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Dewatering of anaerobic digested (AD) sludge containing waste-activated sludge (WAS) from enhanced biological phosphorus removal (EBPR) poses numerous challenges including poor dewaterability, struvite scale formation, and recycling of high N and P levels in the sludge liquor to the treatment process. A full-scale water reclamation facility was investigated to mitigate these problems by experimenting with direct dewatering of EBPR WAS, bypassing the AD step. The investigations experimented with various blends of AD primary sludge with undigested thickened WAS to achieve dewatering performance improvements and overall operational cost savings. Direct thickened WAS dewatering has had many positive impacts including enhanced sludge cake solids concentration, reduced chemical use for facility operations, reduced struvite scaling, reduced biogas conditioning media servicing, eliminated need for centrate treatment, recovered capacity of existing unit operations including anaerobic digesters, and eliminated several proposed capital improvement projects that were previously deemed necessary. Although bypassing of WAS to AD reduced total biogas production, the specific gas yield increased to meet all of the facility's biogas demands and minimized excess gas flaring. The overall biosolids production mass increased causing increased transportation costs for disposal and caused notable odors, both of which are being currently investigated. PRACTITIONER POINTS: Direct WAS dewatering bypassing anaerobic digestion yields operational and process benefits in an EBPR water resource recovery facility Dewatered cake solids were increased compared with combined primary and WAS anaerobic digestion and dewatering Nutrient loads in sludge processing returns streams and operational costs are reduced by direct WAS dewatering.

Gari is a common cassava precooked dried semolina in sub‐Saharan Africa. Our study investigated the role of process parameters and mash water content on gari quality during traditional roasting stage. The statistical analysis for eight quality criteria revealed that gari quality is highly influenced by the process parameters adopted by the operators. To emphasise the twin impact of roasting parameters and mash water content, different mashes with varying water content were roasted leading to different adjustments of the roasting conditions according to the operators. When the variability of the water content becomes greater, a greater variability in the final quality of the obtained garis was observed between operators (lightness, swelling capacity, starch content, texture and colour). These results suggest that technological improvements to the gari process could be achieved by appropriate management of the roasting and dewatering parameters., Role of process parameters in gari quality during handmade roasting of mashes with different water content.

Advancements in the field of residuals, sludge, and biosolids have been made in 2019. This review outlines the major contributions of researchers that have been published in peer-reviewed journals and conference proceedings throughout 2019 and includes brief summaries from over 125 articles. The review is organized in sections including life cycle and risk assessments; characteristics, quality, and measurement including micropollutants, nanoparticles, pathogens, and metals; sludge treatment technologies including dewatering, digestion, composting, and wetlands; disposal and reuse including adsorbents, land application and agricultural uses, nutrient recovery, and innovative uses; odor and air emissions; and energy issues.

Cellulose filter aid (CFA), a skeleton builder, has been studied for sludge conditioning at laboratory scale because of its function in reducing compressibility of sludge cake. However, there are few practical applications of CFA at the pilot and factory scales. In this study, we combined CFA with an advanced sludge dewatering technology, in practical applications. For jar test, the optimum CFA dose was 3 wt.% dry solid (DS); furthermore, the combination of CFA with polyaluminum chloride (PAC) and polyacrylamide (PAM) resulted in the lowest moisture content (73.92%) and the highest calorific value (13,628 kJ/kg) of the sludge cake. In the pilot test, the 5 wt.% DS of the CFA resulted in the optimal sludge feeding amount. In the factory test, the optimal CFA dose was further increased to 10%, and the amount of sludge feeding in a single batch was 20.5% higher than that without CFA. The optimal dose of CFA in the jar-pilot-factory test increased, which may occur because the CFA more easily penetrated the cake and performed better in building the skeleton when the sludge cake was thin. This study could provide a reference for the application of CFA and other skeleton builders in sludge dewatering and drying. PRACTITIONER POINTS: An advanced sludge treatment process-low-temperature vacuum dewatering and drying was tested. Cellulose filter aid showed good effect in jar test, pilot test, and factory test. When the scale of the experiment was from jar to factory, the optimal dosage of the cellulose filter aid was magnified. The amplification phenomenon of optimal dosage was related to the distribution pattern of cellulose filter aid in different thickness mud cakes.

