Drinking Water Treatment Plant Sludge Research Articles

Hierarchical Approach to the Management of Drinking Water Sludge Generated from Alum-Based Treatment Processes

The management of drinking water treatment plant (DWTP) sludge is challenging for water treatment facilities. Previous studies reported mainly on handling sludge through landfilling, release into water bodies, discharge into wastewater treatment plants, onsite disposal, and incineration methods for the treatment of sludge. The limitations of these sludge-handling methods are well documented. This article focuses on the hierarchical approach as an alternative and comprehensive method for handling DWTP sludge. The core of hierarchical management streamlines the minimization of the generated DWTP sludge; treatment of DWTP sludge to reduce toxicity; changing of the physicochemical form of DWTP sludge; and finally, the reuse, recycling, and recovery of DWTP sludge. The premise is to achieve zero landfilling of DWTP sludge, establish a circular economy, generate job opportunities, and preserve the environment. Thus, this study also proposes two main technologies, which are gravity-based sludge separators for fractionating the sludge and photocatalytic membrane reactors (PMRs) as a technology for the treating and/or recovery of nutrients and minerals from DWTP sludge. Until the chemical deductive or minus approach becomes a reality in water treatment, the use of PMRs and gravity-based sludge separators will enhance the management of DWTP sludge when incorporated into the hierarchical approach.

Dewatering performance of aerobic granular sludge under centrifugal with different sludge conditioning agent.

The aerobic granular sludge(AGS) technology draw scientific researchers attention, and more and more scientific research focuses on it, due to its superior advantages, such as good settling performance, high biological phase, high toxicity resistance and multiple biological effects. With the rapid development of AGS technology, a considerable amount of residual AGS will be produced, and dehydration is the biggest bottleneck of sludge reduction. This study investigated the dewatering process and method of residual AGS cultured by continuous flow experiment. Experiments were conducted using centrifugal dewatering technology with a dosing scheme to analyze the granular sludge dewatering process, and investigate the release process of EPS component in AGS dewatering. Our results implied the specific resistance of AGS has a very low value ((1.82 ± 0.03) × 109 m/kg) and it was not obvious for the conditioning effect of chemical conditioner on AGS dewatering. However, the moisture content can be reduced to 63.5% after dewatering with the presence of inorganic substances. The addition of drinking water treatment plant sludge (Alum sludge) can improve the efficiency of the dewatering of AGS. A possible dewatering process of AGS dewatering was proposed which was divided into two stages: First, a considerable amount of free water in the sludge was quickly removed under the action of gravity without pressure filtration. Second, the bound water release required cooperation between applying centrifugal or pressing force to grind granular cells and separate protein-like substances with the inorganic matter inside the granular sludge. The possible mechanism of AGS dewatering and hypothesis dewatering process are useful to optimize the AGS dewatering process.

Impact of Stagnation on the Diversity of Cyanobacteria in Drinking Water Treatment Plant Sludge.

Health-related concerns about cyanobacteria-laden sludge of drinking water treatment plants (DWTPs) have been raised in the past few years. Microscopic taxonomy, shotgun metagenomic sequencing, and microcystin (MC) measurement were applied to study the fate of cyanobacteria and cyanotoxins after controlled sludge storage (stagnation) in the dark in a full-scale drinking water treatment plant within 7 to 38 days. For four out of eight dates, cyanobacterial cell growth was observed by total taxonomic cell counts during sludge stagnation. The highest observed cell growth was 96% after 16 days of stagnation. Cell growth was dominated by potential MC producers such as Microcystis, Aphanocapsa, Chroococcus, and Dolichospermum. Shotgun metagenomic sequencing unveiled that stagnation stress shifts the cyanobacterial communities from the stress-sensitive Nostocales (e.g., Dolichospermum) order towards less compromised orders and potential MC producers such as Chroococcales (e.g., Microcystis) and Synechococcales (e.g., Synechococcus). The relative increase of cyanotoxin producers presents a health challenge when the supernatant of the stored sludge is recycled to the head of the DWTP or discharged into the source. These findings emphasize the importance of a strategy to manage cyanobacteria-laden sludge and suggest practical approaches should be adopted to control health/environmental impacts of cyanobacteria and cyanotoxins in sludge.

