Conventional Municipal Wastewater Treatment Research Articles

Simultaneous enhanced removal of pharmaceuticals and hormone from wastewaters using series combinations of ultra-violet irradiation, bioremediation, and adsorption technologies

Pharmaceuticals and hormones presence in effluent of conventional municipal wastewater treatment plants (WWTPs) have been widely reported. Medicinal mushrooms such as Ganoderma species and bentonite clay were recently found to have promising results in wastewater treatment with potential advantages in the removal of pharmaceuticals. Here we investigated a hybrid treatment comprising of three separate processes (no chemicals) i.e., UV irradiation, biological, adsorption (bentonite + dolomite) in a series to enhance the simultaneous removal pharmaceuticals and hormone from wastewaters (real and synthetic). In this study, fungal species Ganoderma lucidum (GLSB) and Ganoderma neo-japonicum (GJSG) are used separately in bioreactors. The work investigated removal efficiencies of four (4) pharmaceuticals and a hormone. The results showed that all investigated pharmaceuticals and hormone were removed in hybrid treatment during 54.5 h treatment. Both GLSB and GJSG reactor series treatments achieved maximum removal in both synthetic and real domestic wastewater. Overall, this study provides promising suggestions for the upgrade and design of WWTPs to simultaneous complete removal of pharmaceuticals and hormone. Present study is a beginning for future development of sustainable tertiary hybrid treatment process in addition to existing WWTPs processes to completely remove the emerging pollutants.

Anaerobic Membrane Bioreactors for Municipal Wastewater Treatment, Sewage Sludge Digestion and Biogas Upgrading: A Review

Anaerobic membrane bioreactors (AnMBRs) are formed through the combination of anaerobic digestion and membrane technology. The upgraded technology separates SRT from HRT in the anaerobic digester, shortening the treatment period, reducing the digester’s volume and improving effluent quality. Furthermore, AnMBRs have a strong tolerance for the existing forms of objects and can handle liquids, high-solid materials and gases. Up to now, AnMBRs have been utilized in the treatment of various types of industrial and municipal wastewater, organic solid waste and also biogas upgrading, and they have achieved excellent performance. However, there are few studies which have discussed their multiple utilization, especially following the flow of wastewater treatment. This study summarizes the application of AnMBRs in their diverse roles in the municipal wastewater treatment process. The discussion revolves around energy generation and the fouling issue of AnMBRs in the treatment of municipal wastewater, the digestion of sewage sludge generated in conventional municipal wastewater treatment and the upgrading of biogas after anaerobic digestion. In addition to controlling operating parameters, strategies used to improve the treatment effectiveness are also introduced. Lastly, online methods for preventing membrane fouling, which is the main operational obstacle to AnMBRs’ wider spread, are also discussed. This review aims to provide a fresh perspective on how AnMBRs are utilized in waste treatment.

Microplastic abundance and removal via an ultrafiltration system coupled to a conventional municipal wastewater treatment plant in Thailand

A wastewater treatment plant is one of the land-based sources of microplastics in freshwater environments. A conventional wastewater treatment plant alone is not designed for microplastic removal. This study evaluates the abundance and microplastic removal efficiency of a conventional wastewater treatment plant and the load daily released to water environment. It also investigates the effect of coupling a pilot-scale ultrafiltration system. Samples were collected at each unit operation by grab sampling. Sludge samples were collected from return activated sludge after the final clarifier to find microplastic pollution levels that might contaminate agricultural soil. The results showed that on average, 77 ± 7.21 particles/L were found in the influent, and 10.67 ± 3.51 particles/L were discharged with the final effluent, resulting in 86.14% overall removal efficiency in a traditional treatment system. When an ultrafiltration unit was taken into consideration, the number of microplastics in the effluent reduced to 2.33 ± 1.53 particles/L, which increased the removal efficiency up to 96.97%. The abundance of microplastic particles in sludge samples generated from the final clarifier was 2.63 ± 1.26 × 104 particles/kg (dry weight). The most dominant group was 0.05–0.5 mm, and fibers accounted for more than 60% of total microplastics at every sampling point. The results from spectroscopic analysis showed that polyethylene terephthalate (PET) was the major type of microplastics, followed by polyethylene (PE) and polypropylene (PP). This study shows that advanced technology in tertiary treatment plants could substantially remove microplastic pollution in wastewater. Moreover, the absence of primary sedimentation tank can also influence removal of microplastics.

