, provide some environmental benefits (increased soil carbon, soil water holding capacity, aboveground net primary productivity, and plant tissue nitrogen; decreased runoff quantity), as well as some environmental harms (increased concentrations of soil lead, runoff nitrate, and runoff phosphorus; increased soil CO₂ emissions). Published data were inadequate to fully assess impacts to native plant communities. In our models, adding higher amounts of amendment benefitted four outcomes and harmed two outcomes, whereas adding amendments with higher nitrogen concentrations benefitted two outcomes and harmed four outcomes. This suggests that trade‐offs among outcomes are inevitable; however, applying low‐N amendments was consistent with both maximizing benefits and minimizing harms. Short study time frames (median 1–2 years), limited geographic scope, and, for some outcomes, few published studies limit longer‐term inferences from these models. Nevertheless, they provide a starting point to develop site‐specific amendment application strategies aimed toward realizing the potential of this practice to contribute to climate change mitigation while minimizing negative impacts on other environmental goals.     

Movement of water and heavy metals (Zn, Cu, Pb and Ni) through sand and sandy loam amended with biosolids under steady-state hydrological conditions

New guidelines for using biosolids in UK agriculture favour the use of enhanced treated biosolids, such as dried and composted cakes, due to concerns about the potential for transfer of pathogens into the food chain. However, there is a need to ensure that their use is environmentally acceptable and does not increase the risk to potable water supplies or the food chain from other contaminants such as heavy metals and xenobiotic organic chemicals. The objective of this study was to determine whether the use of composted and dried mesophilic anaerobically digested dewatered (MADD) biosolids would increase the risk of heavy metal leaching from cultivated horizons when compared to more conventionally used MADD cake. Three biosolids (MADD sewage sludge cake - fresh, dried and composted) were mixed with a sand (typic quartzipsamments, %OM = 3.0, pH = 6.5) or a sandy loam (typic hapludalf, %OM = 4.8, pH = 7.6) at an application rate equivalent to 250 kg N/ha/y resulting in loadings of approximately Zn: 6 microg, Cu: 2 microg, Pb: 5 microg and Ni: 0.2 microg/g of soil dry weight basis. These amended soils were repacked into columns (0.4 m by 0.1 m internal diameter) and leaching of Zn, Cu, Pb and Ni was investigated following application of two 24 h simulated rainfall events of 4.5 mm/h. Water balance data and the use of conservative tracers (Cl- and Br ) showed that the hydrological regimes of each core were comparable and, thus, unlikely to account for differences in metal leaching observed. Although no significant difference (P = 0.05) was observed between biosolid amended and control soils, those amended with composted sludge consistently gave higher loss of all metals than did the control soils. Total losses of metals from compost amended soil over the two rainfall events were in the ranges, Zn:20.5-58.2, Cu:9.0-30.5, Pb:24.2-51.2 and Ni:16.0-39.8 microg metal/kg amended soil, compared with Zn:16.4-41.1, Cu:6.2-25.3, Pb:16.9-41.7, and Ni:3.7-25.4 microg metal/kg soil from the control soils. Losses of Zn, Cu, Pb and Ni from fresh MADD cake amended soils (19.8-41.3, 3.2-25.8, 21.6-51.6 and 7.6-36.5 microg metal/kg amended soil, respectively) and from dry MADD cake amended soils (10.7-36.7, 1.8-23.8, 21.2-51.2 and 6.8-39.2 microg metal/kg amended soil, respectively) were similar to the controls. Generally, quantities of metals leached followed the order Zn = Pb > Cu > Ni, which was consistent with the levels of metals in the original sludge/soil mixtures. These results suggest that composting or drying MADD biosolids is unlikely to increase the risk of groundwater contamination when compared to the use of MADD cake; therefore, the changes in UK sludge use in agriculture guidelines are satisfactory in this respect.     