Experimental investigation of the feasibility of using drinking water treatment plant sludge in the improvement of sandy soils

Experimental investigation of the feasibility of using drinking water treatment plant sludge in the improvement of sandy soils

A circular economy use of waste drinking water treatment plant sludge for magnetic photocatalyst composite production into wastewater treatment

ABSTRACT Environmental remedy calls for scientific contributions with ever increasing urgency. This research aims to a circular economy look to deliver the concept of novel materials, created from renewable by-product waste feedstock and designed to be reused, recycled, then the feedstock renewed through wastewater treatment process. The use of alum sludge (AS) waste as a photocatalyst in the catalytic oxidation of wastewater to the potential capability of ˙OH radical use as a strong oxidant is explored. Investigation has performed using magnetite (M) augmented with alum sludge as a composite material formed as alum sludge/magnetite (ASM) at different proportions (1:1), (1:2), (1:3), (1:5) and (2:1) and the samples labelled as ASM-1, ASM-2, ASM-3, ASM-4 and ASM-5, respectively. The characterisation of such composite materials was explored by X-ray diffraction (XRD), Transmission electron Microscopy (TEM) and the composition of the composite material is attained by the Energy dispersive X-ray spectroscopy (EDX). The capabilities of these materials are tested for dye removal. Consequently, the corresponding photocatalytic performance was notably improved. The various operating conditions, initial dye concentration, initial pH value, catalyst and H2O2 concentrations on the oxidation efficiency of the dye were optimised at pH 2.0 and 800 mg/L and 2 g/L for H2O2 and ASM-1, respectively. Thermodynamic and kinetics were studies and the data revealed that the reaction is spontaneous and exothermic in nature and follows the first-order reaction kinetics. This assessment introduces the role of engineers and chemists in a world without waste.

An Experimental Investigation of Reinforcement Thickness of Improved Clay Soil with Drinking Water Treatment Sludge as an Additive

The aim of this research was to investigate the use of drinking water treatment plant sludge (DWTS) industrial waste by-products, as alternative environmental additives in soil improvement projects. For this reason, in the first stage, the optimum mixing ratio of DWTS was determined. In the second stage, different H/D ratios were evaluated in the investigation of appropriate reinforcing thicknesses in the improvement of clay soil + DWTS mixtures. A geogrid was placed between the two soil layers for separation in this stage. In the third stage, consolidation settlements were investigated before and after improvement with DWTS. In the last stage, the reinforcement mechanism of clay soil + DWTS mixtures were investigated using scanning electron microscopy. As a result, the optimum mixing ratio of DWTS was found to be 10%. The bearing capacity of clay soil increased 1.69 times using DWTS. The optimum reinforcement thickness was determined as H/D = 2.25. We found that consolidation settlements decreased by up to 62%. Thus, the experimental results showed that the use of DWTS as an additive for soil improvement was an economical and environmentally friendly approach.

Synthesis and characterisation of Portland cement clinker by exploiting waste oyster shells and alumina sludge

Significant quantities of oceanic waste oyster shells and drinking water treatment plant sludge (alumina sludge) raise serious issues on eco-toxicology and environmental protection. In order to manipulate these issues, the present research work investigates the valorisation capability of the mentioned waste materials as raw meal substitutes for Portland clinker production. The clinkers and their respective cements thus obtained have been structurally characterised by various structural analysis techniques including, X-ray fluorescence, scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. Structural analysis results reveal that the replacement of clinker raw materials by waste oyster shells and alumina sludge positively influences the morphology of the formed clinker/cement. In addition, the development of compressive strength of this waste-based cement has been found similar to that of standard Portland cement (type 52.5N) which justifies its commercialisation potential. A detailed account of the interpretations of invaluable physico-chemical parameters regarding the clinker/cement along with the prospective applications of the present study is also discussed.

Development of a floating adsorbent for cadmium derived from modified drinking water treatment plant sludge

Abstract Adsorbents produced from solid waste materials have received a lot of attention in recent years. The purpose of this study was to assess the aqueous phase cadmium adsorption capacity of a floating adsorbent derived from a drinking water treatment sludge. Unmodified sludge, phosphoric acid modified sludge powder, and granular encapsulated sludges were investigated. Parameters such as adsorbent concentration, contact time, pH of the solution, and the initial concentration of cadmium ions were investigated using batch sorption experiments. SEM, FTIR, and elemental analysis techniques were utilized for the characterization of the adsorbent. The Langmuir model was employed to determine the adsorption capacity of all four adsorbents. The maximum cadmium load increased from 25 mg/g for the unmodified sludge to 40.3 mg/g for the phosphoric acid modified material. The alginate gel-encapsulated sludge adsorbed 30 mg/g, slightly higher than that of the raw sludge. The granular form of the encapsulated material made it easier to remove the adsorbent from the aqueous phase after the adsorption process. The findings of this research have important implications for the removal of aqueous phase cadmium using sludge based, low-cost adsorbents.

