Abstract: As a result of the ambiguity and complexity
surrounding anaerobic digester foaming, efforts have been made by
various researchers to understand the process of anaerobic digester
foaming so as to proffer a solution that can be universally applied
rather than site specific. All attempts ranging from experimental
analysis to comparative review of other process has not fully
explained the conditions and process of foaming in anaerobic
digester. Studying the current available knowledge on foam
formation and relating it to anaerobic digester process and operating
condition, this piece of work presents a succinct and enhanced
understanding of foaming in anaerobic digesters as well as
introducing a simple method to identify the onset of anaerobic
digester foaming based on analysis of historical data from a field
scale system.
Abstract: Recovering resources from water purification sludge
(WPS) have been gradually stipulated in environmental protection
laws and regulations in many nations. Hence, reusing the WPS is
becoming an important topic, and recovering alum from WPS is one of
the many practical alternatives. Most previous research efforts have
been conducted on studying the amphoteric characteristic of aluminum
hydroxide for investigating the optimum pH range to dissolve the
Al(III) species from WPS, but it has been lack of reaction kinetics or
mechanisms related discussion. Therefore, in this investigation, water
purification sludge (WPS) solution was broken by ultrasound to make
particle size of reactants smaller, specific surface area larger.
According to the reaction kinetics, these phenomena let the dissolved
aluminum salt quantity increased and the reaction rate go faster.
Abstract: Nitrification is essential to biological processes
designed to remove ammonia and/or total nitrogen. It removes excess
nitrogenous compound in wastewater which could be very toxic to
the aquatic fauna or cause serious imbalance of such aquatic
ecosystem. Efficient nitrification is linked to an in-depth knowledge
of the structure and dynamics of the nitrifying community structure
within the wastewater treatment systems. In this study, molecular
technique was employed for characterizing the microbial structure of
activated sludge [ammonia oxidizing bacteria (AOB) and nitrite
oxidizing bacteria (NOB)] in a municipal wastewater treatment with
intention of linking it to the plant efficiency. PCR based phylogenetic
analysis was also carried out. The average operating and
environmental parameters as well as specific nitrification rate of plant
was investigated during the study. During the investigation the average temperature was 23±1.5oC.
Other operational parameters such as mixed liquor suspended solids
and chemical oxygen demand inversely correlated with ammonia
removal. The dissolved oxygen level in the plant was constantly
lower than the optimum (between 0.24 and 1.267 mg/l) during this
study. The plant was treating wastewater with influent ammonia
concentration of 31.69 and 24.47 mg/L. The influent flow rates
(ML/Day) was 96.81 during period. The dominant nitrifiers include:
Nitrosomonas spp. Nitrobacter spp. and Nitrospira spp. The AOB
had correlation with nitrification efficiency and temperature. This
study shows that the specific ammonia oxidizing rate and the specific
nitrate formation rates can serve as good indicator of the plant overall
nitrification performance.
Abstract: Anammox is a novel and promising technology that has changed the traditional concept of biological nitrogen removal. The process facilitates direct oxidation of ammonical nitrogen under anaerobic conditions with nitrite as an electron acceptor without addition of external carbon sources. The present study investigated the feasibility of Anammox Hybrid Reactor (AHR) combining the dual advantages of suspended and attached growth media for biodegradation of ammonical nitrogen in wastewater. Experimental unit consisted of 4 nos. of 5L capacity AHR inoculated with mixed seed culture containing anoxic and activated sludge (1:1). The process was established by feeding the reactors with synthetic wastewater containing NH4-H and NO2-N in the ratio 1:1 at HRT (hydraulic retention time) of 1 day. The reactors were gradually acclimated to higher ammonium concentration till it attained pseudo steady state removal at a total nitrogen concentration of 1200 mg/l. During this period, the performance of the AHR was monitored at twelve different HRTs varying from 0.25-3.0 d with increasing NLR from 0.4 to 4.8 kg N/m3d. AHR demonstrated significantly higher nitrogen removal (95.1%) at optimal HRT of 1 day. Filter media in AHR contributed an additional 27.2% ammonium removal in addition to 72% reduction in the sludge washout rate. This may be attributed to the functional mechanism of filter media which acts as a mechanical sieve and reduces the sludge washout rate many folds. This enhances the biomass retention capacity of the reactor by 25%, which is the key parameter for successful operation of high rate bioreactors. The effluent nitrate concentration, which is one of the bottlenecks of anammox process was also minimised significantly (42.3-52.3 mg/L). Process kinetics was evaluated using first order and Grau-second order models. The first-order substrate removal rate constant was found as 13.0 d-1. Model validation revealed that Grau second order model was more precise and predicted effluent nitrogen concentration with least error (1.84±10%). A new mathematical model based on mass balance was developed to predict N2 gas in AHR. The mass balance model derived from total nitrogen dictated significantly higher correlation (R2=0.986) and predicted N2 gas with least error of precision (0.12±8.49%). SEM study of biomass indicated the presence of heterogeneous population of cocci and rod shaped bacteria of average diameter varying from 1.2-1.5 mm. Owing to enhanced NRE coupled with meagre production of effluent nitrate and its ability to retain high biomass, AHR proved to be the most competitive reactor configuration for dealing with nitrogen laden wastewater.