BACKGROUND: The construction of small digesters will become more important for regions with demographic increase and limited areas. Savings of digester volume and a subsequently smaller footprint can be realized by the treatment of a more thickened raw sludge (high‐solid digestion). However, this operation can lead to instabilities of the anaerobic process due to rising ammonium and ammonia levels. The aim of the study was to identify the limit of saving digester volume by increasing the total suspended solids (TSS) of the treated raw sludge. RESULTS: The effects of high TSS and ammonia levels in the digested sludge were investigated in lab‐scale reactors. Ammonium nitrogen (NH₄‐N) levels were set by dosing a urea solution as well as by feeding a higher concentrated raw sludge. Chemical oxygen demand (COD) removal declined from 64 to 54% with NH₄‐N levels rising from 2000 to 3200 mg L⁻¹. However, the anaerobic biodegradation was not completely interrupted, which indicates the possible adaptation of anaerobic bacteria on high NH₄‐N levels. CONCLUSION: From the results, it can be concluded that dewatering the raw sludge up to 7% TSS leads to an optimum benefit with maximum savings in digester volume. The benefits of the operation with high solids are a lower energy demand for heating up the raw sludge and reduced construction costs (−20%) due to smaller required digester volumes. © 2019 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The effect of mono- and divalent cation concentrations on digested sludge dewatering characteristics was investigated in a full-scale study at the Harrisonburg-Rockingham Regional Sewer Authority, VA (HRRSA) and at an additional POTW (POTW B). At HRRSA, anaerobic digesters were fed with primary sludge, enhanced biological phosphorus removal (EBPR) WAS, and trucked-in DAF solids from a poultry processing facility, and digested sludge was dewatered by belt filter press. The POTW B digesters received EBPR WAS and primary sludge, and dewatering was by centrifuge. Visual MINTEQ 3.1 (Gustafsson, 2014, Visual MINTEQ 3.1. User's manual) was used to determine cation speciation and struvite, tricalcium phosphate, vivianite, and ferrous sulfide formation at a range of digestion conditions. Significant Mg and Ca complexation was predicted at all conditions evaluated, and the majority of the complexes were monovalent cations. Complexation reduced the divalent cation concentration on the order of 40%. The HRRSA and POTW B data both showed that dewatered cake total solids (TS) increased linearly with uncomplexed divalent cation concentration and that there was an increase of 1.0%-1.1% TS for every additional 1.0 meq/L of uncomplexed divalent cations. Because POTW B used centrifuge dewatering, this relationship could be independent of dewatering technique. Further, the relationship between uncomplexed divalent cation concentration and dewaterability suggests that the selectivity of exocellular polymeric substances cation exchange sites is much greater for divalent cations so that monovalent cations only bind to them when their concentrations are much higher than those of the uncomplexed divalent cations. Thus, monovalent cation concentration may not be important in anaerobic digestion or other high alkalinity environments. PRACTITIONER POINTS: It is important to account for complexation in high alkalinity environments such as anaerobic digesters; The findings of this study suggest that dewatering characteristics of anaerobically digested enhanced biological phosphorus removal (EBPR) waste sludge can be significantly improved by preserving cation-mediated exocellular polymeric substances bonding in the solids stream by reducing struvite formation; Data from two full-scale POTW's indicated that dewatered cake TS was increased by 1.0%-1.1% for every 1.0 meq/L of dissolved uncomplexed divalent cations in the anaerobic digestate bulk solution; This relationship existed for dewatering both by a belt filter press and by a centrifuge suggesting that this relationship is independent of dewatering technology; Dissolved monovalent cation concentrations may not be important in anaerobic digestion or other high alkalinity environments unless their concentrations are much greater than those of the dissolved divalent cations.

Anaerobically digested biosolids (ABD) characteristics that affect dewatering were assessed at three water resource recovery facilities (WRRF) with different handling practices. Dewatering performance at the three sites corresponded to different levels of soluble chemical oxygen demand (COD), ammonia (NH4 -N), and mono- and divalent cation concentrations in ADB. Capillary suction time (CST) and a modified centrifugal technique were used to determine optimum polymer doses and to assess the impact of handling conditions on dewatering performance. Both techniques indicated that polymer dosing between 15 and 20 kg/dry tonne was optimal for all facilities and that biosolids mixing and pumping did not significantly impact dewaterability. The CST values of anaerobically digested biosolids decreased as temperature increased, but no significant difference was found for either temperature or location of dewatering facilities. Sludge viscosity and rheological properties that vary with temperature appeared to have influenced CST values. Modified centrifugal technique results indicated cake solids were not affected by polymer make-up water or ADB temperature when emulsion polymer was used. This study shows the value of laboratory testing of biosolids under controlled conditions to identify and correct potential problems in full-scale operations. PRACTITIONER POINTS: Capillary suction time and a modified centrifugal technique were used to assess the impact of different process-related and environmental factors on dewatering. Higher concentrations of soluble COD (potentially extracellular polymeric substances - EPS) and low calcium (Ca) in anaerobically digested biosolids align with reduced dewaterability. Cell disruption and break down of floc structures due to storage/mixing and pumping of biosolids did not appear to negatively impact dewatering. Modified centrifugal test results did not provide conclusive evidence of whether dewatering of anaerobically digested biosolids could be significantly impacted by temperature over the range 15-30°C, especially when emulsion polymer is used. This study shows the value of laboratory testing of biosolids under controlled conditions to identify potential problems in the full-scale operations.

