Primary Sedimentation Research Articles

Secondary dolomitization of the Domanik black shales as an indicator of gas-water hydrocarbon-containing fluids upward migration in the Tatarstan territory

The share of unconventional oil reserves is high in Russia and Volga-Ural region, including shale oil reservoirs. It contains around 65% of the total volume of hydrocarbon reserves in region, according to various data. Shale hydrocarbons are widely used in Russia. The main part of the Domaniki oil black shale is confined to carbonate-siliceous carbonaceous complexes of the Domanik horizon of the Francian stage of the Upper Devonian system. According to previous studies in the Domanik formation sedimentary complexes of the Volga-Ural oil and gas province, two types of rocks are distinguished - the Domanikites themselves and Domanikoids. Domanikites contain from 5 to 20% organic matter. Both types of carbonaceous rocks have a practically similar lithological composition. The difference between them lies in variations in siliceous component content and number of authigenic minerals. If content of very fine-grained silica was determined by primary sedimentation factors, then authigenic minerals are indicators of secondary lithogenesis processes. In this work, an attempt is made to compare organic matter content with dolomite mineralization, which is an active agent in mineral formation.

Mitigation via physiochemically enhanced primary treatment of antibiotic resistance genes in influent from a municipal wastewater treatment plant

In this study, a combined coagulation-dissolved air flotation (DAF) process was employed as enhanced primary treatment (EPT) to simultaneously reduce eleven ARGs (tetA, tetM, tetQ, tetX, sul1, sul2, qnrD, ermB, blaTEM, aac(6′)-lb-cr, floR), class 1 integrons-integrase gene (intI1) and common pollutants in the influent of a WWTP and then compared to primary sedimentation alone. In the combined coagulation-DAF process, the optimum doses of PACl, FeCl3 and Al2(SO4)3 required to achieve a removal efficiency exceeding 90% of total suspended solids (TSS) were 25 mg/L, 75 mg/L and 100 mg/L, respectively. The log removal of all quantified ARGs treated by the combined coagulation-DAF process with the three coagulants exceeded 0.44-log, a higher removal efficiency of ARGs compared to primary sedimentation alone (0.03-log). Among the three coagulants, FeCl3 showed the highest log reduction for targeted ARGs. In addition, the three coagulants showed similar capabilities to non-selectively and modestly decrease most ARGs. Most ARGs and intl1 demonstrated strongly negative correlations with the removal efficiencies of physicochemical parameters in the treated wastewater, implying that co-removal of colloidal matter, solids, phosphate, ammonium and organic matter played a crucial role in reduction of ARGs during the combined coagulation-DAF process. Particularly, strong correlations were observed between the reduction of total phosphorus (TP) and ARGs, indicating that TP may provide a suitable proxy for reduction of ARGs in this process. Despite handling influent comprised of ARGs and pollutants of high levels and diverse types, the combined coagulation-DAF process led to improved removal of ARGs along with colloidal substances. Thus, the results demonstrate the potential of a combined coagulation-DAF process to reduce ARGs flowing into WWTPs.

Assessing the potential of enhanced primary clarification to manage fats, oils and grease (FOG) at wastewater treatment works

Daily, sewage treatment works (STWs) receive large volumes of fats, oils and greases (FOG), by-products of food preparation. To increase FOG removal at STW, conventional primary sedimentation tanks (PSTs) can be enhanced using chemical coagulant or through dissolved air flotation (DAF) techniques. This work aimed to assess the potential benefits of enhanced primary treatment for FOG removal through an energy and costs analysis. To achieve this, a five-year sampling programme was conducted monthly at 15 STWs measuring FOG concentrations in crude and settled sewage (i.e. after primary treatment). In addition, two DAF pilot systems were trialled for four months and their performance, in terms of FOG removal, was assessed and compared to that of a control primary clarifier. Across the 15 STWs, influent FOG concentrations were found at 57 ± 11 mg.L−1. Chemical coagulants dosed prior to PSTs increased FOG removal rates on average to 71% whilst traditional sedimentation only achieved 50% removal. Effluent FOG concentrations were found between 12–22 mg.L−1 and 19–36 mg.L−1 respectively. By contrast, DAF achieved FOG effluent concentrations on average at 10 ± 4 mg.L−1 corresponding to 74% removal from a relatively low influent concentration of 40 ± 30 mg.L−1. Thus, enhanced primary treatments have the potential to reduce organic load to secondary treatment and increase energy generation through anaerobic digestion. The overall net energy balance was estimated at 2269 MWh.year−1 for the DAF compared to 3445 MWh.year−1 for the chemically-enhanced PST making it a less financially attractive alternative. Yet, in the case where the works require upgrading to accommodate flow or load increases, DAF appeared as a sensible option over sedimentation offering significantly lower capital costs and footprint. In relation to FOG management, upgrading all STWs is not realistic and will require understanding where the benefits would be the highest.