Assessment of Microalgal-Bacterial Granular Sludge Process for Environmentally Sustainable Municipal Wastewater Treatment

The conventional municipal wastewater treatment processes are facing increasing pressures due to their huge energy consumption, significant emissions of greenhouse gases, and low resource recovery ...

Removal of Heavy Metals during Primary Treatment of Municipal Wastewater and Possibilities of Enhanced Removal: A Review

Resource reuse has become an important aspect of wastewater management. At present, use of sludge in agriculture is one of the major reuse routes. Conventional municipal wastewater treatment does not involve any designated process for removal of heavy metals, and these distribute mainly between effluent and sludge. Enhanced removal of heavy metals during primary treatment may decrease the heavy metal concentrations in both effluent and sludge from secondary treatment and promote long-term reuse of secondary sludge. This review considers heavy metal occurrence and removal during primary settling, together with possible treatment technologies for heavy metal removal in primary settlers and their theoretical performance. The variation in total heavy metal concentrations and dissolved fraction in raw municipal wastewater points to a need for site-specific assessments of appropriate technologies for improved heavy metal removal. Studies examining the heavy metal speciation beyond dissolved/particulate are few. Missing or disparate information on process parameters such as hydraulic retention time, pH and composition of return flows makes it hard to generalize the findings from studies concerning heavy metal removal in primary settlers. Coagulation/flocculation and use of low-cost sorbents were identified as the most promising methods for enhancing heavy metal removal during primary settling. Based on the available data on heavy metal speciation and removal during primary settling, sorption technologies may be most effective for enhancing the removal of Cu and Ni, while coagulation may be efficient for Cd, Cr, Cu, Pb, Zn and Hg removal (but not as efficient for Ni removal).

Fate of active pharmaceutical ingredients in a northern high-rate algal pond fed with municipal wastewater

Active pharmaceutical ingredients (APIs) are vital to human health and welfare, but following therapeutic use, they may pose a potential ecological risk if discharged into the environment. Today’s conventional municipal wastewater treatment plants are not designed to remove APIs specifically, and various techniques, preferably cost-effective and environmentally friendly, are being developed and evaluated. Microalgae-based treatment of wastewater is a sustainable and low-cost approach to remove nutrients and emerging contaminants. In this study, a North Sweden high-rate algal pond (HRAP) using municipal untreated wastewater as medium, was investigated in terms of API distribution and fate. Three six-day batches were prepared during 18 days and a total of 36 APIs were quantified within the HRAP of which 14 were removed from the aqueous phase above 50% and seven removed above 90% of their initial concentrations. Twelve APIs of a hydrophobic nature were mostly associated with the algal biomass that was harvested at the end of each batch. HRAPs treatment successfully removed 69% of studied APIs (25 of 36 studied) in six day time. The distribution of various APIs between the aqueous phase and biomass suggested that several removal mechanisms may occur, such as hydrophobicity driven removal, passive biosorption and active bioaccumulation.

Removal of emerging micropollutants from wastewater by nanofiltration and biofilm reactor (MicroStop)