Using Life-Cycle Assessment in Process Design

This article presents the application of life-cycle assessment in early phases of process design in the context of technology that employs a bio-based material. The goal is to identify hot spots in the process chains with regard to environmental impacts by performing a dominance analysis. By focusing his activities on the hot spots identified, the designer is given the opportunity to efficiently improve environmental performance. This approach is illustrated for the case of supercritical water gasification, a novel technology for the treatment of organic feedstock with high moisture content. In the reactor under supercritical conditions, organic components are converted into a high-caloric synthesis gas, with hydrogen, methane, and carbon dioxide as the main products. The data used for the assessment are obtained from laboratory tests and the literature, completed by assumptions for missing data. The scope of assessment ranges from the extraction of raw materials to the product, that is, hydrogen (cradle to gate) with sewage sludge of a municipal wastewater treatment plant used as feedstock. The assessment identifies the main sources of environmental impacts. The predominant process step in terms of global warming potential is the supply of the gasification process with additional heat. The production of a blending agent in the dewatering step is the main source of the impact category of acidification, whereas the wastewater treatment plant is the origin of emissions that lead to eutrophication. The revealed sources are analyzed further and options for reducing the environmental impacts are discussed.     

qPCR quantification and genetic characterization of Clostridium perfringens populations in biosolids composted for 2 years

Aim: The ability of Clostridium perfringens to survive for a long time in the environment makes it a suitable indicator of faecal pollution, but its use as a routine indicator organism in biosolids and composted biosolids has not yet been adopted. This study was performed to improve our understanding of C. perfringens persistence in composted biosolids by monitoring its presence and studying its genetic diversity. Methods and Results: A culture‐independent TaqMan qPCR assay targeting the cpn60 gene was adapted to enumerate C. perfringens in composted biosolid samples varying in age from 1 to 24 months. The pathogen was detected in all compost samples under study, but no correlation between composting time and number of cpn60 copies was observed. Rep‐PCR detected 14 different C. perfringens genotypes, all belonging to toxinotype A, which is the most common biotype found in human and animal gastrointestinal tracts. Conclusions: Composting did not significantly decrease the number of C. perfringens cells. High genetic diversity of C. perfringens isolates present in composted biosolids is reported for the first time. Significance and Impact of Study: This study evaluated tools for surveillance of composting processes, source tracking and risk assessment of composted biosolids.     

Efficacy of lime, biosolids, and mycorrhiza for the phytostabilization of sulfidic copper tailings in Chile: a greenhouse experiment

Inadequate abandonment of copper mine tailings under semiarid Mediterranean climate type conditions has posed important environmental risks in Chile due to wind and rain erosion. There are cost-effective technologies for tailings stabilization such as phytostabilization. However, this technology has not been used in Chile yet. This study evaluated in a greenhouse assay the efficacy of biosolids, lime, and a commercial mycorrhiza to improve adverse conditions of oxidized Cu mine tailings for adequate establishment and grow of Lolium perenne L. var nui. Chemical characterization of experimental substrates and pore water samples were performed; plant density, biomass production, chlorophyll content, and metal content in shoots was evaluated in rye grass plants after an eight-week growth period. Results showed that neutralization of tailings and superficial application of biosolids increased both aerial biomass production and chlorophyll content of rye grass. Increased Cu solubilization and translocation to shoots occurred after biosolids application (mixed), particularly on unlimed tailings, due to formation of soluble organometallic complexes with dissolved organic carbon (DOC) which can be readily absorbed by plant roots. Positive effects of mycorrhizal inoculation on rye grass growth were restricted to treatments with superficial application of biosolids, probably due to Cu toxicity effects on commercial mycorrhiza used (Glomulus intraradices).     

Organic and inorganic fertilizer effects on a degraded Patagonian rangeland

The forest-steppe ecotone in NW Patagonia is a semiarid ecosystem affected by natural and anthropogenic fires, and overgrazing by sheep. Following a wild fire in the driest portion of this ecotone, a 3-year study was conducted to assess the impacts of a single application of inorganic and organic fertilizers on soil and vegetation recovery. Organic fertilizers were composts derived from biosolids and municipal solid wastes. Six treatments were evaluated: screened and unscreened biosolids compost and municipal solid wastes compost (40 Mg ha^?1), inorganic fertilizer (100 kg N and 35 kg P ha^?1), and no application. Soils were chemically characterized, and soil microbial activity was assessed as potential respiration and N-mineralization. Vegetation responses included plant cover, composition, phytomass, and N resorption prior to abscission, and leaf litter quality of the dominant species. Organic fertilizers increased soil organic matter, nutrients and microbial activity. Plant cover and aboveground phytomass, dominated by the native perennial tussock grass Poa ligularis, showed a higher increase with inorganic than with organic fertilization. While vegetation responded more to inorganic fertilizer, due to its higher initial pulse of available N, organic fertilizers had a positive impact on soil chemical and biological properties.     