Effect of treated sewage characteristics on duckweed biomass production and microbial communities

Duckweed biomass production in a duckweed pond fed with three differently treated sewage (i.e. sewage treated by primary sedimentation (PS); conventional activated sludge process (CAS); and downflow hanging sponge process (DHS)) was evaluated in order to assess the effects of water quality on biomass yield. Higher and stable biomass production was observed when the duckweed pond was fed with PS or DHS-effluent than with CAS-effluent, evidently due to the difference in nutrient loads. Availability of nutrients, especially phosphorus, affected the biomass production rate: higher the nutrient, faster the production. Microbial community analysis revealed that the members of Rhizobiales were likely to contribute to stable and high biomass growth. From the results of the study, a sewage treatment system consisting of a primary sedimentation followed by a duckweed pond and a tertiary treatment unit can be proposed to maximize biomass production without compromising treatment objectives. Size and operational parameters of the duckweed pond should be determined primarily based on the nutrient availability in the influent water to maximize duckweed growth.

Characteristics of flow regime adjustment enhancing carbon source recovery in activated primary sedimentation tank

In this study, different numbers of baffles were arranged in settling zone of an activated primary sedimentation tank (APST) to adjust the flow regime of sewage, and the characteristics of flow regime adjustment enhancing carbon source recovery in the APST were explored. The results showed that, compared with the APST without baffles, setting one baffle at the front end of settling zone led to the lowest sedimentation loss of soluble chemical oxygen in the settling zone, and the SCOD and volatile fatty acid concentrations in the effluent increased by 52 mg/L and 4.49 mg/L, respectively, furthermore, the SCOD/total nitrogen (TN), and SCOD/total phosphorus (TP) in the effluent also increased by 22.47%, and 11.95%, respectively. To evaluate the mechanism of setting baffles for carbon source recovery, the numerical simulation of flow regime adjustment was utilized. The results showed that, under the condition of setting one baffle, three large recirculation zones were formed which increased the probability of collision and friction between particulates to avoid the dissolved carbon that had been desorbed in the mechanical agitation zone from being re-adsorbed and settling in the settling zone. Moreover, the baffle changed the streamlines of sewage, thereby resuspending more small carbon sources that had already settled and increasing the carbon source content of effluent. Thus, this study provided a new method of adjusting sewage flow regime in APST for enhancing the efficiency of carbon source recovery which could help improving biological nitrogen and phosphorus removal in wastewater treatment plants.

Innovative methods of wastewater treatment

The experience of usage of sewage treatment plants has shown that if we desist from the usage of primary settlements of domestic wastewater, we solve a problem with thickening, processing, transportation and placement of raw sludge. Of course, the grates for screening the waste and sand traps for removal of mineral pollutions from wastewater is still very important part of the treatment facilities. If we desist from the usage of primary settlements, we should pay great attention to the modernization and intensification of the work of sand traps and grates. Unlike with a raw sludge, waste from grates and sand mixture from sand traps can be easily recovered in an ordinary urban landfill with a solid household waste. The most part of Western countries stop to use primary sedimentation of municipal wastewater; the Russian Federation still employ this method. At the same time, the residual floc can be completely mineralized by active sludge.