High concentration of orthophosphate ion (OP) in anaerobically digested sludge can lead to struvite crystallization, deterioration of sludge dewaterability, and elevated mainstream OP loading through centrate recirculation. The Upper Occoquan Service Authority (UOSA) has observed seasonally high OP levels in its dewatering blend tank, which was found in this study to be a consequence of unwanted biological phosphorus accumulation during the intensified winter denitrification operation and the subsequent OP release in the course of anaerobic digestion. In order to control the nuisance struvite scaling issues, a bench study was conducted and cerium chloride (CeCl3 ) was dosed as an effective OP precipitant. The results of this study demonstrated that CeCl3 dosing showed higher OP removal efficiency than other commonly used OP precipitants. In addition, bench-scale simulations indicated sludge dewaterability improvements which were used to predict lower polymer and dewatering energy demands at the full scale. The economic analysis conducted in this case study showed that the seasonal dosing of CeCl3 at UOSA has the potential to provide a net annual saving of US $47,000. PRACTITIONER POINTS: Biological phosphorus accumulation during the intensified denitrification operation caused seasonally high sludge OP and struvite scaling issues at UOSA. CeCl3 was evaluated as an effective OP precipitant for struvite control and dewaterability improvement when aluminum and iron were determined to be unfavorable. Seasonal dosing of CeCl3 at UOSA projected a net annual saving of US $47,000.

The goal of this study was to evaluate using feed dilution/solids retention time (SRT) control to manage potential ammonia inhibition in highly loaded anaerobic digesters after thermal hydrolysis. The study compared three digesters operated at the same target volatile solids (VS) loading rate of 5.5 kg VS/d-m3 , but at different feed concentrations resulting in SRTs of 10, 15, and 18 days. Lowering the feed concentration decreased the digester total ammonia nitrogen concentrations which averaged 1,580, 2,610, and 3,080 mg NH 4 + -N/L for the 10-, 15-, and 18-day digesters. The VS reduction and methane yields were equivalent for the 15- and 18-day digesters and about 4% lower for the 10-day digester. Ammonia inhibition of the 18-day digester occurred early in the study, but the system acclimated over time. Feed dilution reduced the viscosity and the potential for volume expansion due to gas holdup and foaming. PRACTIONER POINTS: Feed dilution reduces digester ammonia concentrations and inhibition potential without sacrificing digester performance at lower SRTs. Feed dilution greatly reduces digester viscosity and associated issues with digester volume expansion due to gas holdup and foaming. Operating at the lower SRT does not impact cake solids after dewatering and substantially decreases polymer demand for conditioning.

BACKGROUND: Extracellular polymeric substances (EPS) play an important role in sludge dewatering. Inorganic coagulants treatment has been widely used to remove the EPS and improve sludge dewaterability. This research evaluates whether there are advantages of selecting one of two chemical coagulation pretreatments, conventional aluminium or iron salts, over the other to enhance sludge dewaterability. The study traced variations in EPS characteristics to understand the mechanisms of sludge dewaterability. RESULTS: The results showed that iron coagulants improved dewatering more than aluminium coagulants, by approximately 28.66%. The improved sludge dewaterability was further confirmed in pilot‐scale experiments. Compared with aluminium salts conditioning, iron salts were better able to neutralize stronger charge, formed smaller and more compact flocs, and had a stronger acidification effect. Sludge dewaterability was significantly related to EPS concentrations (i.e. the protein and polysaccharides), EPS composition (i.e. tyrosine/tryptophan amino acid, tyrosine/tryptophan protein, and polysaccharide), and functional groups (i.e. random coil, β‐sheet, and Nₚᵣ) in the loosely bound EPS (LB‐EPS). A two‐step mechanism was proposed for the iron conditioning process. Moreover, the economic analysis shows iron treatment was more economical than that of aluminium. CONCLUSION: Iron salts conditioning removed more LB‐EPS than aluminium salts, thus more significantly improving sludge dewaterability. © 2018 Society of Chemical Industry