Use of a Battery of Chemical and Ecotoxicological Methods for the Assessment of the Efficacy of Wastewater Treatment Processes to Remove Estrogenic Potency

Endocrine Disrupting Compounds pose a substantial risk to the aquatic environment. Ethinylestradiol (EE2) and estrone (E1) have recently been included in a watch list of environmental pollutants under the European Water Framework Directive. Municipal wastewater treatment plants are major contributors to the estrogenic potency of surface waters. Much of the estrogenic potency of wastewater treatment plant (WWTP) effluents can be attributed to the discharge of steroid estrogens including estradiol (E2), EE2 and E1 due to incomplete removal of these substances at the treatment plant. An evaluation of the efficacy of wastewater treatment processes requires the quantitative determination of individual substances most often undertaken using chemical analysis methods. Most frequently used methods include Gas Chromatography-Mass Spectrometry (GCMS/MS) or Liquid Chromatography-Mass Spectrometry (LCMS/MS) using multiple reaction monitoring (MRM). Although very useful for regulatory purposes, targeted chemical analysis can only provide data on the compounds (and specific metabolites) monitored. Ecotoxicology methods additionally ensure that any by-products produced or unknown estrogenic compounds present are also assessed via measurement of their biological activity. A number of in vitro bioassays including the Yeast Estrogen Screen (YES) are available to measure the estrogenic activity of wastewater samples. Chemical analysis in conjunction with in vivo and in vitro bioassays provides a useful toolbox for assessment of the efficacy and suitability of wastewater treatment processes with respect to estrogenic endocrine disrupting compounds. This paper utilizes a battery of chemical and ecotoxicology tests to assess conventional, advanced and emerging wastewater treatment processes in laboratory and field studies.     

A Life Cycle Assessment on the Dehairing of Rawhides: Chemical Treatment versus Enzymatic Recovery through Solid State Fermentation

The leather industry needs to switch from the traditional chemically based dehairing process to an environmentally friendly one so that the overall burdens to the environment are reduced. The primary goal of the work was thus to compare the chemical leather dehairing process to an enzymatically based one using the enzymes that are extracted after the application of solid state fermentation (SSF) on hair wastes generated after dehairing. The environmental burdens of the dehairing stage were determined using a life cycle assessment (LCA) approach by comparing the two aforementioned management scenarios. The first scenario was the commonly used technology in which hair is removed via a chemical process and then composted in open piles. This scenario included two subscenarios where hair waste is either incinerated or landfilled. In the second scenario, the proteolytic enzymes extracted during the SSF of the residual hair are used to dehair the new rawhides instead of chemicals. Industrial and laboratory data were combined with international databases using the SimaPro 8.0 LCA software to make comparisons. The environmental impacts associated with the enzymatic dehairing were significantly lower than the ones associated to the conventional chemical dehairing process. This difference is attributed to the impacts associated with the original production of the chemicals and to the electricity consumed in the conventional method. A sensitivity analysis revealed that the results are affected by the amounts of chemicals used during dehairing.     

Molecular pathogen detection in biosolids with a focus on quantitative PCR using propidium monoazide for viable cell enumeration

Sewage sludge is the solid, organic material remaining after wastewater is treated and discharged from a wastewater treatment plant. Sludge is treated to stabilize the organic matter and reduce the amount of human pathogens. Once government regulations are met, including material quality standards (e.g., E. coli levels and heavy metal content) sludge is termed “biosolids”, which may be disposed of by land application according to regulations. Live-culture techniques have traditionally been used to enumerate select pathogens and/or indicator organisms to demonstrate compliance with regulatory requirements. However, these methods may result in underestimates of viable microorganisms due to several problems, including their inability to detect viable but non-culturable (VBNC) cells. Real-time quantitative polymerase chain reaction (qPCR) is currently under investigation as a fast, sensitive, and specific molecular tool for enumeration of pathogens in biosolids. Its main limitation is that it amplifies all target DNAs, including that from non-viable cells. This can be overcome by coupling qPCR with propidium monoazide (PMA), a microbial membrane-impermeant dye that binds to extracellular DNA and DNA in dead or membrane-compromised cells, inhibiting its amplification. PMA has successfully been used to monitor the presence of viable pathogens in several different matrices. In this review the use of PMA–qPCR is discussed as a suitable approach for viable microbial enumeration in biosolids. Recommendations for optimization of the method are made, with a focus on DNA extraction, dilution of sample turbidity, reagent concentration, and light exposure time.     