Fate and driving factors of antibiotic resistance genes in an integrated swine wastewater treatment system: From wastewater to soil

Swine wastewater (SW) represents an important source of antibiotic resistance genes (ARGs) in the environment. However, few studies have assessed the occurrence and removal of ARGs in the whole wastewater treatment process followed by its farmland application. This study investigated the ARGs profiles in an integrated SW treatment system and its receiving soil, as well as their relationships with SW parameters and bacterial communities. Results revealed that sulfonamide, tetracycline and aminoglycoside resistance genes were dominant in SW. The relative abundance of total ARGs in SW was reduced by 84% after the treatments. Among the SW treatment units, anaerobic digestion, primary sedimentation and constructed wetland contributed to ARGs removal while secondary sedimentation increased the total ARGs abundance. Farmland irrigation of the treated SW resulted in enrichment of persistent ARGs in the receiving soil, which might be attributed to the propagation of potential bacterial hosts and high horizontal gene transferability. Redundancy analysis indicated that the relative abundance of total ARGs was significantly correlated with total nitrogen, total phosphorus, antibiotics and bacterial communities. The shift in bacterial community was the major driving factor for ARGs alteration during SW treatment process. Our results highlight the effect of treated SW irrigation on the antibiotic resistome in agricultural environment, and can contribute in improving SW treatment system for better antibiotic resistance control.

Removal of emerging contaminants from wastewater during chemically enhanced primary sedimentation and acidogenic sludge fermentation

A novel wastewater treatment process, which couples chemically enhanced primary sedimentation (CEPS) of sewage with acidogenic fermentation of sludge in tandem, has recently been developed to improve the removal of pollutants and nutrients, and recover valuable resources such as phosphorus and organics. This study represented the first laboratory-based examination on the level and removal of the emerging contaminants, including retinoids (i.e., retinoic acids (RAs) and their metabolites) and oestrogenic endocrine disrupting chemicals (EDCs; e.g., 4-nonylphenol, bisphenol A, etc.), in sewage, sludge and its supernatant during this novel wastewater treatment process. The results showed that 65% of retinoids and 73% of EDCs were removed from sewage after aluminum (Al) based CEPS, while 80% of retinoids and 72% of EDCs were removed after iron (Fe) based CEPS. After acidogenic fermentation of the CEPS sludge, 50% and 58% of retinoids, and 50% and 47% of EDCs were further removed in the supernatants of Al-sludge and Fe-sludge, respectively. While there were comparable removals for these two classes of emerging contaminants during Al- and Fe-based CEPS and sludge fermentation, Fe-based CEPS of sewage and sludge fermentation should be preferentially considered, given the relatively lower production of Fe-sludge and lower accumulation of retinoids in Fe-sludge. The levels of retinoids and EDCs in the supernatant and sludge changed during acidogenic fermentation of Fe-sludge. The removals of at-4-oxo-RA (i.e., the dominant retinoid) and bisphenol A (i.e., the dominant EDC) in the supernatant followed the pseudo first-order reaction model, with a half-life of 1.62 days (in the first two days) and 1.55 days (in the whole experiment of seven days), respectively. The results demonstrated the effective removal of emerging contaminants from the sewage and the supernatant during the CEPS and acidogenic sludge fermentation.

Sustainable design of large wastewater treatment plants considering multi-criteria decision analysis and stakeholders’ involvement

The typical treatment scheme of a large municipal wastewater treatment plant (LWWTP) is almost always the result of design based on technical and economic criteria. Once a threshold in terms of population equivalent (PE) is reached, it is possible that additional sludge thermal treatment might be required. Aspects such as greenhouse gas (GHG) emissions and land use for the construction of the WWTP or the service landfill are considered marginal in current design practice; in a world that requires increasingly attention to the environment, these criteria cannot be ignored when defining the treatment scheme of a LWWTP. With the intent of providing a sustainable approach to design, this study aims to identify the best treatment scheme for a LWWTP with a 720,000 PE size. Methodologically, the study involves the development of an approach based on multi-criteria decision analysis (MCDA). Six alternative treatment schemes were considered; two simplified schemes, without primary sedimentation, with extended aeration activated sludge processes and aerobic sludge stabilization; four full schemes, with primary sedimentation and anaerobic sludge digestion. Some schemes differ for the organic loading rate applied; others for the use of sludge incineration. Subsequently, six evaluation criteria (ECs) such as GHG emissions, electricity consumption, running costs, WWTP planimetric area, surface for the service landfill, as well as WWTP as biorefinery have been considered. The weighting of the ECs involved the participation of the main stakeholders in such a decision-making process, following a bottom-up approach. The resolution of the MCDA problem allowed the identification of the full scheme based on primary sedimentation, biological activated sludge at low organic load (0.210 kgBOD5/kgVSS/d) and anaerobic sludge digestion as the best solution. The sensitivity analysis, able to indirectly take into account the multitude of decision makers involved, allowed corroborating the results. The obtained treatment scheme was different from that generally adopted in current design practice for LWWTPs.

