Fate and effect of Polyamide-6 microplastics in mesophilic and thermophilic anaerobic digestion.

Research has demonstrated that depending on the type and concentration, microplastics affect anaerobic digestion (AD). Owing to the high abundance of polyamide-6 (PA6) in wastewater treatment plants and limited understanding of its behavior, this study investigates PA6 microplastics' effect in AD. Biochemical methane potential experiments were performed under mesophilic (35 °C) and thermophilic (55 °C) conditions using PA6 at concentrations from 0 to 200 particles/g total solids (TS).

Microplastics and organics - A comparative study of sorption of triclosan and malachite green onto polyethylene.

This study aims to elucidate interaction of organics with microplastics in a comparative manner via the use of two model compounds (i.e., triclosan (TCS) and malachite green (MG)) having different physicochemical properties, onto polyethylene (PE).

Fate and effects of polyethylene terephthalate (PET) microplastics during anaerobic digestion of alkaline-thermal pretreated sludge.

Plastics are resilient, hard to degrade materials that can persist in nature for centuries. Microplastics (MPs) exhibit similar tough character and hold the potential to harm marine and terrestrial ecosystems upon their release into the environment. Most modern wastewater treatment plants remove MPs from wastewater with over 90% efficiency but unfortunately concentrate them in sludge.

Comprehensive analysis and modeling of landfill leachate.

Landfill leachate data compiled from 220 different landfills from 46 countries in Europe, Middle East, Asia, Africa, and America was analysed by multivariate statistical approaches. Data pre-treatment procedure such as handling of outliers, completion of missing data, and standardization of data was applied to prepare the raw data matrix for the complex statistical analyses including cluster and principal component analyses (PCA). Regression modeling was conducted to estimate leachate parameter values.

Sewage sludge as a source of microplastics in the environment: A review of occurrence and fate during sludge treatment.

Modern wastewater treatment plants (WWTPs) effectively remove microplastics (MPs) from wastewater and unsurprisingly concentrate them in sludge. Hence through its beneficial use and disposal, sludge causes secondary release pathways of an estimated average amount of 10 to 10 wastewater-based MPs to various environmental compartments yearly. Despite these numbers, studies investigating sludge are scarce.

Effects of anaerobic digestion enhanced by ultrasound pretreatment on the fuel properties of municipal sludge.

In this study, effects of ultrasound pretreatment on combustion characteristics and elemental composition of municipal sludge were examined for energy-based evaluation of sludge pretreatment. Waste activated sludge (WAS) from a municipal wastewater treatment plant was pretreated with ultrasound at varying durations and was subjected to anaerobic digestion in a biochemical methane potential (BMP) assay. Changes in gas production rates, calorific value (CV), elemental compositions, and ash contents of sludge samples were examined to assess the effects of pretreatment and digestion.

A comparative evaluation of anaerobic dechlorination of PCB-118 and Aroclor 1254 in sediment microcosms from three PCB-impacted environments.

Aroclor 1254 (A1254) is the most toxic commercial PCB mixture produced, primarily due to its relatively high concentrations of dioxin-like congeners. This study demonstrates a comparative evaluation of dechlorination of A1254 and PCB-118 by indigenous organohalide respiring bacteria enriched from three PCB impacted sites: Grasse River (GR), NY; Fox River (FR), WI; and Baltimore Harbor (BH), MD. PCB-118 dechlorination rates in GR, BH, and FR was 0.

Potential risk reduction of Aroclor 1254 by microbial dechlorination in anaerobic Grasse River sediment microcosms.

Aroclor 1254 was the second most produced commercial PCB mixture and is found in soils, sediments and sewage throughout the globe. This commercial PCB mixture is considered particularly toxic because of the relatively high concentrations of congeners with dioxin-like properties. The potential for risk reduction by microbial reductive dechlorination of Aroclor 1254 (A1254) was investigated in sediment microcosms from Grasse River (GR), Massena, NY.

Guluronic acid content as a factor affecting turbidity removal potential of alginate.

Alginates are natural polymers composed of mannuronic and guluronic acid residues. They are currently extracted from brown algae; however, alginate can also be synthesized by some species of Azotobacter and Pseudomonas. Alginates with different proportion of mannuronic and guluronic acids are known to have different characteristics and form gels at different extents in the presence of calcium ions.

Evaluation of solar sludge drying alternatives by costs and area requirements.

Thermal drying is a common method to reach above 90% dry solids content (DS) in sludge. However, thermal drying requires high amount of energy and can be expensive. A greenhouse solar dryer (GSD) can be a cost-effective substitute if the drying performance, which is typically 70% DS, can be increased by additional heat.

PCBs in sludge: development of a practical extraction procedure and its application in an urban water resource recovery facility.

Sludges originating from water resource recovery facilities act as a sink for various contaminants including polychlorinated biphenyls (PCBs). Investigation of such pollutants provides detailed information about the pollutant burden of the region from which incoming wastewater is derived. However, the current extraction methods for PCBs in wastewater and sludge are both time- and solvent-consuming.

Investigation of nonylphenol and nonylphenol ethoxylates in sewage sludge samples from a metropolitan wastewater treatment plant in Turkey.