AbstractCurrent wastewater treatment is not designed for the elimination of micropollutants (MP) and therefore these are released into the aquatic environment by means of the municipal wastewater. The MicroStop project investigates a combination of a fixed‐bed reactor (FBR) and a nanofiltration plant (NF) for the elimination of organic MP. NF acts as a barrier for MP while biological degradation of the pollutants is to be induced in the FBR. A simultaneous treatment of the retentate should be realized by its return to the FBR. The NF is to be supplied with energy by a large separation of organic matter in the primary clarification. The experiments showed that NF can eliminate more than 95% of the selected and detected MP on average, and therefore, this method represents a suitable barrier for these pollutants. The retentate of the NF was used to test the potential of the biological degradation in the FBR. The test results showed that a significant biological degradation of different MP took place in the FBR. The degradability of the substances could be verified by not detecting significant adsorption on sludge and fixed‐bed. For certain MP (sulfamethoxazole and carbamazepine) only little potential of biodegradation could be detected, which is confirmed by values from the literature. Apart from these two substances, the average degradation rate was 78%. The successful MP‐retention in connection with the biological degradation rates demonstrated the potential of the concept.Statement of Industrial RelevanceIt is undisputed that the conventional wastewater treatment has to be upgraded, since it is not able to eliminate residual MP. The following describes how the MicroStop‐process is able to address MP where competitive processes such as activated carbon or ozonation fail to do so: The process is able to eliminate MP comprehensively and to retain microplastics, pathogenic germs and metabolites to a large extent before they reach the environment. The retentate, which normally occurs as residue of the NF, is directly treated in the FBR. The only residue of the MicroStop‐process would be the excess sludge, which could easily be used for sludge treatment. The effluent of the process is of high quality. This could be used in other regions of the world for irrigating plants, for industrial processes or even as tap water. The potentially increased energy consumption (i.e., due to NF) is taken into account in our concept by the carbon extraction in the primary treatment. Novelty or SignificanceThe combination of NF with biological degradation of MP in a FBR represents a process that has not yet been investigated in this form.In addition, the combination with an elevated carbon extraction in the primary treatment (Powerstep‐process) represents the idea of a complete redesign of conventional municipal wastewater treatment plants.

Correlation between operating parameters and removal efficiency for chemically enhanced primary treatment system of wastewater

Background“Chemically enhanced primary treatment” (CEPT) is an approach to wastewater treatment. It can be utilized as a specially designed step in “biological” secondary treatment processes. The aim of this study is to create an empirical model of separation efficiency for wastewater chemically enhanced primary treatment.MethodsThe empirical model is undertaken using the simulation of the data obtained from pilot plant experimental studies using different types of coagulant (FeCl3, alum, lime, and Magna-floc155).The empirical modeling techniques used multivariate regression model. Different values of BOD5, COD, TSS, as well as separation efficiencies for COD and TSS were investigated in accordance to achieve final effluent results that would meet the Egyptian standards limit.ResultsMultiple regression analysis showed that removal efficiencies of COD and TSS can be predicted to be (R2 = 0.973 and 0.978, respectively).ConclusionThe present work provides an approach for using chemically enhanced primary treatment of wastewater. The obtained results showed that the empirical model can predict removal efficiencies with R2 = 0.973, and 0.978 for COD and TSS. The advantage of this model is that it would allow better process control and treatment efficiency. The results show that chemically enhanced primary treatment method can be used as an efficient method in conventional municipal wastewater treatment plants to reduce the organic load of biological treatment and enhance nutrients removal.

Electro-oxidation of secondary effluents from various wastewater plants for the removal of acetaminophen and dissolved organic matter

Electro-oxidation of acetaminophen (ACT) in three different doped secondary effluents collected from a conventional Municipal Waste Water Treatment Plant (MWWTP), a MWWTP using a membrane bioreactor (WWTP MBR) and a lab-scale MBR treating source-separated urine (Urine MBR) was investigated by electro-Fenton (EF) coupled with anodic oxidation (AO) using sub-stoichiometric titanium oxide anode (Ti4O7). After 8 h of treatment, 90 ± 15%, 76 ± 3.8% and 46 ± 1.3% of total organic carbon removal was obtained for MWWTP, MWWTP-MBR and Urine-MBR respectively, at a current intensity of 250 mA, pH of 3 and [Fe2+] = 0.2 mM. Faster degradation of ACT was observed in the WWTP MBR because of the lower amount of competitive organic matter, however, >99% degradation of ACT was obtained after 20 min for all effluents. The acute toxicity of the treated effluent was measured using Microtox® tests. Results showed an initial increase in toxicity, which could be assigned to formation of more toxic by-products than parent compounds. From 3D excitation and emission matrix fluorescence (3DEEM), different reactivity was observed according to the nature of the organic matter. Particularly, an increase of low molecular weight organic compounds fluorescence was observed during Urine MBR treatment. This could be linked to the slow decrease of the acute toxicity during Urine MBR treatment and ascribed to the formation and recalcitrance of toxic organic nitrogen and chlorinated organic by-products. By comparison, the acute toxicity of other effluents decreased much more rapidly. Finally, energy consumption was calculated according to the objective to achieve (degradation, absence of toxicity, mineralization).

