One of the main obstacles impeding implementation of membrane distillation for the recovery and concentration of ammonia from swine manure is wetting caused by fouling. Due to the different types of ...fouling which can occur in a membrane system, foulants characterization is a complex problem. To elucidate the fouling mechanism, deposit morphology and composition of foulants have been determined using Scanning Electron Microscopy, X-ray Energy Dispersive Spectrometry, Attenuated Total Reflectance Infrared Spectrometry, Ion chromatography and Inductively coupled plasma-optical emission spectroscopy. Based on the analysis of fouled membranes, it is concluded that membrane fouling is dominated by organic fouling in combination with deposits of inorganic elements and microorganisms. After a week of running the membrane process without cleaning, the average fouling layer thickness was estimated to 10–15 μm. The fouling layer further results in a loss of membrane hydrophobicity. This indicates that fouling could be a severe problem for membrane distillation performance.
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•Membrane distillation performance is affected by wetting through fouling.•Fouling within first 25 h is not severe, though after one week leads to wetting.•Major foulants have been identified with SEM-EDS, ATR-FTIR, ICP-OES and IC.•Organic fouling dominates in ammonia stripping in membrane distillation.•Mechanism behind fouling explained.
Excessive livestock production in small areas poses a risk of nitrogen release to the environment and thus air and water contamination. Recovery of ammonia is necessary to avoid overfertilization, ...but manure management of untreated slurry is costly and complex. The authors discuss ammonium fertilizer recovery from manure using membrane processes and physicochemical methods including technology and energy assessments. Currently, nanofiltration, reverse osmosis, membrane distillation combined with ultrafiltration, and air stripping are the best choices. The processes rely highly on selection of appropriate pretreatment, as residual particulates will lead to fouling of membranes and stripping towers hence affect the performance greatly.
Gas sparging performances of a flat sheet and tubular polymeric membranes were investigated in 3.1 m bubble column bioreactor operated in a semi batch mode. Air–water and air–CMC (Carboxymethyl ...cellulose) solutions of 0.5, 0.75 and 1.0 % w/w were used as interacting gas–liquid mediums. CMC solutions were employed in the study to simulate rheological properties of bioreactor broth. Gas holdup, bubble size distribution, interfacial area and gas–liquid mass transfer were studied in the homogeneous bubbly flow hydrodynamic regime with superficial gas velocity (
U
G
) range of 0.0004–0.0025 m/s. The study indicated that the tubular membrane sparger produced the highest gas holdup and densely populated fine bubbles with narrow size distribution. An increase in liquid viscosity promoted a shift in bubble size distribution to large stable bubbles and smaller specific interfacial area. The tubular membrane sparger achieved greater interfacial area and an enhanced overall mass transfer coefficient (
K
L
a) by a factor of 1.2–1.9 compared to the flat sheet membrane.
Biogas plant digestate liquid fractions can be concentrated by microfiltration and ultrafiltration. Two types of microfiltration membranes (polysulphone (PS) and surface-modified polyvinylidene ...fluoride (PVDF)) were used to process digestate liquid fractions, and to assess their applicability in the recovery of particulate phosphorus, compared to an ultrafiltration membrane (polyethersulphone (PES)). Results show that membrane material, operational conditions, and pore diameter influenced the permeate flux pattern during microfiltration. The PS membranes initially had a higher tendency to foul than PVDF membranes. However, during the filtration process, as fouling built up, the permeate flux behavior of the two membranes became very similar. During the concentration of digestate liquid fractions, the microfiltration PS membrane and the ultrafiltration PES membrane achieved the highest phosphorus rejection (80% w/w), suggesting that there was a correlation between the membrane material and both the fouling trend and phosphorus rejection. A two-step basic-acidic cleaning was unable to recover the initial water flux for the fouled microfiltration membranes. In conclusion, the PS microfiltration membranes might be a good strategy for recovering phosphorus from digestate liquid fractions. Further research leading to adequate cleaning procedures, for microfiltration PS and PVDF membranes treating digestate liquid fractions though, are needed.