In large-scale pumping projects, such as mine dewatering, predictions are often made about the rate of groundwater level recovery after pumping has ceased. However, these predictions may be impacted by geological uncertainty-including the presence of undetected impermeable barriers. During pumping, an impermeable barrier may be undetected if it is located beyond the maximum extent of the cone of depression; yet it may still control drawdown during the recovery phase. This has implications for regional-scale modeling and monitoring of groundwater level recovery. In this article, non-dimensional solutions are developed to show the conditions under which a barrier may be undetected during pumping but still significantly impact groundwater level recovery. The magnitude of the impact from an undetected barrier will increase as the ratio of pumping rate to aquifer transmissivity increases. The results are exemplified for a hypothetical aquifer with an unknown barrier 3 km from a pumping well. The difference in drawdown between a model with and without a barrier may be

Dewatering algal suspensions is an important step in the extraction of oil and other useful substances from algae. In this study, spherical Nannochloropsis sp. and ellipsoidal Monoraphidium sp. suspensions were dewatered in the presence of different amounts of 350-nm magnetite particles using a microfiltration membrane with 360-nm pores in cross-flow mode. Magnetite functions as a filter aid by reducing the deformation of the cake of filtered algae on the membrane and providing paths for water to flow through the filtration cake of algae. In the case of Nannochloropsis sp., the highest dewatering rate was obtained when the number ratio, defined based on the size and ideal density, between Nannochloropsis sp. and magnetite was 1:12.5, but the addition of magnetite had no observable effect on the filtration of ellipsoidal Monoraphidium sp. suspensions through the membrane. After dewatering, magnetite was effectively separated from the concentrated algal suspension by the application of a magnetic field in an open flow system. Magnetite has the potential to enhance dewatering performance using a cross-flow membrane system.

There have been significant recent advances in understanding the ecohydrology of deep soil. However, the links between root development and water usage in the deep critical zone remains poorly understood. To clarify the interaction between water use and root development in deep soil, we investigated soil water and root profiles beyond maximum rooting depth in five apple orchards planted on farmland with stand ages of 8, 11, 15, 18, and 22 years in a subhumid region on the Chinese Loess Plateau. Apple trees rooted progressively deeper for water with increasing stand age and reached 23.2 ± 0.8 m for the 22‐year‐old trees. Soil water deficit in deep soil increased with tree age and was 1,530 ± 43 mm for a stand age of 22 years. Measured root deepening rate was far great than the reported pore water velocity, which demonstrated that trees are mining resident old water. The deficits are not replenished during the life‐span of the orchard, showing a one‐way mining of the critical zone water. The one‐way root water mining may have changed the fine root profile from an exponential pattern in the 8‐year‐old orchard to a relative uniform distribution in older orchards. Our findings enhance our understanding of water‐root interaction in deep soil and reveal the unintended consequences of critical zone dewatering during the lifespan of apple trees.

This paper presents a novel approach of using in‐situ microbially induced Ca2+‐alginate polymeric sealant for seepage control in porous materials. This process comprises two steps: (i) generation of insoluble calcium carbonate inside the pores of porous materials (such as sand) through a microbially induced carbonate precipitation (MICP) process in‐situ and (ii) injection of sodium alginate for in‐situ gelation via reaction between alginate and Ca2+ ions. The experimental results showed that the hydraulic conductivity/permeability of sand decreased with the increase in alginate concentration. When 5% alginate was used with a CaCO3 concentration of 0.18 g g−1 sand, the permeability of the alginate‐treated sand reduced from 5.0 × 10−4 to 2.2 × 10−9 m s−1. The scanning electron microscopy images revealed that a film‐type coating was formed around sand particles with spherical round crystals embedded. Furthermore, the in‐situ formed Ca‐alginate polymeric sealant can also be used for the removal of Cu2+ ion and suspended particles from contaminated water by more than 90%. Built on the current research, the envisioned practical application of the proposed method may include clogging fractured rock, reducing seepage and prevent piping through dams, excavation dewatering, and forming barriers for remediating specific contaminants. MOE (Min. of Education, S’pore) Published version

In view of the merits of bioleaching and surfactant for sludge treatment, the possibility of surfactant with bioleaching pretreatment applied to improve sludge dewaterability was investigated in this work. The results showed that cetyl trimethyl ammonium chloride (CTAC) with bioleaching pretreatment was highly efficient in dewatering sludge. The optimal CTAC dosage and bioleaching pH for this combination were 120 mg/g (dry solids) and 3.55, respectively, under which the water content of filtrated cake was 68.94% and the specific resistance to filtration was 0.12 × 10¹³ m/kg with a reduction of 94.92%. Although CTAC and bioleaching both had positive effects on sludge dewatering, their combination was more efficient. The significant enhancement of sludge dewaterability was mainly contributed from the breakage and charge neutralization of sludge flocs, and the release of extracellular polymeric substances (EPS). In addition, the positive correlation between supernatant EPS concentration and sludge dewaterability was observed under experimental conditions.