A self-sustaining synergetic microalgal-bacterial granular sludge process towards energy-efficient and environmentally sustainable municipal wastewater treatment

Globally increasing concerns have been raised on the high energy consumption and greenhouse gas emissions in conventional municipal wastewater treatment processes over the past decades. In this study, a self-sustaining synergetic microalgal-bacterial granular sludge process was thus developed to address these challenges. The results showed that the microalgal-bacterial granular sludge process was capable of removing 92.69%, 96.84% and 87.16% of influent organics, ammonia and phosphorus under non-aeration conditions over a short time of 6 h. The effluent could meet the increasingly stringent discharge standards in many countries worldwide. A tight synergetic interrelationship effect between microalgae and bacteria in granules was essential for such excellent process performance. The stoichiometric and functional genes analyses further revealed that most of organic matter and nutrients were removed through microalgal and bacterial assimilations. Moreover, it was found that there existed a desirable distribution of functional species of microalgae and bacteria in microalgal-bacterial granules, which appeared to be essential for the self-sustaining synergetic reactions and stability of microalgal-bacterial granules. Consequently, this work may offer a promising engineering alternative with great potential to achieve energy-efficient and environmentally sustainable municipal wastewater treatment.

Assessment of landfill leachate biodegradability and treatability by means of allochthonous and autochthonous biomasses

The biodegradability and treatability of a young (3 years old) municipal landfill leachate was evaluated by means of chemical oxygen demand (COD) fractionation tests, based on respirometric techniques. The tests were performed using two different biomasses: one cultivated from the raw leachate (autochthonous biomass) and the other collected from a conventional municipal wastewater treatment plant after its acclimation to leachate (allochthonous biomass). The long term performances of the two biomasses were also studied. The results demonstrated that the amount of biodegradable COD in the leachate was strictly dependent on the biomass that was used to perform the fractionation tests. Using the autochthonous biomass, the amount of biodegradable organic substrate resulted in approximately 75% of the total COD, whereas it was close to 40% in the case of the allochthonous biomass, indicating the capacity of the autochthonous biomass to degrade a higher amount of organic compounds present in the leachate. The autochthonous biomass was characterized by higher biological activity and heterotrophic active fraction (14% vs 7%), whereas the activity of the allochthonous biomass was significantly affected by inhibitory compounds in the leachate, resulting in a lower respiration rate (SOUR = 13 mg O2 gVSS−1 h-1vs 37 mg O2 gVSS−1 h−1). The long-term performance of the autochthonous and allochthonous biomasses indicated that the former was more suitable for the treatment of raw landfill leachate, ensuring higher removal performance towards the organic pollutants.

Containment of a genetically modified microorganism by an activated sludge system

The effectiveness of physical, chemical and biological barriers to the diffusion of genetically modified microorganisms (GMMs) to prevent their release into the environment is currently under scrutiny worldwide because of the associated potential ecological impacts. An industrial discharge of a non-sterilized fermentation broth containing GMM biomass into a conventional municipal wastewater treatment plant would deliver the GMMs into the activated sludge system process (ASSP). The present work aimed to model and evaluate the containment capability of a small ASSP (part of a 20,000 people equivalent municipal plant) in the event of receiving GMM biomass from a medium-small biotechnological plant dedicated to the production of polyhydroxyalkanoates (3000 t/year of biopolymer). An actual GMM (Pseudomonas putida KTOY06) was injected into a bench-scale ASSP (ASSPLab) in a quantity proportional to the relative dimensions of the plants mentioned. The experimental and model results indicated that the ASSP of the target municipal treatment plant would not be capable of holding back such a sudden input of GMM; 6 h after the discharge, 11–15 % of injected GMM cells were released through the clarified stream of the ASSPLab, with the rest being gradually released over time. Since the GMM employed did not exhibit any growth in the ASSPLab, its concentration in the clarified water stream would not represent a substantial risk of release into the environment if appropriate tertiary treatments were integrated. This study confirmed the necessity of a thorough risk assessment of biotechnological processes prior to their implementation.