Обґрунтування доцільності впровадження усереднювачів в технологію очистки господарсько-побутових стічних вод

The inflows of municipal sewages discharged to wastewater treatment plants for full biological treatment can vary widely throughout the day. Therefore, one of the ways of optimizing the operation of wastewater treatment plants is the use of regulating tanks – equalization basins, providing the possibility of uniform supply of wastewater with averaged concentration. The purpose of the paper is to substantiate the feasibility of using equalization basins in the technological cycle of complete biological treatment of household wastewaters. According to the analysis of technological data of the Livoberezhnna Aeration Station (LAS) located in Dnipro City the sewage inflow rates at treatment plant have significant daily variations. In this regard, there is a need to implement a separate technological operation to equalize the water inflow before the primary sedimentation tanks and aeration tanks in order to normalize the flow and average concentration of pollutants. On the basis of the initial data of qualitative and quantitative indicators of water samples chemical analysis the load of biochemical oxygen demand (BOD) at the treatment plant was calculated. The volume of the equalization basin is determined according to the methodology widely used in American universities and engineering companies in the USA. The results of calculations of wastewater averaging according to BOD indicate the effect of equalization of pollutant concentrations during the day. Thus, the ratios of BOD load values for wastewater treatment without equalization and with equalization basins are: maximum to minimum — 25,82 and 2,05; minimum to average — 0,08 and 0,62; maximum to average — 2,06 and 1,27 respectively. It is established that the average wastewater outflow in the volume of 0,307 m3/s allows avoid overloading by BOD concentrations, in contrast to the actual inflow, the volume of which can fluctuate during the day.

Total mercury and methylmercury migration and transformation in an A2/O wastewater treatment plant

Municipal wastewater treatment plants (MWTPs) serve an essential role in reducing mercury (Hg) pollution. However, few studies quantified the transport and transformation of Hg through MWTPs, particularly plants based on the anaerobic-anoxic-aerobic (A2/O) process. Here, we present a mass balance for total mercury (THg) and total methylmercury (TMeHg) at the plant, and investigate the influence of pH, temperature, and dissolved oxygen on the occurrence and fate of methylmercury (MeHg) in the system. The concentrations of the THg and TMeHg in the raw sewage were 40.3 ± 26.6 ng/L (4.3 ± 2.7 g/day) and 1.9 ± 0.6 ng/L (193 ± 58 mg/day), respectively. Their concentrations in the plant's effluent water were 7.4 ± 1.5 ng/L (0.74 ± 0.2 g/day) and 0.04 ± 0.01 ng/L (3.9 ± 1.0 mg/day), corresponding to decreases of ~82% for THg and ~98% for TMeHg. Within the plant, only ~10% of the THg was removed with primary sedimentation, as Hg in the raw sewage was predominately in dissolved form. In contrast, a significant portion of TMeHg (~43%) was associated with incoming particulate matter. Much of the remaining Hg was removed in subsequent A2/O process and secondary clarifiers, with a ~78% of the THg entering the plant transferring to the dewatered sludge (concentration 1.05 ± 0.28 μg/g; 3.2 ± 0.8 g/day). These same steps decreased TMeHg in the water by ~95%, with <10% of that reduction being TMeHg transferred to the sludge (concentration 2.1 ± 1.1 ng/g; 6.2 ± 3.3 mg/day), suggesting >90% TMeHg degradation. In addition, the most important factor that impacted the variation of TMeHg concentrations was pH, then was temperature. Dissolved oxygen showed no relationship with TMeHg and DMeHg. Overall, this study demonstrates that A2/O MWTPs effectively remove MeHg from wastewater, however, sludge remains an important potential source of Hg to the environment.