Life cycle assessment of side stream removal and recovery of nitrogen from wastewater treatment plants

In the light of a circular economy, the Nijhuis Ammonia Recovery system (AECO‐NAR) was developed to not only remove nitrogen from wastewater streams, but also produce ammonium sulfate (AS), used as fertilizer, in a single plant. The goal of this paper was to quantify the environmental impacts of side stream ammonia recovery with the AECO‐NAR system and compares them with the impacts of side stream nitrogen removal combined SHARON (partly nitrification)‐anammox plant. For this, an environmental life cycle assessment was performed with a functional unit (FU) of the treatment of 1 kg of total dissolved nitrogen inflow. Since AS obtained by the AECO‐NAR is a by‐product of the ammonia removal process, allocation was based on system expansion. Foreground inventory data were obtained from a full‐scale plant. ReCiPe2016 was used to determine human health and biodiversity impacts. Results show that due to the production of AS in an integrated water treatment and production system, the AECO‐NAR avoids impacts of current AS production, leading to negative impact scores. Impacts per FU decrease with increasing inflow concentrations of ammonia. Main improvement options are the use of renewable energy and the replacement of the cleaning chemical citric acid with a sustainable alternative. Total impacts of the AECO‐NAR system diminish when comparing the system to the biological SHARON‐Anammox system, due to production of AS fertilizer product. Due to the fertilizer production step being integrated in the side stream treatment, the complete system is beneficial over ammonia recovery and wastewater treatment as separate systems.     

Bench and full-scale studies for odor control from lime stabilized biosolids: the effect of mixing on odor generation

Lime stabilization is a means to raise the pH of biosolids to meet specific pathogen requirements. Along with controlling the microbial growth, lime stabilization reduces the potential for offensive odors. Lime stabilized biosolids can be beneficially used as a soil amendment and also for land reclamation. However, if biosolids are not properly incorporated with the lime, there is a potential for microbial growth, which consequently leads to the emanation of offensive odors and growth of pathogens. Proper mixing was found to be an important factor for the reduction of offensive odors in biosolids treatment. To better understand the effects of mixing on odorous products, bench-scale and full-scale tests were conducted to assess the lime stabilization process and investigate mixing quality at a wastewater treatment plant to help reduce odors associated with known odorants. The results of 4-week laboratory bench-scale tests showed that mixing had the largest effect on odor. The hedonic tone test of the control samples with poor mixing showed a hedonic tone of -2.9 initially and then dropped to -7.3 on Day 29. The hedonic tone of the 3.5%, 7%, and 10% lime mixed biosolids had similar hedonic tones (-2.8 to -2.5) on Day 1 and slightly fluctuated over time and ended at -1.6 to -2.7 on Day 29, which was less odorous than the controls. The control sample with poor mixing showed a rapid pH drop from 12.1 on Day 1 to 8.4 on Day 7. The pH of the control sample was considerably lower than the mixed samples and ended up on Day 28 with a pH of 8.0. The pH of the 7% and 10% samples were relatively stable throughout the 4-week period with a pH still higher than 12 on Day 28. The biosolids with better mixing had a less offensive odor and weaker odor strength than the controls collected at the plant with poor mixing. The lime stabilization process in the wastewater treatment plant was modified in a full-scale study by prolonging the mixing time. The samples collected from the modified process had a less offensive odor and weaker odor strength than the controls from the original lime addition process with short mixing time. The hedonic tone of the two biosolid samples taken from the modified process (-2.5 to -3.0) was less negative than the controls (-3.5 to -4.5). The pH of the biosolid samples taken from the modified process was still above 12 on Day 21, while the pH notably drooped in the controls from 11 on Day 1 to 7.5-8.5 on Day 7. In addition, headspace analysis from both bench and full-scale tests indicated that the sulfur compounds were more prominent in poorly mixed samples than well mixed samples.