Swine manure is a valuable source of nitrogen, phosphorus and potassium. After solid–liquid separation, the resulting swine wastewater can be concentrated by reverse osmosis (RO) to produce a ...nitrogen–potassium rich fertilizer. However, swine wastewater has a high fouling potential and an efficient cleaning strategy is required. In this study, a semi-commercial farm scale RO spiral-wound membrane unit was fouled while processing larger volumes of swine wastewater during realistic cyclic operations over a 9-week period. Membrane cleaning was performed daily. Three different cleaning solutions, containing SDS, SDS+EDTA and NaOH were compared. About 99% of the fouling resistance could be removed by rinsing the membrane with water. Flux recoveries (FRs) above 98% were achieved for all the three cleaning solutions after cleaning. No significant differences in FR were found between the cleaning solutions. The NaOH solution thus is a good economical option for cleaning RO spiral-wound membranes fouled with swine wastewater. Soaking the membrane for 3 days in permeate water at the end of each week further improved the FR. Furthermore, a fouling resistance model for predicting the fouling rate, permeate flux decay and cleaning cycle periods based on processing time and swine wastewater conductivity was developed.
A 6-L, completely mixed anaerobic bioreactor with an external ultrafiltration membrane module was operated for 300 days to evaluate the startup and performance of an anaerobic membrane bioreactor ...(AnMBR) treating swine manure. The reactor had a successful startup at the initial loading rate of 1
g volatile solids (VS)/L/day. After a two-fold increase in loading rate followed by a sudden, two-fold increase in flow velocity through the membrane module on day 75, the performance of the AnMBR deteriorated as measured by volatile fatty acid (VFA) accumulation, decrease in pH, and decrease in biogas production. The methanogenic population dynamics in the reactor were monitored with terminal restriction fragment length polymorphism (T-RFLP). Changes in the relative levels of
Methanosarcinaceae and
Methanosaetaceae were consistent with changes in VFA concentrations, i.e., high and low levels of acetate corresponded to a high abundance of
Methanosarcinaceae and
Methanosaetaceae, respectively. The levels of hydrogenotrophic methanogens of the order of
Methanomicrobiales increased during decreased reactor performance suggesting that syntrophic interactions involving hydrogenotrophic methanogens remained intact regardless of the degree of shear in the AnMBR.
A unit performing a simple and effective way to extract active phytochemicals from the plant specimens has been developed. The unit is mobile enabling operation near the place of collection of plant ...specimens reducing waste of potential valuable phytochemicals. The design is based on counter current liquid extraction following a pretreatment, where the plant material is harvested and macerated to an extent increasing the extraction of relevant components. The pretreated plant material is fed to an inclined conveyor, counter currently with the extracting solution. The technology, known as solid/liquid extraction is developed on the basis similar to sugar extraction from sugar beets, albeit in a much more compact form. The equipment has been tested on extraction of ethereal oils from dried, stored oregano and extraction of natural compounds from freshly harvested
Artemesia
with 96% EtOH as the solvent. Preliminary results from a continuous oregano extraction show efficiency between 55% and 85% of a more ideal laboratory batch extraction of a marker compound like carvacrol, which is most abundant in the ethereal oil. The operation can be repeated with another liquid in order to extract compounds not soluble in the previous liquid and thus enabling optimal extractions of all compounds. Practically all known extracting liquids can be used by this equipment. Extracts from the extraction operation can subsequently be concentrated using a membrane distillation unit operating with hydrophobic microporous membranes for polar solvents and pervaporation membranes for unpolar solutes, where solutes with a low vapour pressure are retained, while components with higher vapour pressures permeate the membrane including water and most other solvents. The operation is performed at relatively low temperature enabling concentration of extracted solutes without deterioration due to influence of high temperatures.
The BIOREK® manure and/or organic waste treatment process based on anaerobic digestion and subsequent treatment of the effluent with conventional and novel membrane technologies is presented. The ...process consists of a mesophilic anaerobic digester coupled to a cross-flow tubular ultrafiltration membrane (ADUF). The clear, sterile effluent, rich in ammonium (N), soluble phosphates (P) and potassium (K) is processed into saleable fertiliser products and potable, demineralised water. Compared to conventional solid–liquid treatment technologies available, the proposed technology not only alleviates organic waste-handling problems, but also retains biomass, thus enabling more complete conversion of the organic substances in the feed. The present work investigates the use of a thermophilic (50–55°C) as opposed to a mesophilic digester (30–37°C). It will be shown that the UF flux increases rapidly when increasing the feed temperature mainly due to a decrease in viscosity. Further the investigation will show that the removal of volatile ammonia with membrane contactor (CM) technology is far superior to that expected by conventional steam stripping. It is found that proper UF-permeate decarbonisation and pH adjustment lead to improved ammonia transfer rates. Ammonia removal efficiencies of up to 99.9% are reached at ambient feed temperatures.
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