Implications of advanced wastewater treatment: Electrocoagulation and electroflocculation of effluent discharged from a wastewater treatment plant

In this research, wastewater treatment was inspected on a pilot-scale wastewater treatment plant by electrochemical techniques, electrocoagulation (EC), electroflotation (EF) and electrophoretic deposition (EPD). The wastewater samples have been characterised by applying different parameters to determine optimum working conditions of the electrocoagulation reactor. Two electrodes have been tested separately with an outflow coming from primary and secondary sedimentation tank. The outflows from these tanks are introduced in EC reactor then EC reactor efficacy is determined for the removal of chemical oxygen demand (COD), suspended solids, micropollutants and amount of coagulants in agglomerates at different current densities. The amounts of suspended solids (SS) in influent and effluent streams were determined by the membrane filtration technique. The operational applied current values range from 1–4 A in the case of COD removal by Fe and Al. While for SS aggregation the applied current ranges from 0.5–3 A and inflow rate was tested from 250 to 500 L/h. The pH of outflows increased by increasing applied current and both of these parameters were found a positive increase in the amount of SS aggregations after EC treatment. Furthermore, the COD removal efficiency was found to be 56–57 % and 12–18 % in case Fe and Al electrode respectively after EC treatment. The results showed that applied current is the most effective parameter, whereas the aluminium electrodes have produced more amounts of flocs and bubbles in comparison to iron electrodes at similar amount of current density.

Composition of Modern Dust and Holocene Aeolian Sediments in Archaeological Structures of the Southern Levant

Archaeological structures are often filled with sediments and may serve as effective dust traps. The physical parameters and chemical composition of archaeological soils in hilltop ruins, ancient runoff-collecting terraces, and cleanout spoils of cisterns were determined in the Petra region in southern Jordan and the Northern Negev in Israel. Different types of ruins are characterized by certain soil structures, but could not be distinguished with regard to substrate composition. This reflects a predominance of aeolian processes for primary sedimentation, while fluvial processes seem to only re-distribute aeolian material. In the Petra region, the physical and chemical properties of all archaeological soils show a significant local contribution from associated weathered rocks. Compared to modern settled dust, archaeological soils in Southern Jordan are enriched with various major and trace elements associated with clays and oxide coatings of fine silt particles. This seems connected with preferential fixation of silt and clay by surface crusts, and a role of moisture in sedimentation processes as calcareous silt was found to be deposited in greater amounts when associated with precipitation. In contrast, the contribution of rocks is negligible in the Negev due to greater rock hardness and abundant biological crusts that seal surfaces. Archaeological soils in the Negev are chemically similar to current settled dust, which consists of complex mixtures of local and remote sources, including significant portions of recycled material from paleosols. Archaeological soils are archives of Holocene dust sources and aeolian sedimentation processes, with accretion rates exceeding those of Pleistocene hilltop loess in the Negev. Comparison with Pleistocene paleosols suggests that dust sources did not change significantly, but disappearance of snow could have reduced dust accumulation during the Holocene.

Ecofriendly laccases treatment to challenge micropollutants issue in municipal wastewaters

In this study, a multidisciplinary approach investigated the enzymatic degradation of micropollutants in real, not modified, municipal wastewaters of a plant located in Italy. Stir Bar Sorptive Extraction combined to Gas Chromatography-Mass Spectrometric detection (SBSE-GC-MS) was applied to profile targeted pollutants in wastewaters collected after the primary sedimentation (W1) and the final effluent (W2). Fifteen compounds were detected at ng/L - μg/L, including pesticides, personal care products (PCPs) and drugs. The most abundant micropollutants were bis(2-ethylhexyl) phthalate, diethyl phthalate and ketoprofen. Laccases of Trametes pubescens MUT 2400 were very active against all the target micropollutants: except few cases, their concentration was reduced more than 60%. Chemical analysis and environmental risk do not always come together. To verify whether the treated wastewaters can represent a stressor for the aquatic ecosystem, toxicity was also evaluated. Raphidocelis subcapitata and Lepidium sativum tests showed a clear ecotoxicity reduction, even though they did not evenly respond. Two in vitro tests (E-screen test and MELN assay) were used to evaluate the estrogenic activity. Treatments already operating in the plant (e.g. activated sludge) partially reduced the estradiol equivalent concentration, and it was almost negligible after the laccases treatment. The results of this study suggest that laccases of T. pubescens are promising biocatalysts for the micropollutants transformation in wastewaters and surface waters.

