Correlation between phosphorus removal technologies and phosphorus speciation in sewage sludge: focus on iron-based P removal technologies.

Phosphorus recovery from sewage sludge as secondary raw materials or as a direct P-rich fertiliser is one of the top frontrunner solutions to tackle Phosphorus (P) scarcity and depletion. However, the efficiency of this P recovery process greatly depends on its phosphorus dissolution potential, which in return relies on the phosphorus speciation in the sewage sludge. This article investigates the potential correlation between P speciation in sewage sludge and the iron-based P removal technologies used in sewage treatment plants (STP) through an innovative sequential extraction method based on the SEDEX method that distinguishes quantitatively between ferrous bound phosphate and ferric bound phosphate. XRD and SEM-EDX were also used to characterise P and Fe species in the studied sludge qualitatively. Principal component analysis showed that the sludge characterised by P bound to ferric iron (as the dominant P fraction) are mostly correlated with sludge produced from the CPR process (chemical phosphorus removal) and primary sludge. Moreover, sludge with a non-negligible amount of P bound to ferrous iron were correlated with sludge from the mixed EBPR-CPR process (Enhanced Biological P Removal assisted with CPR). However, Vivianite was only found in CPR sludge with Fe/P molar ratio higher than 0.6.

Mechanisms governing the dissolution of phosphorus and iron in sewage sludge by the bioacidification process and its correlation with iron phosphate speciation.

In the last two decades, phosphorus (P) recovery from sewage sludge liquors gained much interest for its high-quality product potential. However, the consistently reported constraints are the low phosphorus availability and the technical-economical difficulties to increase it through chemical acidification. This article discusses the mechanisms of phosphorus dissolution by the biological acidification process (Biological acidification or acidic fermentation) as an alternative to chemical acidification. In addition, we investigate the potential correlation between the phosphorus dissolution and iron phosphate speciation of several types of sludge from different sewage treatment plants and P removal technologies. The results show that the percentage of P dissolution by bioacidification is always higher than the P dissolution by chemical acidification at equal pH for all types of sludge except for the settled primary sludge. The highest P dissolution was recorded for the sludge from the Enhanced Biological P Removal process assisted with Chemical P Removal process (EBPR-CPR) with around 65% of P dissolution. Three mechanisms were identified as contributing to the increased P dissolution by bioacidification: P release by the Polyphosphate Accumulating Organisms (PAO), P dissolution by pH decrease, and P dissolution by a biological activity at acidic pH (3.7-4) that includes iron reduction and aluminum dissolution. The principal component analysis and Pearson's correlation indicate that P dissolution by bioacidification is negatively correlated with the P-bound to ferric iron, hence positively correlated with the P-bound to ferrous iron, which characterizes the sludge from the EBPR-CPR process. This study suggests that the choice of the P removal technology significantly influences the P recovery from sewage sludge liquors.

Effect of starvation period on microbial community producing hydrogen from paperboard mill wastewater using anaerobic baffled reactor.

The aim of this study is to highlight the robustness and potentials of the anaerobic baffled reactor (ABR) configuration on keeping the microbial richness and diversity after starvation period of 7 days. The module at steady state operating conditions provided an average volumetric hydrogen production (VHP) of 0.2 ± 0.08 and 0.423 ± 0.5 l/d in the 1st and last compartment (C4). The VHP was gradually decreased from 0.2 to 0.003 l/d and from 0.423 to 0.1 l/d in compartments (C1 and C4) respectively during feed less period. However, the VHP was substantially increased up to 0.035 and 0.152 l/d in 1st (C1) and fourth compartment (C4) within 24 h, after reoperation of the ABR. Moreover, the H2 producers of Clostridiaceae, Ruminococcaceae, and Enterobacteriaceae families were dominant in the reactor after reoperation process. Quantitative polymerase chain reaction and next-generation sequencing methods results revealed that the microbial community structure was mainly composed of Proteobacteria, Firmicutes, Chloroflexi, Bacteroidetes, Planctomycetes, and Actinobacteria. The results showed the unique properties of the ABR configuration for keeping the microbial richness and diversity during feed less period.