Abstract: The disposal and the treatment of sewage sludge is an
expensive and environmentally complex problem. In this work, a
lipopeptide biosurfactant extracted from corn steep liquor was used
as ecofriendly and cost-competitive alternative for the mobilization
and bioremediation of fluorene in sewage sludge. Results have
demonstrated that this biosurfactant has the capability to mobilize
fluorene to the aqueous phase, reducing the amount of fluorene in the
sewage sludge from 484.4 mg/Kg up to 413.7 mg/Kg and 196.0
mg/Kg after 1 and 27 days respectively. Furthermore, once the
fluorene was extracted the lipopeptide biosurfactant contained in the
aqueous phase allowed the biodegradation, up to 40.5% of the initial
concentration of this polycyclic aromatic hydrocarbon.
Abstract: Currently, continuous two-phase decanter process
used for olive oil production is the more internationally widespread.
The wastewaters generated from this industry (OMW) are a real
environmental problem because of its high organic load. Among
proposed treatments for these wastewaters, advanced oxidation
technologies (Fenton, ozone, photoFenton, etc.) are the most
favourable. The direct application of these processes is somewhat
expensive. Therefore, the application of a previous stage based on a
flocculation-sedimentation operation is of high importance. In this
research five commercial flocculants (three cationic, and two anionic)
have been used to achieve the separation of phases (liquid clarifiedsludge).
For each flocculant, different concentrations (0-1000 mg/L)
have been studied. In these experiments, sludge volume formed and
the final water quality were determined. The final removal
percentages of total phenols (11.3-25.1%), COD (5.6-20.4%), total
carbon (2.3-26.5%), total organic carbon (1.50-23.8%), total nitrogen
(1.45-24.8%), and turbidity (27.9-61.4%) were determined. The
variation on electric conductivity reduction percentage (1-8%) was
also determined. Finally, the best flocculants with highest removal
percentages have been determined (QG2001 and Flocudex CS49).
Abstract: The addition of lime as Ca(OH)2 to sewage sludge to
destroy pathogens (Escherichia coli), was evaluated also in relation
to heavy metal bioavailability.
The obtained results show that the use of calcium hydroxide at the
dose of 3% effectively destroyed pathogens ensuring the stability at
high pH values over long period and the duration of the sewage
sludge stabilization. In general, lime addition decreased the total
extractability of heavy metals indicating a reduced bioavailability of
these elements. This is particularly important for a safe utilization in
agricultural soils to reduce the possible transfer of heavy metals to
the food chain.
Abstract: Brass terminal, one of the several crude oil and
petroleum products storage/handling facilities in the Niger Delta was
built in the 1980s. Activities at this site, over the years, released
crude oil into this 3 m-deep, 1500 m-long canal lying adjacent to the
terminal with oil floating on it and its sediment heavily polluted. To
ensure effective clean-up, three major activities were planned: site
characterization, bioremediation pilot plant construction and testing
and full-scale bioremediation of contaminated sediment / bank soil by
land farming. The canal was delineated into 12 lots and each
characterized, with reference to the floating oily phase, contaminated
sediment and canal bank soil. As a result of site characterization, a
pilot plant for on-site bioremediation was designed and a treatment
basin constructed for carrying out pilot bioremediation test.
Following a designed sampling protocol, samples from this pilot
plant were collected for analysis at two laboratories as a quality
assurance / quality control check. Results showed that Brass Canal
upstream is contaminated with dark, thick and viscous oily film with
characteristic hydrocarbon smell while downstream, thin oily film
interspersed with water was observed. Sediments were observed to be
dark with mixture of brownish sandy soil with TPH ranging from
17,800 mg/kg in Lot 1 to 88,500 mg/kg in Lot 12 samples. Brass
Canal bank soil was observed to be sandy from ground surface to 3m,
below ground surface (bgs) it was silty-sandy and brownish while
subsurface soil (4-10m bgs) was sandy-clayey and whitish/grayish
with typical hydrocarbon smell. Preliminary results obtained so far
have been very promising but were proprietary. This project is
considered, to the best of technical literature knowledge, the first
large-scale on-site bioremediation project in the Niger Delta region,
Nigeria.
