Philosophiae Doctor - PhD / Wastewater is normally composed of a mixture of pollutants. The type and composition of pollutants in a particular wastewater depend on the source of origin. The source and characteristics of a particular wastewater determine the ideal method of sewage treatment. Specific treatment techniques are effective in the removal of certain types of pollutants and may have no impact on the levels of other types of pollutants. Therefore, a combination of treatments and assessment of the quality of effluent before release into the environment is normally recommended. The assessment of effluent can be achieved by various techniques including chemical analysis and biological assays. Chemical analyses are commonly employed; however, they often pose detection problems and are considered to be uneconomical.

Membrane bioreactors (MBRs) offer promising solution for wastewater treatment and reuse to address the problem of water scarcity. Nevertheless, this technology is still facing challenges associated with membrane biofouling. This phenomenon has been mainly investigated in lab-scale MBRs with little or no insight on biofouling in full-scale MBR plants. Furthermore, the temporal dynamics of biofouling microbial communities and their extracellular polymeric substances (EPS) are less studied. Herein, a multidisciplinary approach was adopted to address the above knowledge gaps in lab- and full-scale MBRs. In the full-scale MBR study, 16S rRNA gene pyrosequencing with multivariate statistical analysis revealed that the early and mature biofilm communities from five full-scale MBRs differed significantly from the source community (i.e. activated sludge), and random immigration of species from the source community was unlikely to shape the community structure of biofilms. Also, a core biofouling community was shared between the five MBR plants sampled despite differences in their operating conditions. In the lab-scale MBR studies, temporal dynamics of microbial communities and their EPS products were monitored on different hydrophobic and hydrophilic membranes during 30 days. At the early stages of filtration (1 d), the same early colonizers belonging to the class Betaproteobacteria were identified on all the membranes. However, their relative abundance decreased on day 20 and 30, and sequence reads belonging to the phylum Firmicutes and Chlorobi became dominant on all the membranes on day 20 and 30. In addition, the intrinsic membrane characteristic did not select any specific EPS fractions at the initial stages of filtration and the same EPS foulants developed with time on the hydrophobic and hydrophilic membranes. Our results indicated that the membrane surface characteristics did not select for specific biofouling communities or EPS foulants, and the same early colonizers were selected from the source community (i.e. activated sludge), and then went through significant changes to form a mature biofilm. Our findings from these studies could support future research aimed at developing enhanced biological-based strategies to control biofouling in MBRs.

Shortage of potable water is a problem that affects many nations in the world and it will aggravate in a near future if pertinent actions are not carried out. Decrease in consumption, improvements in water distribution systems to avoid losses and more efficient water treatment processes are some actions that can be implemented to attack this problem. Membrane technology and biological processes are used in wastewater treatment to achieve high water quality standards. Some other technologies, besides water treatment, attempt to obtain energy from organic wastes present in water. In this study, a proof-of-concept was accomplished demonstrating that a Microbial Electrolysis Cell can be fully integrated with a Membrane Bioreactor to achieve wastewater treatment and harvest energy. Conductive hollow fiber membranes made of nickel functioned as both filter material for treated water reclamation and as a cathode to catalyze hydrogen production reaction. The produced hydrogen was subsequently converted into methane by hydrogenotrophic methanogens. Organic removal was 98.9% irrespective of operation mode. Maximum volumetric hydrogen production rate was 0.2 m3/m3d, while maximum current density achieved was 6.1 A/m2 (based on cathode surface area). Biofouling, an unavoidable phenomenon in traditional MBRs, can be minimized in this system through self-cleaning approach of hybrid membranes by hydrogen production. The increased rate of hydrogen evolution at high applied voltage (0.9 V) reduces the membrane fouling. Improvements can be done in the system to make it as a promising net energy positive technology for the low strength wastewater treatment.

This thesis has investigated the effects of running the two full scale biogas digesters at Slottshagen wastewater treatment plant at 34 °C compared to 37 °C, in terms of process stability, biogas production and energy savings with the aim of saving energy and money by not heating the digesters as much. The main objective was to investigate whether it is at all possible to operate the biogas process at 34 °C or if the process becomes inhibited or otherwise unstable. If the process could be operated at 34 °C it might mean savings of both energy and money, provided that there is still a sufficient production of biogas.The experiment lasted for three months and investigated the short-term effects of the reduction of temperature. The process was monitored closely, and samples from the reactors were collected and analysed twice a week to ensure the stability of the biogas process. Several parameters were monitored online, the biogas production and methane content amongst others. Other parameters were calculated, such as the degree of degradation and specific methane production. This was done to ensure process stability and a sufficient production of biogas. The energy balance was calculated to evaluate if energy was saved by lowering the temperature in the digesters.The results show that the biogas process does remain stable at 34 °C while still producing a satisfactory amount of biogas during the short time of the experiment. Calculations show that both energy and money has been saved during the experiment. However, the system is largely dependent on seasonal variations, therefore further studies over a longer time period would be desirable. During the course of the thesis it has also become evident that the biogas process at Slottshagen is irregular in several aspects, and that it would be beneficial to even the process out, especially with regards to the hydraulic retention time. Making the process more even would enable further improvements to be made and simplify interpretations and comparisons of processstability data.