Adsorption of Carbon Dioxide by Reusing Drinking Water Treatment Plant Sludge

Cost effective, easy to use and regenerate could be the desired properties of an adsorbent. Reusing of waste material as CO2 adsorbent can be a good alternative for solving the problem of waste disposal as well. Thus, in this study, aluminium-based drinking water treatment plant sludge as carbon dioxide adsorbent was reused. The sludge collected from a local drinking water treatment plant. It was dried and characterized using scanning electron microscope-energy disperse X-ray (SEM-EDX), Fourier transform infrared spectrometer (FTIR) and thermogravimetric analysis (TGA). Investigations of the effects of temperature, flow rate, concentration of CO2 and adsorbent dosage on CO2 adsorption capacity were performed using a fixed bed column at a pressure of 1 bar. The maximum capacity of 32.56 mg/g was found which was higher than that of some reported adsorbents.

Determination of key components and adsorption capacity of a low cost adsorbent based on sludge of drinking water treatment plant to adsorb cadmium ion in water

A low cost adsorbent based on sludge of drinking water treatment plant (DWTP), solid waste by-product of sedimentation process in the DWTP, was studied for adsorption of cadmium ion in water. Some parameters such as dose of the adsorbent, pH of solution, and shaking time were investigated in the batch system in order to know the optimum condition and adsorption ability of the adsorbent. Artificial sludge was prepared by following the process of DWTP and the effect of humic acid extracted from the DWTP sludge was examined in order to clarify the key component and adsorption capacity of the adsorbent. This study found that humic acid and iron oxide were the key components of the adsorbent material for adsorption of cadmium ion in water. The Langmuir isotherm adsorption model was fit and the adsorption capacity of the adsorbent based on sludge of Miyamchi and Nishino DWTP for Cd(II) was 5.3 and 9.2mg/g, respectively. The finding of this study is important for further development of a low cost adsorbent material in the near future.

High Efficiency Aluminum Coagulant Recovery from Drinking Water Treatment Plant Sludge by Using Ultrasound Assisted Acidification

In this study, a novel combination of ultrasound with acid for coagulant recovery from drinking water treatment plant sludge (DWTPS) is investigated in view of improving the coagulant recovery efficiencies. Optimal recovery conditions, a sulfuric acid concentration of 2.0 M, an ultrasonic treatment time of 30 minutes, an ultrasound power of 1000 W and stirring speed of 1000 rpm, have been found in the lab test. The aluminum recovery rates from acidification process with assistance of ultrasound increased by approximately 20% compared with that of acidification only. It was found that the synergistic effects between acid with ultrasound contribute to improving the treatment efficiency.

Characterization of eco-cement paste produced from waste sludges

In this study, marble sludge, sewage sludge, drinking water treatment plant sludge, and basic oxygen furnace sludge were used as replacements for limestone, sand, clay, and iron slag, respectively, as the raw materials for the production of cement in order to produce eco-cement. It was found that it is feasible to use marble sludge to replace up to 50% of the limestone and also that other materials can serve as total replacements for the raw materials typically used in the production of cement. The major components of Portland cement were all found in eco-cement clinkers. The eco-cement was confirmed to produce calcium hydroxide and calcium silicate hydrates during the hydration process, increasing densification with the curing age. The compressive strength ( S c ) and microstructural evaluations conducted at 28 d revealed the usefulness of eco-cement. It was observed that the S c data correlated linearly with the pore volume ( P) data at 28 d. The proposed model equation could be represented as S c = 178–461P (correlation coefficient, R 2 = 0.96). Two parameters, the large capillary pore volume and the medium capillary pore volume, were evaluated using multiple regression analysis.