Nonylphenol ethoxylates (NPEOs) have drawn significant attention within the last decade for both scientific and legislative reasons. In Turkey, the Regulation Regarding the Use of Domestic and Urban Sludges on Land states a limit value for the sum of nonylphenol (NP), nonylphenol monoethoxylate (NP1EO) and nonylphenol diethoxylate (NP2EO) as NPE (NPE=NP+NP1EO+NP2EO). Unfortunately a standard method for the determination of these chemicals has not been yet set by the authorities and no data exists about the concentrations of NP and NPEOs in sewage sludge in Turkey.

Fate and degradation kinetics of nonylphenol compounds in aerobic batch digesters.

Nonylphenol (NP) compounds are toxic and persistent chemicals that are not fully degraded either in natural or engineered systems. Current knowledge indicates that these compounds concentrate in sewage sludge. Therefore, investigating the degradation patterns and types of metabolites formed during sludge treatment are important for land application of sewage sludge.

Toxicity of nonylphenol diethoxylate in lab-scale anaerobic digesters.

Nonylphenol compounds have high commercial, industrial and domestic uses owing to their surface active properties. In addition to their toxic, carcinogenic and persistent characteristics; they have drawn the attention of scientists lately due to their endocrine disrupting properties. Their widespread use and disposal cause them to enter wastewater treatment systems at high concentrations.

Impact of PCB-118 and transformer oil toxicity on anaerobic digestion of sludge: anaerobic toxicity assay results.

In this study, possible toxicity of increasing doses of PCB-118 and transformer oil (TO) on anaerobic sludge digestion was investigated. For this purpose, five different sets of reactors were prepared in which four different PCB-118 concentration (1, 10, 20, and 30mgL(-1)) and three different TO concentration (0.38, 0.

Effect of digester F/M ratio on gas production and sludge minimization of ultrasonically treated sludge.

Sludge pretreatment by mechanical, chemical or thermal methods before anaerobic digestion has been applied to increase the digestability of excess sludge. Pretreatment processes rely on their ability to disrupt cell membranes and to release organic materials from the cells into the aqueous phase. Pretreatment by mechanical disintegration has grown rapidly in recent years in parallel with the advances in technology.

Ultrasonic pretreatment and subsequent anaerobic digestion under different operational conditions.

In this study ultrasonic pretreatment was investigated in order to improve anaerobic digestion. First, the most effective sonication time was selected during the preliminary studies conducted on waste activated sludge samples. Then the optimal time selected was confirmed running batch anaerobic reactors.

Alkaline solubilization and microwave irradiation as a combined sludge disintegration and minimization method.

Commonly used pretreatment method of alkaline solubilization (using NaOH) and a relatively new technology of microwave (MW) irradiation (160 degrees C) were combined as a pretreatment method of waste activated sludge (WAS) in this study. First alkaline and MW pretreatment methods were examined separately, then their combination for different conditions was investigated in terms of their effect on COD solubilization, turbidity and capillary suction time (CST). For combined pretreatments, soluble COD to total COD ratio (SCOD/TCOD) of WAS increased from 0.

Phosphorus defficiency and sludge bulking.

Separation by settling is one of the most troublesome stages of an activated sludge process. A decrease in the efficiency of separation of microbial biomass from the treated effluent causes a decrease in the overall efficiency of the treatment plant. One of the most common problems in activated sludge systems to negatively influence the settleability is sludge bulking which can be defined as non-settling situation of microbial mass.

An investigation of heavy metal biosorption in relation to C/N ratio of activated sludge.

The effect of C/N ratio of activated sludge on heavy metal biosorption was investigated. Three sets of semi-continuous reactors with different feed C/N ratios (9, 21 and 43 mg COD/mg TKN) were set up. Sorption equilibrium tests have indicated that the biosorptive capacity of activated sludge was highly dependent on metal species and the C/N ratio.

Enzymatic extraction of activated sludge extracellular polymers and implications on bioflocculation.

This study examines enzyme hydrolysis, a mild, effective, but a rarely used method of extracellular polymer extraction, in removing polymers from mixed culture activated sludge flocs. Two carbohydrate specific enzymes (alpha-amylase and cellulase) and a protein specific enzyme (proteinase) are used during the study. First, the kinetic aspect is investigated, then enzyme dose optimization is carried out on laboratory grown activated sludge samples cultured at solids retention times (SRT) of 4 and 20 days.

Use of Fenton oxidation to improve the biodegradability of a pharmaceutical wastewater.

The applicability of Fenton's oxidation to improve the biodegradability of a pharmaceutical wastewater to be treated biologically was investigated. The wastewater was originated from a factory producing a variety of pharmaceutical chemicals. Treatability studies were conducted under laboratory conditions with all chemicals (having COD varying from 900 to 7000 mg/L) produced in the factory in order to determine the operational conditions to utilize in the full-scale treatment plant.

A study of the dental solid waste produced in a school of dentistry in Turkey.

Dental wastes are regulated under medical waste control regulations in most countries. Even though the quantity of hazardous wastes in dental solid wastes is a small proportion, there is still cross infection risk and potential danger for environment associated with mismanaged wastes. For this reason, knowledge of waste composition and development of proper management alternatives are necessary.