Abstract: The concentrations of heavy metals in sediments of
Qua Iboe River Estuary (QIRE) were monitored at four different
sampling locations in wet and dry seasons. A preliminary survey to
determine the four sampling stations along the river continuum
showed that the area spanned between
Abstract: A chromium-loaded ash originating from incineration of tannery sludge under anoxic conditions was mixed with low grade soda-lime glass powder coming from commercial glass bottles. The relative weight proportions of ash over glass powder tested were 30/70, 40/60 and 50/50. The solid mixtures, formed in green state compacts, were sintered at the temperature range of 800o C up to 1200o C. The resulting products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDXS) and micro-indentation. The above methods were employed to characterize the various phases, microstructure and hardness of the produced materials. Thermal treatment at 800o C and 1000o C produced opaque ceramic products composed of a variety of chromium-containing and chromium-free crystalline phases. Thermal treatment at 1200o C gave rise to composite products, where only chromium-containing crystalline phases were detected. Hardness results suggest that specific products are serious candidates for structural applications.
Abstract: Rice straw is lignocellulosic biomass which can be utilized as substrate for the biogas production. However, due to the property and composition of rice straw, it is difficult to be degraded by hydrolysis enzymes. One of the pretreatment methods that modify such properties of lignocellulosic biomass is the application of lignocellulose-degrading microbial consortia. The aim of this study is to investigate the effect of microbial consortia to enhance biogas production. To select the high efficient consortium, cellulase enzymes were extracted and their activities were analyzed. The results suggested that microbial consortium culture obtained from cattle manure is the best candidate compared to decomposed wood and horse manure. A microbial consortium isolated from cattle manure was then mixed with anaerobic sludge and used as inoculum for biogas production. The optimal conditions for biogas production were investigated using response surface methodology (RSM). The tested parameters were the ratio of amount of microbial consortium isolated and amount of anaerobic sludge (MI:AS), substrate to inoculum ratio (S:I) and temperature. Here, the value of the regression coefficient R2 = 0.7661 could be explained by the model which is high to advocate the significance of the model. The highest cumulative biogas yield was 104.6 ml/g-rice straw at optimum ratio of MI:AS, ratio of S:I, and temperature of 2.5:1, 15:1 and 44°C respectively.
Abstract: Degradation of agricultural soils has increased rapidly
during the last 20 years due to the indiscriminate use of pesticides
and other anthropogenic activities. Currently, there is an urgent need
of soil restoration to increase agricultural production. Utilization of
sewage sludge or municipal solid waste is an important way to
recycle nutrient elements and improve soil quality. With these
amendments, nutrient availability in the aqueous phase might be
increased and production of healthier crops can be accomplished.
This research project aimed to achieve sustainable management of
tropical agricultural soils, specifically in Puerto Rico, through the
amendment of water treatment plant sludge’s. This practice avoids
landfill disposal of sewage sludge and at the same time results costeffective
practice for recycling solid waste residues. Coriander
sativum was cultivated in a compost-soil-sludge mixture at different
proportions. Results showed that Coriander grown in a mixture of
25% compost+50% Voladora soi+25% sludge had the best growth
and development. High chlorophyll content (33.01 ± 0.8) was
observed in Coriander plants cultivated in 25% compost+62.5%
Coloso soil+ 12.5% sludge compared to plants grown with no sludge
(32.59 ± 0.7). ICP-OES analysis showed variations in mineral
element contents (macro and micronutrients) in coriander plant
grown I soil amended with sludge and compost.
Abstract: Hybrid bioreactor having both suspended-growth and
attached-growth bacteria is found a novel and excellent bioreactor
system for treating the municipal wastewater containing inhibitory
substrates too. In this reactor a fraction of substrate is used by
suspended biomass and the remaining by attached biomass resulting
in the competition between the two growths for the substrate. The
combination of suspended and attached growth provides the system
with enhanced biomass concentration and sludge age more than those
in ASP. Similar to attached growth system, the hybrid bioreactor
ensures considerable efficiency for treating toxic and refractory
substances in wastewater. For the process design of hybrid bioreactor
a suitable mathematical model is required. Although various
mathematical models were developed on hybrid bioreactor in due
course of time in earlier research works, none of them was found
having a specific simplified solution of the corresponding models and
without having any drawback. To overcome this drawback authors
already developed a simplified mathematical model for process
design of a hybrid bioreactor. The present paper briefly highlights on
the various aspects of process design of an aerobic hybrid bioreactor
for the treatment of municipal wastewater.