Biochemical and microbial changes reveal how aerobic pre-treatment impacts anaerobic biodegradability of food waste.

Aerobic pre-treatment of food waste (FW) was performed at different oxygen concentrations (0%, 5%, 10% and 21%O2) and different durations (1, 2, 3 and 4 days) to investigate its impact on biochemical and microbial community characteristics of the waste and its ability to improve anaerobic biodegradability. Whatever the duration, the highest effect of pre-treatment was observed at full aerobic pre-treatment (21%O2) while 5%O2 and 10%O2 showed lower transformation performances. Biochemical variations at 21%O2 were mainly a decrease of simple carbohydrates, volatile fatty acids (VFA) and low molecular weight water soluble compounds and an increase of high weight water soluble compounds. Microbial community analysis showed a clear modification of populations after 21%O2 aerobic pre-treatment, changing from an initial dominance of lactic acid bacteria to a final dominance of VFA consumers (like Acetobacter) and a higher presence of Fungi. Enzymatic tests showed an increase of exoenzymes content and a higher presence of protein and carbohydrates degrading enzymes. Finally, the aerobic pre-treatment did not negatively impact methane potential of FW (496 NLCH4·kgVS-1) which remained unchanged after two days of pre-treatment at 21%O2. These latter optimal pre-treatment conditions are proposed to be tested in future investigation of anaerobic digestion (AD) process with low inoculum to substrate ratio in order to assess their ability to avoid acidification risk during AD of FW.

Physico-chemical, biochemical and nutritional characterisation of 42 organic wastes and residues from France.

The data presented in this article regroup characterisation of organic matter and nutritional composition of 42 organic wastes and residues usually used as substrates for anaerobic digestion. Those wastes have different origins from agro-industrial, agricultural and urban sectors in France including: algae, slaughterhouse waste, fat, food waste, fruits and vegetables residues, green waste, slurry, manure, wastewater treatment plant sludge and agricultural residues. The properties of organic matter are distinguished between global parameters (pH, total solids, volatile solids, COD and BMP), organic matter fractionation (biochemical and Van Soest) and the main nutrients content (N, P, K, Mg, Ca and S).

Dissolution of particulate phosphorus in pig slurry through biological acidification: A critical step for maximum phosphorus recovery as struvite.

Recycling phosphorus as struvite from pig slurry requires an acidification step to dissolve the inorganic solids containing most of the phosphorus. This study focused on the biological acidification of several pig slurries using sucrose as a model organic co-substrate. Lactic acid fermentation occurred systematically, dissolving 60-90% of TP (total phosphorus) and T-Mg (total magnesium) at pH 6 or lower. Optimal pH range for maximum P dissolution aimed at struvite recovery was 5.5-6. A simple model was developed correlating pH, sucrose and buffer capacity to optimize P dissolution and future recovery using real organic waste.

Understanding the anaerobic biodegradability of food waste: Relationship between the typological, biochemical and microbial characteristics.

In this study, an extensive characterisation of food waste (FW) was performed with the aim of studying the relation between FW characteristics and FW treatability through an anaerobic digestion process. In addition to the typological composition (paper, meat, fruits, vegetables contents, etc) and the physicochemical characteristics, this study provides an original characterisation of microbial populations present in FW. These intrinsic populations can actively participate to aerobic and anaerobic degradation with the presence of Proteobacteria and Firmicutes species for the bacteria and of Ascomycota phylum for the fungi. However, the characterisation of FW bacterial and fungi community shows to be a challenge because of the biases generated by the non-microbial DNA coming from plant and by the presence of mushrooms in the food. In terms of relations, it was demonstrated that some FW characteristics as the density, the volatile solids and the fibres content vary as a function of the typological composition. No direct relationship was demonstrated between the typological composition and the anaerobic biodegradability. However, the Pearson's matrix results reveal that the anaerobic biodegradation potential of FW was highly related to the total chemical oxygen demand (tCOD), the total solid content (TS), the high weight organic matter molecules soluble in water (SOLW>1.5 kDa) and the C/N ratio content. These relations may help predicting FW behaviour through anaerobic digestion process. Finally, this study also showed that the storage of FW before collection, that could induce pre-biodegradation, seems to impact several biochemical characteristics and could improve the biodegradability of FW.