Recent advances in energy efficient biological treatment of municipal wastewater

Conventional municipal wastewater treatment plants based on the activated sludge process are neither energy efficient nor economical. Various technologies (e.g., anaerobic treatment, algal technology and microbial fuel cells) have been proposed or employed to transform municipal wastewater treatment plant from energy sink to either net energy producer or energy neutral. Recently, anaerobic ammonia oxidation (Anammox) technology is getting attention as an energy efficient nitrogen removal process for anaerobically-pretreated municipal wastewater. Phytoremediation through constructed wetlands is another energy efficient method to treat low-strength wastewater. The aim of this paper is to review the recent advances in these energy efficient technologies for the sustainable treatment of municipal wastewater. The advantages, limitations and application status (whether, lab-, pilot- or full-scale) along with future research perspectives of these technologies are also highlighted in this review.

Application of Bioaugmentation to Improve Pharmaceutical Wastewater Treatment Efficiency

Ecological harm and human health risks caused by environmental pollution with active pharmaceutical ingredients (API) nowadays is recognised as issue of growing concern. Widespread presence of human and veterinary API in aquatic environment clearly indicates persistence and low removal efficiency of these compounds at conventional pharmaceutical and municipal wastewater treatment plants (WWTP). Bioaugmentation of activated sludge systems with specialized microorganisms could be a powerful and environmentally friendly tool to enhance the removal efficiency of recalcitrant API. Selection of inoculum strains, that have appropriate enzymatic pathways to metabolise complex molecules of API, belonging to different therapeutic classes, is of great importance. This study evaluated the potential of pure cultures of 10 bacteria, 10 yeasts and 3 filamentous fungi previously isolated from activated sludge of pharmaceutical WWTP to degrade less investigated API – Oxytocin, Zopiclone and Meldonium dihydrate as sole carbon source and in cometabolic manner with presence of skim milk powder as additional nutrient source. Bacteria Sphingobacterium thalpophilum and filamentous fungi Fusarium solani and Fusarium udum showed very high treatment efficiency of all tested API in laboratory-scale bioaugmentation tests and were recognized as culture with high metabolic potential to be used in bioaugmentation for removal of pharmaceutical micropollutants.

Conventional wastewater treatment and reuse site practices modify bacterial community structure but do not eliminate some opportunistic pathogens in reclaimed water

Water recycling continues to expand across the United States, from areas that have access to advanced, potable-level treated reclaimed water, to those having access only to reclaimed water treated at conventional municipal wastewater treatment plants. This expansion makes it important to further characterize the microbial quality of these conventionally-treated water sources. Therefore, we used 16S rRNA gene sequencing to characterize total bacterial communities present in differentially-treated wastewater and reclaimed water (n = 67 samples) from four U.S. wastewater treatment plants and one associated spray irrigation site conducting on-site ultraviolet treatment and open-air storage. The number of observed operational taxonomic units was significantly lower (p < 0.01) in effluent, compared to influent, after conventional treatment. Effluent community structure was influenced more by treatment method than by influent community structure. The abundance of Legionella spp. increased as treatment progressed in one treatment plant that performed chlorination and in another that seasonally chlorinated. Overall, the alpha-diversity of bacterial communities in reclaimed water decreased (p < 0.01) during wastewater treatment and spray irrigation site ultraviolet treatment (p < 0.01), but increased (p < 0.01) after open-air storage at the spray irrigation site. The abundance of Legionella spp. was higher at the sprinkler system pumphouse at the spray irrigation site than in the influent from the treatment plant supplying the site. Legionella pneumophila was detected in conventionally treated effluent samples and in samples collected after ultraviolet treatment at the spray irrigation site, while Legionella feeleii persisted throughout on-site treatment at the spray irrigation site, and, along with Mycobacterium gordonae, was also detected at the sprinkler system pumphouse at the spray irrigation site. These data could inform the development of future treatment technologies and reuse guidelines that address a broader assemblage of the bacterial community of reclaimed water, resulting in reuse practices that may be more protective of public health.

