Tolga Tunçal

A Review of Dehydration of Various Industrial Sludges

Wastewater characteristics and sludge generation potential of point source categories are reviewed critically. Novel industry-specific sludge dewatering/drying solutions necessary to establish a sustainable model are examined through a detailed literature survey. Knowledge of sludge properties is one of the most critical issues needed to design dewatering/drying equipment. This study focuses on industrial wastewater/sludge characterization. In addition, a comprehensive review of current drying models and technologies is also presented. A summary of the results derived from a novel thin-film-based photonic sludge dewatering/drying study is outlined as an alternative approach for industrial sludge control. Sludge was dried in a tubular quartz reactor (TQR), the inner surface of which was coated with a TiO2 thin film. The TQR was irradiated with UV A, UV B, and UV C lamps. The consumed and generated energy fluxes through endergonic and exergonic reactions driven by photolysis and photocatalysis were investigated. In addition, the variations in sludge dewatering/drying characteristics were also examined and compared with conventional methods to evaluate the energy requirements.

Abatement of Organic Pollutant Concentrations in Residual Treatment Sludges: A Review of Selected Treatment Technologies Including Drying

As a result of increasing population, industrialization, and effluent quality, sludge production has increased worldwide. Organic micropollutants in sludge have become a more critical environmental health concern compared to heavy metals. New sludge disposal regulations limit persistent organic pollutants (POPs) in addition to conventional organic indicators like total and dissolved organic carbon. This study aims at providing a brief review on POP concentration in the sludge in different regions of the world, sludge regulations, assessment of conventional biological sludge stabilization methods according to their ability to remove POPs, and discussions on alternative sludge treatment methods. The impact of sludge treatment unit operations including conditioning, thickening, mechanical and thermal dewatering, and biological and thermal stabilization on sludge management is also discussed in the context of organics. The occurrence and removal of micropollutants such as absorbable organic halogen compounds (AOX), nonylphenol and nonylphenol ethoxylates (NPE), di-2-(ethyl-hexyl)-phthalate (DEHP), dibenzo-p-dioxins and furans (PCDD/F), polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) are also evaluated specifically for sludge treatment unit operations. A concise discussion is also included on different drying technologies suitable for drying of sludge.

Evaluating Drying Potential of Different Sludge Types: Effect of Sludge Organic Content and Commonly Used Chemical Additives

Drying of residual treatment sludge is one of prerequisites in final disposal of this hazardous material. In this study, sludge drying potential (SDP) of different sludge types (DST) and the effect of organic content and commonly used chemical additives, including polyelectrolyte and lime, on SDP were investigated in a full-scale municipal wastewater treatment plant (WWTP). Freshly collected sludge samples were used in all experiments, which were conducted in onsite laboratory of sludge treatment facility. Studied sludge types were composed of raw biological sludge (RBS), raw primary sludge (RPS), mixed sludge (MS), dewatered sludge (DS), and limed sludge (LS). Halogen radiation was used for sludge drying. Organic content of sludge was represented by total organic carbon (TOC), dissolved organic carbon (DOC), and lost on ignition (LOI) parameters. Relations and interactions among the SDR(s) of DST(s) were statistically determined using independent samples t-test. The effect of organic content and chemicals additives on SDP was also statistically analyzed using linear regression model. Results of the study imply that each surveyed sludge type had a different SDP. Furthermore, organic composition of sludge and chemical additives had a significant impact on SDP.

Comparing alkaline and thermal disintegration characteristics for mechanically dewatered sludge.

Thermal drying is one of the advanced technologies ultimately providing an alternative method of sludge disposal. In this study, the drying kinetics of mechanically dewatered sludge (MDS) after alkaline and thermal disintegration have been studied. In addition, the effect of total organic carbon (TOC) on specific resistance to filtration and sludge bound water content were also investigated on freshly collected sludge samples. The combined effect of pH and TOC on the thermal sludge drying rate for MDS was modelled using the two‐factorial experimental design method. Statistical assessment of the obtained results proposed that sludge drying potential has increased exponentially for both increasing temperature and lime dosage. Execution of curve fitting algorithms also implied that drying profiles for raw and alkaline‐disintegrated sludge were well fitted to the Henderson and Pabis model. The activation energy of MDS decreased from 28.716 to 11.390 kJ mol−1 after disintegration. Consequently, the unit power requirement for thermal drying decreased remarkably from 706 to 281 W g−1 H2O.