Magnetite/graphene oxide nano-composite for enhancement of hydrogen production from gelatinaceous wastewater.

The effect of substrate to inoculum (So/Xo) ratio and supplementation of magnetite/graphene oxide (MGO) nano-composite material on hydrogen production from gelatinaceous wastewater via dark fermentation process was investigated. Results demonstrated that optimum So/Xo ratio of 1.0gCOD/gVSS achieved maximal hydrogen yield (HY) of 79.2±11.9mL H2/gCOD removed. Supplementation of anaerobes with 100mg/L MGO promoted HY up to 112.4±10.5mL H2/gCOD removed. Moreover, the degradation efficiency of carbohydrates, proteins and lipids was improved to 80.8±7.6, 34.4±2.3 and 31.4±2.2%, respectively. Acetate (HAc) and butyrate (HBu) concentrations increased from 102±6.8 to 125.3±6.3 and from 31.1±1.5 to 48.8±3.5mg/gVSS, respectively. However, propionate (HPr) concentration dropped from 35.9±2.7 to 15±1.3mg/gVSS. Hydrogenase enzyme activity increased 9-folds and the anaerobes elongated from ca. 1.8-2.9 to ca. 2.5-5.1µm with MGO addition. Moreover, Proteobacteria, Firmicutes, Clostridia and Bacilli were detected with the batches supplemented with MGO.

Characterizing the variability of food waste quality: A need for efficient valorisation through anaerobic digestion.

In order to determine the variability of food waste (FW) characteristics and the influence of these variable values on the anaerobic digestion (AD) process, FW characteristics from 70 papers were compiled and analysed statistically. Results indicated that FW characteristics values are effectively very variable and that 24% of these variations may be explained by the geographical origin, the type of collection source and the season of the collection. Considering the whole range of values for physicochemical characteristics (especially volatile solids (VS), chemical oxygen demand (COD) and biomethane potential (BMP)), FW show good potential for AD treatment. However, the high carbohydrates contents (36.4%VS) and the low pH (5.1) might cause inhibitions by the rapid acidification of the digesters. As regards the variation of FW characteristics, FW categories were proposed. Moreover, the adequacy of FW characteristics with AD treatment was discussed. Four FW categories were identified with critical characteristics values for AD performance: (1) the high dry matter (DM) and total ammonia nitrogen (TAN) content of FW collected with green waste, (2) the high cellulose (CEL) content of FW from the organic fraction of municipal solid waste, (3) the low carbon-to-nitrogen (C/N) ratio of FW collected during summer, (4) the high value of TAN and Na of FW from Asia. For these cases, an aerobic pre-treatment or a corrective treatment seems to be advised to avoid instabilities along the digestion. Finally, the results of this review-paper provide a data basis of values for FW characteristics that could be used for AD process design and environmental assessment.

Improving composting as a post-treatment of anaerobic digestate.

This work investigated the influences of practical parameters upon composting of digestate. The yardsticks for evaluation were digestate stabilization, nitrogenous emissions mitigation and self-heating potential. The results suggest choosing an "active" bulking agent like dry wood chips (WC) which served as free-water and nitrogen sink through composting. At an optimal volumetric WC:digestate mixing ratio of 4:1, nearly 90% of the initial NH4(+)/NH3 were fixed, which reduced significantly nitrogenous emissions. This mixing ratio also improved the stabilization and self-heating potential. Using small particle size WC increased narrowly O2 consumption and reduced NH3 emission. Storing used WC prior to recycling reduced 40% N2O emission compared to directly recycled WC. Recycling compost helped to decrease NH3 emission, but quadrupled N2O emission. The optimal aeration rate (15Lh(-1)kg OM0) which was lower compared to composting of organic waste, was enough to ensure the O2 supply and ameliorate the self-heating potential through composting of digestate.