Abstract: The concentrations of cadmium and lead in sewage
sludge samples were determined by Atomic Absorption
Spectrometric Method. Samples of sewage sludge were obtained
from three sewage treatment plants localised in Middle Region of
Libya (Misrata, Msallata and Tarhünah cities).
The results shows that, the mean levels of Cadmium for all regions
are ranges from 81 to 123.4 ppm and these values are higher than the
limitations for the international standard which are not registered
more than 50 ppm (dry weight) in USA, Egypt and the EU countries.
While, the lead concentrations are ranged from 8.0 to 189.2 ppm and
all values are within the standard limits which graduated between
(275–613) ppm.
Abstract: Microbial fuel cells (MFCs) represent a promising
technology for simultaneous bioelectricity generation and wastewater
treatment. Catalysts are significant portions of the cost of microbial
fuel cell cathodes. Many materials have been tested as aqueous
cathodes, but air-cathodes are needed to avoid energy demands for
water aeration. The sluggish oxygen reduction reaction (ORR) rate at
air cathode necessitates efficient electrocatalyst such as carbon
supported platinum catalyst (Pt/C) which is very costly. Manganese
oxide (MnO2) was a representative metal oxide which has been
studied as a promising alternative electrocatalyst for ORR and has
been tested in air-cathode MFCs. However the single MnO2 has poor
electric conductivity and low stability. In the present work, the MnO2
catalyst has been modified by doping Pt nanoparticle. The goal of the
work was to improve the performance of the MFC with minimum Pt
loading. MnO2 and Pt nanoparticles were prepared by hydrothermal
and sol gel methods, respectively. Wet impregnation method was
used to synthesize Pt/MnO2 catalyst. The catalysts were further used
as cathode catalysts in air-cathode cubic MFCs, in which anaerobic
sludge was inoculated as biocatalysts and palm oil mill effluent
(POME) was used as the substrate in the anode chamber. The asprepared
Pt/MnO2 was characterized comprehensively through field
emission scanning electron microscope (FESEM), X-Ray diffraction
(XRD), X-ray photoelectron spectroscopy (XPS), and cyclic
voltammetry (CV) where its surface morphology, crystallinity,
oxidation state and electrochemical activity were examined,
respectively. XPS revealed Mn (IV) oxidation state and Pt (0)
nanoparticle metal, indicating the presence of MnO2 and Pt.
Morphology of Pt/MnO2 observed from FESEM shows that the
doping of Pt did not cause change in needle-like shape of MnO2
which provides large contacting surface area. The electrochemical
active area of the Pt/MnO2 catalysts has been increased from 276 to
617 m2/g with the increase in Pt loading from 0.2 to 0.8 wt%. The
CV results in O2 saturated neutral Na2SO4 solution showed that
MnO2 and Pt/MnO2 catalysts could catalyze ORR with different
catalytic activities. MFC with Pt/MnO2 (0.4 wt% Pt) as air cathode
catalyst generates a maximum power density of 165 mW/m3, which
is higher than that of MFC with MnO2 catalyst (95 mW/m3). The
open circuit voltage (OCV) of the MFC operated with MnO2 cathode
gradually decreased during 14 days of operation, whereas the MFC
with Pt/MnO2 cathode remained almost constant throughout the
operation suggesting the higher stability of the Pt/MnO2 catalyst.
Therefore, Pt/MnO2 with 0.4 wt% Pt successfully demonstrated as an
efficient and low cost electrocatalyst for ORR in air cathode MFC with higher electrochemical activity, stability and hence enhanced
performance.