No description available.

The existing linear economy approach to nutrient management has clear shortcomings including high expenditures for nutrient extraction and production of fertilizer as well as additional costs for nutrient removal at downstream waste water treatment plants (WWTPs) to prevent the pollution of aquatic environments. In a circular nutrient economy, phosphorus (P) and nitrogen (N) are removed from waste streams and captured as valuable fertilizer products in order to more sustainably reuse the resources in closed-loops and simultaneously protect receiving aquatic environments from harmful P and N emissions. The overarching aim of this thesis is to understand strategic approaches for nutrient recovery from wastewater and advance membrane technologies for P and N reclamation. The studies i.) approach nutrient recovery on a system-level to recognize optimal waste streams to target for P and N separation, ii.) advance membrane-based processes for nutrient recovery, and iii.) examine the economic viability of the nutrient recovery techniques.The thesis presents a thermodynamic and energy analysis of nutrient recovery from various waste streams of fresh and hydrolyzed urine, greywater, domestic wastewater, and secondary treated wastewater effluent. The analysis revealed comparative advantages in theoretical energy intensities for P and N recovery from nutrient-dense waste streams, such as fresh and hydrolyzed urine, compared to other more dilute sources. The thesis quantifies efficiencies required by separation techniques for nutrient reclamation to be competitive with the energy requirements of the prevailing industrial fertilizer production methods, i.e., phosphate mining and nitrogen fixation by the Haber-Bosch process. The dissertation examines and advances the performance of membrane-based processes for separation and recovery of P and N from diverted human urine. Donnan dialysis (DD), an ion-exchange membrane-based process, can capture and enrich orthophosphate, HxPO4(3−x)−, from source-separated urine. This work demonstrates the transport of Cl− driver ions down a concentration gradient, across an ion-exchange membrane to set up an electrochemical potential gradient that drives the transport of target HxPO4(3−x)− in the opposite direction, enabling P capture. Importantly, H2PO4− is transported against an orthophosphate concentration gradient, which achieves uphill transport of P. The thesis also provides a framework to better understand the impact of different ions in the water matrix on P recovery potential and kinetics. The thesis presents a novel operation of membrane distillation (MD) — isothermal membrane distillation with acidic collector (IMD-AC) — to selectively recover volatile ammonia, NH3, from hydrolyzed urine. The innovative isothermal and acidic collector features, respectively, suppressed undesired water permeation and enhanced ammonia vapor flux relative to conventional membrane distillation (CMD). The elimination of water flux in IMD-AC resulted in ≈95% savings in vaporization energy consumption relative to CMD. Critically, IMD-AC achieved uphill transport of ammoniacal nitrogen, i.e., transport against a concentration gradient, demonstrating the promising potential of the technique for N recovery. The dissertation proposes an integrated bipolar membrane electrodialysis (BPM-ED), DD, and IMD-AC system to drive the separation and recovery of orthophosphate and ammoniacal nitrogen from human urine. This work elucidates the role of pH and nutrient speciation (i.e., H2PO4− versus HPO42− and NH4+ versus NH3) on the performance of DD and IMD-AC. In the proposed configuration, BPM-ED generates acids and bases in situ to strategically control the pH of urine streams to benefit DD and IMD-AC performances. Strategic pH modification can enhance orthophosphate transport and selectivity in DD as well as ammonia transport and recovery potential in IMD-AC. Importantly, the analysis quantifies comparable specific energy consumptions of the proposed integrated membrane-based process to the existing approaches to P and N management. This thesis presents a preliminary economic assessment of onsite nutrient recovery employing DD and IMD-AC for respective P and N recovery from diverted urine. The analysis reveals opportunities to utilize widely-available waste chemical streams and recovered thermal energy to improve the economic viability of nutrient recovery. The largest capital expenditures are urine diversion toilets and additional piping for source-separation. Preliminary analysis demonstrates that employing urine diversion in public sanitation rooms, as opposed to private bathrooms, can reduce these capital expenditures. Furthermore, realizing savings from avoided costs for downstream nutrient removal at centralized wastewater treatment plants in addition to fertilizer revenue can enhance the economic viability of the approach. Overall, this dissertation critically informs nutrient recovery approaches and advances membrane-based processes for P and N reclamation to facilitate a paradigm shift from an inefficient linear nutrient economy to a sustainable circular nutrient economy. The work reveals opportunities to minimize energy intensity for nutrient separation, advance the performance of membrane-based techniques for selective and energy-efficient nutrient recovery from urine, and enhance the cost-competitiveness of nutrient reclamation. The findings of this work support nutrient recovery efforts and provide important insights that can be applied to other separation and resource recovery endeavors.