Feasibility and interest of the anammox process as treatment alternative for anaerobic digester supernatants in manure processing--an overview.

Completely autotrophic nitrogen removal (ANR) is based on the combination of partial nitritation (PN) and anaerobic ammonium oxidation (anammox). It is a promising alternative for the subsequent treatment of biogas digester supernatants in livestock manure processing and nitrogen surplus scenarios. However, as no full-scale experiences in the treatment of manure digestates by ANR have been published to date, future field studies addressing treatment of this kind of effluent would be of great interest. Some topics to be considered in these studies would be coupling anaerobic digestion and ANR, analysis of the factors that affect the process, comparing reactor configurations, microbial ecology, gas emissions, and achieving robust performance. This paper provides an overview of published studies on ANR. Specific issues related to the applicability of the process for treating manure digestates are discussed. The energy requirements of ANR are compared with those of other technological alternatives aimed at recovering nitrogen from digester supernatants. The results of the assessment were shown to depend on the composition of the supernatant. In this regard, the PN-anammox process was shown to be more competitive than other alternatives particularly at concentrations of up to 2 kg NH4(+)-N m(-3).

Impact of biodegradation of organic matters on ammonia oxidation in compost.

Nitrification plays an important role in nitrogen turnover in composting process. It has been believed that nitrification occurs mainly during the maturation phase due to the elevated temperature during the active phase of composting. In this work, the intense biodegradation of organic matters is demonstrated to be another negative impact on the ammonia oxidation, the first step of nitrification. We investigated the ammonia oxidation in compost following organic matters addition at intermediate temperature. Different indicators of ammonia oxidation were studied, respectively. The accumulation of nitrite and nitrate was 10(2)-10(3) lower in composts with organic matters addition. The nitrous oxide emissions were absent or 40-fold inferior in these composts. The nitrogen mass balance indicated a less amount of oxidized ammonia after the addition. The ammonia-oxidizing bacteria declined following the organic matters addition. In contrast, the ammonia-oxidizing archaea were supported by the organic matters. Possible mechanisms of this impact were also discussed.

Prediction of hydrogen sulphide production during anaerobic digestion of organic substrates.

The main objective of this study was to develop a methodology to predict the hydrogen sulphide content of raw biogas produced during anaerobic mono-digestion of a bioenergy feedstock. Detailed chemical and biological analyses were made on 37 different feedstocks originating from urban wastewater treatment plants, farms, agri-food facilities and municipal wastes. Total sulphur content ranged from 1 to 29.6 mg S/kg of total solids, and 66% of the feedstocks analysed contained less than 5 mg S/kg of total solids. The biochemical methanogenic potential and biochemical biogas potential of each feedstock combined with its S content were used to predict appearance of H(2)S in the raw biogas. A model to link H(2)S in biogas with the carbon:sulphur ratio was established. Based on this model, a minimum carbon:sulphur ratio of 40 is required in feedstock to limit the concentration of hydrogen sulphide in raw biogas to less than 2% (volume/volume).

Homogeneity and synchronous dynamics of microbial communities in particulate biofilms: from major populations to minor groups.

Natural or engineered microbial populations often show variations over time. These variations may be due to environmental fluctuations or intrinsic factors. Thus, studying the dynamics of microbial diversity for different communities living in a spatially homogeneous landscape is of interest. As a model ecosystem, nitrifying biofilm communities were grown in a two litre inverse turbulent bed reactor (ITBR) containing an estimated 200 million small particles (about 150 µm in diameter). Each particulate biofilm is considered as a distinct community growing in the neighborhood of other similar particles, in a homogeneous and well-controlled environmental context. A molecular approach was adopted to test how microbial community structures might evolve: either in synchrony, converging or diverging. The shape of biofilm was observed by microscopy for each particle. The biomass content was evaluated by quantitative PCR and showed similar values for each particle. The microbial community structure was evaluated by Capillary Electrophoresis-Single Strand Conformation Polymorphism (CE-SSCP) fingerprinting and showed extraordinary homogeneity between particles, even though transitory community structures were observed when reactor operating conditions were modified. This homogeneity was observed for the Bacteria primer set but, more interestingly, was also observed when minor non-nitrifying bacteria making up the biofilm, representing about 5% and 10% of total cells, were targeted.