Analysis and Design of Sewage Treatment Plant: A Case Study Atnagore

The main objective of this study is to carry out to design of a sewage treatment plant for a Nagore and Nagore district, because it has been one of the developing pilgrimage places. Due to steady increase of increasing population, there will be more generation of domestic and municipal sewage. Sewage produces obnoxious smell which causes disease to all creatures. To avoid this problem, proper treatments is necessary before disposal to land by not throwing sewage directly to natural resources and reuse the treated water that ultimately reduces the overall demand of fresh water. Its objective is to produce an environmental safe fluid waste and solid waste suitable for disposal or reuse. In one day the total sewage generated was estimated 5 MLD considering the projected population of Nagore town for the next 30 years? Consequently this paper focuses on the sewage generation in the Nagore area based on the population and sewage treatment plant is designed accordingly. It is proposed to design the various components of sewage treatment plant considering the various standards and permissible limits of treated sewage water. The various components of sewage treatment plant are screening, grit chamber, primary sedimentation tank, biological reactor, secondary clarifier, activated sludge tank and drying beds.

Evaluation of a domestic wastewater treatment plant at an intermediate city in Cochabamba, Bolivia

Abstract This study aims to determine the seasonal variability in the performance of a medium size population wastewater treatment plant (WWTP) in Bolivia. The semi-arid area where the WWTP is located is characterized as agricultural land, with an annual rainfall of 500 mm and a mean temperature of 17 °C. The WWTP is built up of five modules, each one comprising two treatment trains composed of an upflow anaerobic sludge blanket (UASB) reactor and horizontal gravel filter. The performance of the full process has been determined based on water quantity and quality. Seven monitoring campaigns of chemical and physical wastewater characteristics were performed from March to December 2017. The measured effluent showed average removal efficiencies of 83 ± 8% and 37 ± 60% for total chemical oxygen demand (COD) and total suspended solids (TSS), respectively. The treatment system has proven to be efficient to remove organic matter and TSS, despite the occurrence of high COD and total solids (TS) influent concentrations, the accumulation of solids at all the processes and the variability of flow and temperature inside the UASB reactors. In order to improve further this efficiency, it is recommended to implement a primary sedimentation unit as a pretreatment for the UASB system that would help to homogenize both the flow and the quality of the influent.

Chemically enhanced primary sedimentation and acidogenesis of organics in sludge for enhanced nitrogen removal in wastewater treatment

Abstract Ferric iron-based chemically enhanced primary sedimentation (CEPS) can remove over 70% of organics from municipal wastewater into sludge, and acidogenic fermentation converts 27.9% of solid organic substances in the CEPS sludge into soluble ones, mostly in the form of volatile fatty acids. In this study, the CEPS sludge supernatant after fermentation (CEPS-FL) was studied as an organic carbon source for biological denitrification, in comparison with the common external carbon sources of methanol (CH3OH), sodium acetate (NaAc), and sodium propionate (NaPr). The specific denitrification rates of NaAc, NaPr, and CEPS-FL were 701.3, 449.8, and 410.3 g N·kg VSS−1·d−1, respectively, obviously higher than the value of CH3OH (237.2 g N·kg VSS−1·d−1). During heterotrophic denitrification, lower N2O yields were observed in VFAs-based denitrification reactors (0.53% of NaAc, 1.11% of NaPr, and 1.14% of CEPS-FL) than in the reactor fed with CH3OH (3.42%). The bacterial community of the denitrification sludge was significantly affected by the type of carbon sources. The sludge fed with CEPS-FL had a greater alpha diversity than that fed with pure organic carbons, with the dominance of Zoogloea (14.7%), Alicycliphilus (7.6%), and Thauera (6.2%). Based on the mass balance of CEPS-fermentation-denitrification combination, the ammonium-nitrogen in the CEPS-FL would not affect the overall nitrogen removal performance. In comparison with the municipal wastewater treatment supplemented with CH3OH or NaAc as the external carbon source for improved nitrogen removal, the operating cost of this combined system can be considerably lower. Overall, a small modification in primary sedimentation by CEPS in combination with the sludge fermentation would not only decrease the organic load on the subsequent biological treatment and significantly improve the nitrogen removal performance, but also provide an effective, chemical-saving, and energy-efficient way for wastewater treatment.