Ditching is a common practice to dewater wetlands, including peatlands, and ditch blocking is a common method for restoring wetlands because substrate is often unavailable for filling the ditches. However, filling has many advantages compared to blocking ditches. Our goal was to test whether ditches could be filled in a Colorado sloping fen (Chattanooga Fen) using bales created from shredded aspen (Populus tremuloides) tree‐fiber. We monitored water table levels before and after we filled two ditches (combined length of approximately 165 m × 3 m wide) as well as an undisturbed reference portion of Chattanooga fen. The reference site had stable water tables that rarely dropped more than 20 cm below the soil surface. The ditches had been dewatering large areas of the fen for at least 100 years. Filling the ditches with fiber bales resulted in a water table increase between 2 and 22 cm in an area up to 150 m below the ditch. Native sedges now cover the area where we filled the ditches, with no erosion or compression/settling of the ground observed and no water backing up behind the filled ditches. Filling the ditches with shredded fiber bales is a good option for restoration in wilderness areas, or areas lacking peat or mineral soil fill because it is a natural material that is easily transported and placed in the ditches.

A comprehensive computational fluid dynamics simulation was developed to rational design of bioethanol purification system via pervaporation process by tailoring hydrodynamics of the process. The process involves removal of water from a water/ethanol liquid mixture using a dense polymeric membrane. The model domain was divided into two compartments including feed and membrane. For description of water transport in the feed solution, Maxwell-Stefan approach was used, while for mass transfer inside the membrane the molecular diffusion mechanism was assumed. The governing equations were solved numerically using finite element method. The model was capable of predicting mass transfer along with momentum transfer in the feed and membrane compartments. The results also confirmed that formation of concentration layer can be easily predicted using Maxwell-Stefan approach in dewatering of organic compounds using pervaporation process.

A method was proposed for determining the compression-permeability data expressed as the dependences of the local specific cake resistance and local cake porosity on the solid compressive pressure from a combined membrane filtration and stepped cake compression test. Filtration employing a membrane with a high flow resistance which provided the pressure dependence of the average specific cake resistance was followed by step-up compression which gave cake porosities at several compressive pressures. On the basis of these data collected as the time variation of the dewatering volume, the compression-permeability data of bentonite slurry were evaluated. Consolidation behaviors of the filter cake and semi-solid material were accurately described based on the compression-permeability data.

Industrial scroll decanter centrifuge (SDC) separation of the solids in fluid fine tailings (FFT) which have particles 10 μm and smaller in size require flocculant addition. Accordingly, the mechanism in the centrifuge is flocculation of the fine solid particles followed by sedimentation. Thus, feeding preflocculated material obviates the flocculation step inside the SDC resulting in improved process efficiency by reducing the power consumption and increasing the throughput capacity of each SDC. This work evaluated the separation performance of the SDC using inline static mixers to preflocculate oil sands FFT containing solids, 90 mass% of which are 97 % fines capture rate were 750 G without preflocculation and 400 G with preflocculation. Since power consumption by the SDC, as expected, was directly proportional to the G-force, the savings in power due to preflocculation amounted to 47 %. Preflocculation increased SDC throughput capacity by up to 50 %. Operating at lower G-force has the additional benefits of protecting the high-capital-cost SDC machine and reducing ambient noise levels.

In the baking industry, fresh yeast is generally available as a compressed paste containing about 70% moisture. While much literature has been published on its growth conditions in fermentation tanks, little information may be obtained on the final steps of baker's yeast production. In this review, 226 patents were found on the separation of yeast cells from spent growth media as well as its dewatering, forming, and packaging in the compressed form. The latter corresponded to 21% of 1096 unique families of patented inventions filed worldwide between 1787 and 2014 on the production of fresh baker's yeast. Patent specifications disclosed key technical information not available in scientific journals. Particularly between 1890 and 1960, highly specific equipment such as centrifugal separators, rotary vacuum filters, and extruding and cutting units were proposed. Compressed yeast may contain small amounts of processing aids, including water-absorbing agents such as starch and salt, as well as plasticizing and whitening agents. Any variation in yeast solids and moisture contents will affect its gassing power and keeping properties. Disposal and proper treatment of very large volumes of spent growth media will remain a major challenge to the baker's yeast industry.