Re-use of drinking water treatment plant (DWTP) sludge: Characterization and technological behaviour of cement mortars with atomized sludge additions

This paper aims to characterize spray-dried DWTP sludge and evaluate its possible use as an addition for the cement industry. It describes the physical, chemical and micro-structural characterization of the sludge as well as the effect of its addition to Portland cements on the hydration, water demand, setting and mechanical strength of standardized mortars. Spray drying DWTP sludge generates a readily handled powdery material whose particle size is similar to those of Portland cement. The atomized sludge contains 12–14% organic matter (mainly fatty acids), while its main mineral constituents are muscovite, quartz, calcite, dolomite and seraphinite (or clinoclor). Its amorphous material content is 35%. The mortars were made with type CEM I Portland cement mixed with 10 to 30% atomized sludge exhibited lower mechanical strength than the control cement and a decline in slump. Setting was also altered in the blended cements with respect to the control.

Toxicity of ferric chloride sludge to aquatic organisms

Iron-rich sludge from a drinking water treatment plant (DWTP) was investigated regarding its toxicity to aquatic organisms and physical and chemical composition. In addition, the water quality of the receiving stream near the DWTP was evaluated. Experiments were carried out in August 1998, February 1999 and May 1999. Acute toxicity tests were carried out on a cladoceran (Daphnia similis), a midge (Chironomus xanthus) and a fish (Hyphessobrycon eques). Chronic tests were conducted only on D. similis. Acute sludge toxicity was not detected using any of the aquatic organisms, but chronic effects were observed upon the fecundity of D. similis. Although there were relatively few sample dates, the results suggested that the DWTP sludge had a negative effect on the receiving body as here was increased suspended matter, turbidity, conductivity, chemical oxygen demand (COD) and hardness in the water downstream of the DWTP effluent discharge. The ferric chloride sludge also exhibited high heavy metal concentrations revealing a further potential for pollution and harmful chronic effects on the aquatic biota when the sludge is disposed of without previous treatment.

Biosorption of cadmium by various types of dried sludge: An equilibrium study and investigation of mechanisms

Batch equilibrium sorption experiments were used for screening for cost-effective four types of sludge, which were DWS (drinking water treatment plant sludge), LLS (landfill leachate sludge), ADSS (anaerobically digested sewage sludge), and SS (sewage sludge). SS removed cadmium most efficiently from aqueous solution (0.38 mmol/g), and showed the highest desorption efficiency (26.3%). Only the SS can be fitted by Langmuir isotherm model ( r 2 = 0.996). The FT-IR spectra of SS and cadmium loaded SS indicated that carboxyl groups were major binding sites of cadmium binding sites. In kinetic experiment, it was found that the uptake of the metal by the SS was accompanied with proton release, indicating that the metal binding occurs via an ion exchange as well as by electrostatic interaction between carboxylate groups and cadmium ions. This sorbent may have a potential for use as high-value biosorbent of heavy metals and it deserves further investigations into the details of practical application, for example on the development of desorption methods and on sorption process optimization.

The contribution of azo dyes to the mutagenic activity of the Cristais River

To verify whether dyes emitted within the discharge of a dye processing plant were contributing to the mutagenicity repeatedly found in the Cristais River, São Paulo, Brazil, we chemically characterized the following mutagenic samples: the treated industrial effluent, raw and treated water, and the sludge produced by a Drinking Water Treatment Plant (DWTP) located ∼6 km from the industrial discharge. Considering that 20% of the dyes used for coloring activities might be lost to wastewaters and knowing that several dyes have mutagenic activity, we decided to analyze the samples for the presence of dyes. Thin layer chromatographic analysis indicated the presence of three prevalent dyes in all samples, except for the drinking water. This combination of dyes corresponded to a commercial product used by the industry, and it tested positive in the Salmonella assay. The structures of the dye components were determined using proton magnetic resonance and mass spectrometric (MS) methods, and the dyes were tested for mutagenicity. The blue component was identified as the C.I. Disperse Blue 373, the violet as C.I. Disperse Violet 93, and the orange as C.I. Disperse Orange 37. The dyes showed mutagenic responses of 6300, 4600, and 280 revertants/μg for YG1041 with S9 respectively. A bioassay-directed fractionation/chemical analysis showed that the C.I. Disperse Blue 373 contributed 55% of the mutagenic activity of the DWTP sludge. We showed that these dyes contributed to the mutagenic activity found in the Cristais River environmental samples analyzed and are indirectly affecting the quality of the related drinking water. Therefore, we believe that this type of discharge should be more thoroughly characterized chemically and toxicologically. Additionally, human and ecological risks associated with the release of dye processing plant effluents should be more fully investigated, especially where the resultant water is taken for human consumption.