Carbon source and phosphorus recovery from iron-enhanced primary sludge via anaerobic fermentation and sulfate reduction: Performance and future application

Anaerobic fermentation and sulfate reduction (AF-SR) was firstly used for recovery of carbon sources and phosphorus from Fe-enhanced primary sludge (Fe-sludge). With FeCl3 dosage of 30 mg Fe/L, 63.0% of the chemical oxygen demand (COD) and 97.3% of the phosphorus were concentrated from sewage into Fe-sludge. Batch anaerobic fermentation tests of Fe-sludge with and without sulfate addition (AF-SR and control) were performed. The results showed that volatile fatty acid concentrations of the control and AF-SR were 211.0 and 270.2 mg COD/g volatile suspended solids, respectively. Furthermore, 33.2% (control) and 56.2% (AF-SR) of the total phosphorus in Fe-sludge was released. The recovery performances of carbon source and phosphorus were calculated based on struvite precipitation. The available carbon source of the AF-SR system was 44.5% higher than that of the control. A novel integrated wastewater and sludge treatment process based on chemically enhanced primary sedimentation and AF-SR is proposed for future application.

Operation strategy of cubic-meter scale microbial electrochemistry system in a municipal wastewater treatment plant

A 1.5 m3 pilot biocathode microbial electrochemistry system (MES) is developed with separate plug-in modular design and operated in a municipal wastewater treatment plant for treating effluent of primary sedimentation tank. Comprehensive operation strategies are investigated for the operation of pilot MES and for the high-efficiency operation of further full-size MES. Controlling with wastewater distribution system, an alternating direction parallel flow mode is achieved in pilot biocathode MES at 48 h interval and prevents the substrate limitation to downstream anodes along flow path. Intermittent aeration strategy with various air-liquid (A/L) ratios is optimized to save aeration energy of biocathode. Consequently, the optimized energy requirement is only 7.3% of that in a typical activated sludge process (0.3 kWh m−3). The dynamic microbial separator in pilot MES effectively blocks the oxygen leakage from cathode to anode compartment under tested A/L ratios (2.9–40) and enables aeration process to mainly affect biocathode performance. The incomplete polytetrafluoroethylene-coated (PTFE-coated) carbon brushes are well performed as biocathodes of pilot MES, improving the maximum power output by 15% under oxygen-limited condition. The hydrophobic surface provides oxygen source for cathode reduction due to the high air-affinity and supports a great amount of biomass on cathode brushes.

Alkaline fermentation promotes organics and phosphorus recovery from polyaluminum chloride-enhanced primary sedimentation sludge

In this study, alkaline fermentation was applied to promote organics and P recovery from polyaluminum chloride (PACl)-enhanced primary sedimentation sludge. Coagulant results demonstrated that the optimum PACl dosage of 100 mg/L resulted in the effective concentration of 73% of organic matter and 90% of P from wastewater into sludge. Batch fermentation results highlighted the ability of alkaline fermentation in improving the biodegradability of PACl sludge. More specifically, at pH 11, 43.3% of soluble organics and 36.49% of P were released to the fermentation supernatant. Furthermore, P fractionation fermented sludge results revealed that partial Al-P dissolution and organic phosphorus hydrolysis were the main drivers of the released P. Finally, at pH 11, 85% of P was recovered as magnesium ammonium phosphate from the fermentation supernatant at the 2:1 Mg/P molar ratio. In conclusion, 24.9% of organics and 27.9% of P from raw wastewater were converted to valuable products via alkaline fermentation.