Impact of Wastewater Treatment on the Prevalence of Integrons and the Genetic Diversity of Integron Gene Cassettes.

The integron platform allows the acquisition, expression, and dissemination of antibiotic resistance genes within gene cassettes. Wastewater treatment plants (WWTPs) contain abundant resistance genes; however, knowledge about the impacts of wastewater treatment on integrons and their gene cassettes is limited. In this study, by using clone library analysis and high-throughput sequencing, we investigated the abundance of class 1, 2, and 3 integrons and their corresponding gene cassettes in three urban WWTPs. Our results showed that class 1 integrons were most abundant in WWTPs and that wastewater treatment significantly reduced the abundance of all integrons. The WWTP influents harbored the highest diversity of class 1 integron gene cassettes, whereas class 3 integron gene cassettes exhibited highest diversity in activated sludge. Most of the gene cassette arrays detected in class 1 integrons were novel. Aminoglycoside, beta-lactam, and trimethoprim resistance genes were highly prevalent in class 1 integron gene cassettes, while class 3 integrons mainly carried beta-lactam resistance gene cassettes. A core class 1 integron resistance gene cassette pool persisted during wastewater treatment, implying that these resistance genes could have high potential to spread into environments through WWTPs. These data provide new insights into the impact of wastewater treatment on integron pools and highlight the need for surveillance of resistance genes within both class 1 and 3 integrons.IMPORTANCE Wastewater treatment plants represent a significant sink and transport medium for antibiotic resistance bacteria and genes spreading into environments. Integrons are important genetic elements involved in the evolution of antibiotic resistance. To better understand the impact of wastewater treatment on integrons and their gene cassette contexts, we conducted clone library construction and high-throughput sequencing to analyze gene cassette contexts for class 1 and class 3 integrons during the wastewater treatment process. This study comprehensively profiled the distribution of integrons and their gene cassettes (especially class 3 integrons) in influents, activated sludge, and effluents of conventional municipal wastewater treatment plants. We further demonstrated that while wastewater treatment significantly reduced the abundance of integrons and the diversity of associated gene cassettes, a large fraction of integrons persisted in wastewater effluents and were consequentially discharged into downstream natural environments.

Redesigning C and N mass flows for energy-neutral wastewater treatment by coagulation adsorption enhanced membrane (CAEM)-based pre-concentration process

From the perspective of mass flow, the conventional municipal wastewater treatment based on active sludge process (CAS) removes pollutants by aerobically converting organic carbon (C) into useless CO2 with excess sludge as a by-product and removing nitrogen (N) in the form of N2 by nitrification/denitrification with aeration energy and the carbon source input. To improve sustainability, in this paper, we propose a novel process based on the coagulation adsorption enhanced membrane (CAEM) method, which redesigns the C and N mass flows for energy-neutral wastewater treatment. A pilot-scale operation conducted over two months demonstrated that up to 85.6% chemical oxygen demand (COD) was rejected by CAEM, which could be directed into the anaerobic energy recovery unit in a concentrated form with high biodegradability. Meanwhile, 74.9% nitrogen was kept in the mainstream for the subsequent autotrophic deammonification. Modelling results based on steady-state mass balance and stoichiometric calculations indicated the changes in the C and N mass flows induced by CAEM. The amount of organics (COD) used for energy production increased remarkably compared with that in the CAS process. Combined with mainstream deammonification, this CAEM-based process also avoided the COD consumed by denitrification and heterotrophic oxidation, leading to less aeration and energy consumption (0.22 kWh/t in the CAS process vs. 0.05 kWh/t in the CAEM-based process). The proposed CAEM-based process redesigned a larger C mass flow to the anaerobic energy recovery unit than energy-intensive aerobic oxidation and more N removal by autotrophic deammonification than by heterotrophic deammonification, making it feasible to achieve energy neutrality.