Wastewater-based epidemiology can be used to analyse substances in wastewater and serve as a tool to examine the illegal drug consumption in a population. The aim of this study was to analyse concentrations of illegal drugs in wastewater from Öns wastewater treatment plant in Umeå, Sweden and i) compare concentrations of illegal drugs with previous studies from 11 and 9 years ago, ii) examine the weekly variation and iii) examine how Umeå's levels of drugs in wastewater relate to other cities in Sweden and Europe. The method used is flow proportional sampling. Three samples were collected on Monday (24-hours), Wednesday (24-hours) and a combined sample from the weekend (Friday, Saturday, Sunday, i.e., 72-hours), the samples were transferred to vials containing sodium thiosulfate (Na2S2O3), they were transported refrigerated to a laboratory in Prague, Czech Republic, where the analysis was performed. This study gives strong indications that cocaine use has increased in Umeå over the past decade and is thus in line with the increasing trend of cocaine being measured in wastewater in other European cities. This study also provides indications that the use of amphetamine has increased in Umeå over the last decade and supports previously observed trends of high amphetamine levels in Sweden in comparison with the rest of Europe. The analysis indicates higher cocaine use on weekends compared to weekdays, while amphetamine use was more evenly distributed over the week.

The aim of this work was to study the possibilities of using magnetite for phosphorus removal and recovery from wastewater. It was also aimed to investigate how the structure of magnetite influences the efficiency of adsorption and desorption of phosphorus. Methodology used in this study is literature review and laboratory experiments. The study is mainly focused on the influence of Fe(II)/Fe(III) ratio in magnetite (coefficient K) on the P removal and recovery rate. Several sets of experiments were also done to study the influence of some factors (e.g. contact time, starting concentrations, amount of base needed, etc.) on the efficiency of the processes. Study results showed that magnetite has a great potential for phosphorus removal because of its high efficiency, especially at low concentrations of input phosphorus. It was also found that the contact time and sedimentation time of the method is relatively small. Recovering of magnetite is also possible, but for its reuse additional renovation stage is needed. It was concluded that magnetite purification could be preferably used as the polishing method. It can be introduced in already existing wastewater treatment facilities and substitute some older technologies. The method seems to be easy in starting and operation; it has relatively low operational and investment costs.

Regions with a cold winter, as in the Baltic countries, have a problem to meet the nitrogen requirement in the Urban Wastewater Treatment Directive 98/15/EC. Especially in the winter season, the temperature of the influent wastewater could arrive also below 10°C and this delays the biological processes that takes place in the wastewater treatment. With the decrease of the temperature, the efficiency of nitrogen removal in the system decreases and leads to a high nitrogen loading in the effluent. The ITEST (Increased Technology and Efficiency in Sewage Treatment) project situated in Hammarby Sjöstadsverk in Stockholm has as its main aim to enhance nitrogen removal, thereby increasing the temperature in the incoming wastewater. The pilot plant ITEST is comprised of two treatment lines, one works with natural temperature influent and the other works at the temperature of 20 °C. In order to warm the incoming water a heating system, using waste heat, is used, leading to save energy. The two test lines were compared analyzing different parameters from January to May 2013. Total nitrogen, nitrate-nitrogen and ammonium-nitrogen concentrations were measured in the incoming water and in the effluent from the two treatment lines. Hence, the efficiency of the nitrogen removal was compared between the reference and the temperature line. In the period where the system was well functioning, the results show a nitrogen efficiency with a maximum of 92 % of removal of total nitrogen for the temperature line compared to only 65 % for the reference line. In the period where the system did not have any troubles the total nitrogen is under 10 mg/l, which is the limit of total nitrogen discharges specified in the Directive. Instead, for the sludge volume and the suspended solids any particular difference can be noticed from the two lines of treatment. In conclusion, in the temperature line can be noticed a great efficiency in nitrogen removal compared to the reference line.

The construction and operation of central wastewater treatment plants started around the 20th century. With the advent of rigorous membrane research and development in the middle of the 20th century, more and more wastewater plants started incorporating a Membrane BioReactor, MBR, in their design. The MBR system however is far from perfect. Membrane systems continuously foul, and if fouling is incurred for a long period of time, maintenance and cleaning costs will rise in proportion. A Fouling monitoring and prediction tool has been designed in MATLAB\Simulink. The model takes states related to membrane fouling, and calculates the membrane total resistance based on deterministic and stochastic models. The tool is capable of predicting future TMP cycles based on older TMP performance via an artificial neural network algorithm. TMP data have been synthetically generated from a validated mathematical model. Finally, an artificial neural network controller is implemented to control temperature and MLSS around their desired setpoints. The controller is able to minimize disturbances in both states in a narrow band around their desired setpoints.