Changes in concentrations of fluoroquinolones and of ciprofloxacin-resistant Enterobacteriaceae in chicken feces and manure stored in a heap.

This study evaluated the impact of storing chicken manure on the degradation of enrofloxacin (ENR) and ciprofloxacin (CIP), and on the survival of CIP-resistant Enterobacteriaceae. At 24 d of age, half of 8900 chickens received ENR for 5 d. After the animals departed, their manure was stored in two heaps for 63 d. Enterobacteriaceae were cultured on media containing 0 to 32 mg L⁻¹ of CIP. A total of 320 isolates were fingerprinted using enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) to evaluate community structure. Initial concentrations of ENR and CIP in the heap were 22 and 1.8 mg kg⁻¹, respectively. Seventy-three percent of the two fluoroquinolones were eliminated during storage. The administration of ENR led to a 5.1 log₋10 decrease in Enterobacteriaceae concentrations and emergence of CIP-resistant bacteria, which became dominant in the feces. concentrations decreased 1.2 to 2.3 log₋10 2 d after the heaps were made and continued to decline during storage. No resistant were found by Day 63. The highest CIP minimum inhibitory concentration (MIC) values observed among isolates of and of both and sp. were 128 and 4 mg L⁻¹, respectively. The dominant ERIC-PCR profiles changed over time. There was no relationship between genotype and resistance-isolated strains to CIP. Storing chicken manure in heaps appeared to be an effective way of limiting the entrance of CIP-resistant E. coli into the environment but did not prevent the dissemination of fluoroquinolones after land spreading.

Nitrification and microbiological evolution during aerobic treatment of municipal solid wastes.

Nitrification is a key step in the nitrogen cycle in various ecosystems. In this study, the nitrogen dynamic and the evolution of groups of microorganisms were studied during aerobic treatment of fine organic fraction of municipal solid wastes. Mineralization of organic nitrogen exhibited two phases and resulted in two ammonia emissions peaks. The nitrogen balance indicated the onset of nitrification only during the maturation stage, which was confirmed by the accumulations of both nitrite and nitrate and the nitrous oxide emissions in this period. A significant development of ammonia-oxidizing bacteria correlated to the onset of nitrification. On the contrary, ammonia-oxidizing archaea were less abundant and declined through treatment. Identification of these ammonia oxidizers indicates that the Nitrosomonas europaea/eutropha-like ammonia oxidizing bacteria were responsible for ammonia oxidation instead of other groups of ammonia oxidizers during aerobic treatment of fine organic fraction of municipal solid wastes.

Fate of steroid hormones and endocrine activities in swine manure disposal and treatment facilities.

Manure may contain high concern endocrine-disrupting compounds (EDCs) such as steroid hormones, naturally produced by pigs, which are present at µgL(-1) levels. Manure may also contain other EDCs such as nonylphenols (NP), polycyclic aromatic hydrocarbons (PAHs) and dioxins. Thus, once manure is applied to the land as soil fertilizer these compounds may reach aquifers and consequently living organisms, inducing abnormal endocrine responses. In France, manure is generally stored in anaerobic tanks prior spreading on land; when nitrogen removal is requested, manure is treated by aerobic processes before spreading. However, little is known about the fate of hormones and multiple endocrine-disrupting activities in such manure disposal and treatment systems. Here, we determined the fate of hormones and diverse endocrine activities during manure storage and treatment by combining chemical analysis and in vitro quantification of estrogen (ER), aryl hydrocarbon (AhR), androgen (AR), pregnane-X (PXR) and peroxysome proliferator-activated γ (PPARγ) receptor-mediated activities. Our results show that manure contains large quantities of hormones and activates ER and AhR, two of the nuclear receptors studied. Most of these endocrine activities were found in the solid fraction of manure and appeared to be induced mainly by hormones and other unidentified pollutants. Hormones, ER and AhR activities found in manure were poorly removed during manure storage but were efficiently removed by aerobic treatment of manure.