Industrial sludge remediation with photonic treatment using Ti–Ag nano-composite thin films: Persistent organic pollutant removal from sludge matrix

Mechanically dewatered industrial sludge (MDIS) was treated using pure and silver-doped thin films (TFs) grown on quartz substrates. TFs were prepared using a sol-gel dip coating technique. The resulting films were annealed at 450 °C for 3 h and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Mixtures that were homogeneous in the UV A (380 nm) and UVvis (450 nm) regions of the electromagnetic spectrum were used as the irradiation source. The results revealed that illumination with different wavelengths helps to generate well-separated e(-)/h(+) pairs, resulting in a decrease in the recombination rate. An electron transfer chain model was also developed using the experimental results. The performance of the applied method was evaluated by observing variations in the sludge bound water content (SBWC), volatile solids removal rate (VSR), and the consumed and generated energy fluxes through endergonic and exergonic reactions. After treatment, SBWC was reduced from 65% ± 1% to 39% ± 1 and the highest VSR was measured to be 27 ± 0.1 mg VSS cm(-2) h(-1). The consumed and recovered energy fluxes were 960 ± 151 and 412 ± 26 J g(-1) VS(removed), respectively. Raw sludge and polychlorinated biphenyls (∑(15)PCB) and polyaromatic hydrocarbon (∑(16)PAH) concentrations were 4356.82 ± 22 μg kg(-1) and 446.25 ± 4.8 μg kg(-1), respectively. The ∑(15)PCB and ∑(16)PAH concentrations in the treated sludge samples were 129.86 ± 22 μg kg(-1) and 34.85 ± 1.3 μg kg(-1), respectively.

Importance of particulate biodegradable organic compounds in performance of full-scale biological phosphorus removal system.

In this study, biological treatment performances of two parallel treatment lines operating with and without primary sedimentation were investigated. The research was carried out in a large-scale enhanced biological phosphorus removal (EBPR) process. Influent and effluent of treatment lines were characterized continuously during the study. In addition, anaerobic anoxic and aerobic EBPR activities were investigated by batch tests using fresh activated sludge samples. All of the environmental and operational conditions of the treatment lines were statistically compared. Evaluation of effluent compositions indicated that EBPR performances of treatment lines were significantly different. Results of the research also indicated that settling characteristics of the activated sludge process could be improved significantly with increasing particulate biodegradable organic compound (pbCOD) loading rate. Batch test results revealed that anaerobic, anoxic, and aerobic biochemical reaction rates of activated sludge cultivated on increased pbCOD loading rate were significantly higher compared to activated sludge cultivated on soluble substrate forms.

Model-based evaluation of microbial mass fractions: effect of absolute anaerobic reaction time on microbial mass fractions.

Although enhanced biological phosphorus removal processes (EBPR) are popular methods for nutrient control, unstable treatment performances of full‐scale systems are still not well understood. In this study, the interaction between electron acceptors present at the start of the anaerobic phase of an EBPR system and the amount of organic acids generated from simple substrate (rbsCOD) was investigated in a full‐scale wastewater treatment plant. Quantification of microbial groups including phosphorus‐accumulating microorganisms (PAOs), denitrifying PAOs (DPAOs), glycogen‐accumulating microorganisms (GAOs) and ordinary heterotrophic microorganisms (OHOs) was based on a modified dynamic model. The intracellular phosphorus content of PAOs was also determined by the execution of mass balances for the biological stages of the plant. The EBPR activities observed in the plant and in batch tests (under idealized conditions) were compared with each other statistically as well. Modelling efforts indicated that the use of absolute anaerobic reaction (ηı) instead of nominal anaerobic reaction time (η), to estimate the amount of available substrate for PAOs, significantly improved model accuracy. Another interesting result of the study was the differences in EBPR characteristics observed in idealized and real conditions.