Occurrence and Fate of Antibiotics in the Aqueous Environment and Their Removal by Constructed Wetlands in China: A review

Overuse of antibiotics has become a serious ecological problem worldwide. There is growing concern that antibiotics are losing their effectiveness due to an increased antibiotic resistance in bacteria. During the last twenty years, consumption of antibiotics has increased rapidly in China, which has been cited as one of the world's worst abusers of antibiotics. This review summarizes the current state of antibiotic contamination in China's three major rivers (the Yangtze River, Yellow River, and Pearl River) and illustrates the occurrence and fate of antibiotics in conventional municipal wastewater treatment plants (WWTPs). The analytical data indicate that traditional WWTPs cannot completely remove these concerned pharmaceuticals, as seen in the large difference between the distribution coefficient (Kd) and the uneven removal efficiency of various types of antibiotics. Although constructed wetlands (CWs) offer a potential way to remove these antibiotics from water supplies, knowledge of their mechanisms is limited. There are four main factors affecting the performance of CWs used for the treatment of antibiotics in water supplies, the types and configurations of CWs, hydraulic load rates, substrates, and plants and microorganisms. Further researches focusing on these factors are needed to improve the removal efficiency of antibiotics in CWs.

Impact of organic polyelectrolytes on coagulation of source-separated black water

ABSTRACTHousehold wastewater is originated from common people's activities and has a potential harmful impact on the environment if discharged directly without proper treatment. Toilet wastewater or black water (BW) contains urine, faeces, toilet paper and flushing water and it contains the majority of pollutants obtained from a single household. In this study, the focus was on BW treatment using chemical methods. The main goal of current research was to define the possibility and applicability of conventional coagulants and flocculants in direct chemical treatment of vacuum-collected BW to remove particles, organic matter and phosphorous. After the definition of dosing ranges, based on the equivalent doses in conventional municipal and industrial wastewater treatment data, aluminium and iron coagulants, organic polyelectrolytes (polymers with anionic, neutral and cationic charge with different molecular weights) and their various combinations were tested using the well-known jar-test laboratory method to study aggregation and solid–liquid separation processes in raw BW. The most important process parameter during the coagulation was pH level, dependent on the type and doses of metal salts. Some side processes were found to occur while using iron-based coagulants. Dosing of either single coagulants or single polymers did not give satisfactory results, while a combination of aluminium salts and cationic polymers showed high removal rates in total suspended solids, total chemical oxygen demand and ortho-phosphates, reaching 97.8%, 92% and 98.6%, respectively, with the optimal doses of chemicals. Cationic polymers with the lowest molecular weight and highest charge density were the most efficient in combination with aluminium coagulants.

Integration of an innovative biological treatment with physical or chemical disinfection for wastewater reuse

In the present paper, the effectiveness of a Sequencing Batch Biofilter Granular Reactor (SBBGR) and its integration with different disinfection strategies (UV irradiation, peracetic acid) for producing an effluent suitable for agricultural use was evaluated. The plant treated raw domestic sewage, and its performances were evaluated in terms of the removal efficiency of a wide group of physical, chemical and microbiological parameters. The SBBGR resulted really efficient in removing suspended solids, COD and nitrogen with an average effluent concentration of 5, 32 and 10mg/L, respectively. Lower removal efficiency was observed for phosphorus with an average concentration in the effluent of 3mg/L. Plant effluent was also characterized by an average electrical conductivity and sodium adsorption ratio of 680μS/cm and 2.9, respectively. Therefore, according to these gross parameters, the SBBGR effluent was conformed to the national standards required in Italy for agricultural reuse. Moreover, disinfection performances of the SBBGR was higher than that of conventional municipal wastewater treatment plants and met the quality criteria suggested by WHO (Escherichia coli<1000CFU/100mL) for agricultural reuse. In particular, the biological treatment by SBBGR removed 3.8±0.4logunits of Giardia lamblia, 2.8±0.8logunits of E. coli, 2.5±0.7logunits of total coliforms, 2.0±0.3logunits of Clostridium perfringens, 2.0±0.4logunits of Cryptosporidium parvum and 1.7±0.7logunits of Somatic coliphages. The investigated disinfection processes (UV and peracetic acid) resulted very effective for total coliforms, E. coli and somatic coliphages. In particular, a UV radiation and peracetic acid doses of 40mJ/cm2 and 1mg/L respectively reduced E. coli content in the effluent below the limit for agricultural reuse in Italy (10CFU/100mL). Conversely, they were both ineffective on C. perfringens spores.