Evaluation of Lactobacillus sobrius/L. amylovorus as a new microbial marker of pig manure.

Based on a comparison of the dominant microbial populations in 17 pig manure samples and using a molecular typing method, we identified a species, Lactobacillus sobrius and Lactobacillus amylovorus (which now are considered a single species and are designated L. sobrius/amylovorus here), that was consistently found in manure. The aim of the present study was to confirm by real-time PCR the relevance of this species as a marker of pig fecal contamination. The specificity of L. sobrius/amylovorus was evaluated in human and animal DNA extracted from feces. The real-time PCR assay then was applied to water samples, including effluents from urban wastewater treatment plants, runoff water, and rivers. L. sobrius/amylovorus was consistently present in all samples of swine origin: 48 fecal samples, 18 from raw manure and 10 from biologically treated manure at mean concentrations of 7.2, 5.9, and 5.0 log(10) cells/g, respectively. The species was not detected in any of the other livestock feces (38 samples from cattle and 16 from sheep), in the 27 human fecal samples, or in the 13 effluent samples from urban wastewater treatment plants. Finally, L. sobrius/amylovorus was not detected in runoff water contaminated by cattle slurry, but it was quantified at concentrations ranging from 3.7 to 6.5 log(10) cells/100 ml in runoff water collected after pig manure was spread on soil. Among the stream water samples in which cultured Escherichia coli was detected, 23% tested positive for L. sobrius/amylovorus. The results of this study indicate that the quantification of L. sobrius/amylovorus using real-time PCR will be useful for identifying pig fecal contamination in surface waters.

Pig manure contamination marker selection based on the influence of biological treatment on the dominant fecal microbial groups.

The objective of this study was to identify a microbial marker for pig manure contamination. We quantified the persistence of four dominant bacterial groups from the pig intestinal tract throughout manure handling at 10 livestock operations (including aerobic digestion) by using molecular typing. The partial 16S rRNA genes of Bacteroides-Prevotella, Eubacterium-Clostridiaceae, Bacillus-Streptococcus-Lactobacillus (BSL), and Bifidobacterium group isolates were amplified and analyzed by capillary electrophoresis single-strand conformation polymorphism. The most dominant bacterial populations were identified by cloning and sequencing their 16S rRNA genes. The results showed that Bifidobacterium spp. and, to a lesser extent, members of the BSL group, were less affected by the aerobic treatment than either Eubacterium-Clostridiaceae or Bacteroides-Prevotella. Two Bifidobacterium species found in raw manure were still present in manure during land application, suggesting that they can survive outside the pig intestinal tract and also survive aerobic treatment. The 16S-23S rRNA internal transcribed spacer of one species, Bifidobacterium thermacidophilum subsp. porcinum, was sequenced, and a specific pair of primers was designed for its detection in the environment. With this nested PCR assay, this potential marker was not detected in samples from 30 bovine, 30 poultry, and 28 human fecal samples or in 15 urban wastewater effluents. As it was detected in runoff waters after spreading of pig manure, we propose this marker as a suitable microbial indicator of pig manure contamination.

Livestock waste treatment systems for environmental quality, food safety, and sustainability.

The intensification of livestock operations has benefited production efficiency but has introduced major environmental issues, becoming a concern in both developed and developing countries. The aim of this paper is primarily to address the impact of the livestock sector on environmental pollution (ammonia, greenhouse gases and pathogens), evaluate the related health risks and, subsequently, assess the potential role of waste treatment systems in attenuating these environmental and health issues. This paper is a collection of data pertaining to world trends in livestock production, since the mid 1990s and intensive livestock farming practices along with their impact on: water pollution by nitrates and through eutrophication; air pollution, particularly ammonia and greenhouse gases emissions, and soil pollution because of nutrient accumulation. Finally, this paper examines some of the benefits of treating livestock manures, issues related to the adoption of treatment systems by livestock operations and current as well as past technological developments.