Abstract: In recent decades with the development of technology
and lack of food sources, sewage sludge in production of human
foods is inevitable. Various sources of municipal and industrial
sewage sludge that is produced can provide the requirement of plant
nutrients. Soils in arid, semi-arid climate of central Iran that most
affected by water drainage, iron and zinc deficiencies, using of
sewage sludge is helpful. Therefore, the aim of this study is
investigation of sewage sludge and manure application on Ni, Pb and
Cd uptake by Savory. An experiment in a randomized complete block
design with three replications was performed. Sewage sludge
treatments consisted of four levels, control, 15, 30, 80 tons per
hectares; the manure was used in four levels of control, 20, 40 and 80
tons per hectare. Results showed that the wet and dry weights was not
affected by sewage sludge using, while, manure has significant effect
on them. The effect of sewage sludge on the cadmium and lead
concentrations were significant. Interactions of sewage sludge and
manure on dry weight values were not significant. Compare mean
analysis showed that increasing the amount of sewage sludge had no
significant effect on cadmium concentration and it reduced when
sewage sludge usage increased. This is probably due to increased
plant growth and reduced concentrations of these elements in the
plant.
Abstract: Biological conversion of biomass to methane has
received increasing attention in recent years. Grasses have been
explored for their potential anaerobic digestion to methane. In this
review, extensive literature data have been tabulated and classified.
The influences of several parameters on the potential of these
feedstocks to produce methane are presented. Lignocellulosic
biomass represents a mostly unused source for biogas and ethanol
production. Many factors, including lignin content, crystallinity of
cellulose, and particle size, limit the digestibility of the hemicellulose
and cellulose present in the lignocellulosic biomass. Pretreatments
have used to improve the digestibility of the lignocellulosic biomass.
Each pretreatment has its own effects on cellulose, hemicellulose and
lignin, the three main components of lignocellulosic biomass. Solidstate
anaerobic digestion (SS-AD) generally occurs at solid
concentrations higher than 15%. In contrast, liquid anaerobic
digestion (AD) handles feedstocks with solid concentrations between
0.5% and 15%. Animal manure, sewage sludge, and food waste are
generally treated by liquid AD, while organic fractions of municipal
solid waste (OFMSW) and lignocellulosic biomass such as crop
residues and energy crops can be processed through SS-AD. An
increase in operating temperature can improve both the biogas yield
and the production efficiency, other practices such as using AD
digestate or leachate as an inoculant or decreasing the solid content
may increase biogas yield but have negative impact on production
efficiency. Focus is placed on substrate pretreatment in anaerobic
digestion (AD) as a means of increasing biogas yields using today’s
diversified substrate sources.
Abstract: Local utilities often face problems of local industrial
wastes, storm water disposal due to existing strict regulations. For
many local industries, the problem of wastewater treatment and
discharge into surface reservoirs can’t be solved through the use of
conventional biological treatment techniques. Current discharge
standards require very strict removal of a number of impurities such
as ammonia, nitrates, phosphate, etc. To reach this level of removal,
expensive reagents and sorbents are used.
The modern concept of rational water resources management
requires the development of new efficient techniques that provide
wastewater treatment and reuse.
As RO membranes simultaneously reject all dissolved impurities
such as BOD, TDS, ammonia, phosphates etc., they become very
attractive for the direct treatment of wastewater without biological
stage. To treat wastewater, specially designed membrane "open
channel" modules are used that do not possess "dead areas" that cause
fouling or require pretreatment. A solution to RO concentrate
disposal problem is presented that consists of reducing of initial
wastewater volume by 100 times. Concentrate is withdrawn from
membrane unit as sludge moisture. The efficient use of membrane
RO techniques is connected with a salt balance in water system.
Thus, to provide high ecological efficiency of developed techniques,
all components of water supply and wastewater discharge systems
should be accounted for.
Abstract: Despite of few research works on municipal sludge, still there is a lack of actual data. Thus, this work was focused on the conditioning and rheology of fresh activated sludge. The effect of cationic polyelectrolyte has been investigated at different concentrations and pH values in a comparative fashion. Yield stress is presented in all results indicating the minimum stress that necessary to reach flow conditions. Connections between particle-particle is the reason for this yield stress, also, the addition of polyelectrolyte causes strong bonds between particles and water resulting in the aggregation of particles which required higher shear stress in order to flow. The results from the experiments indicate that the cationic polyelectrolytes have significant effluence on the sludge characteristic and water quality such as turbidity, SVI, zone settling rate and shear stress.
Abstract: Numerous amounts of metallurgical dusts and sludge containing iron as well as some other valuable elements such as Zn, Pb and C are annually produced in the steelmaking industry. These alternative iron ore resources (fines) with unsatisfying physical and metallurgical properties are difficult to recycle. However, agglomerating these fines to be further used as a feed stock for existing iron and steelmaking processes is practiced successfully at several plants but for limited extent.
In the present study, briquettes of integrated steelmaking industry waste materials (namely, BF-dust and sludge, BOF-dust and sludge) were used as feed stock to produce direct reduced iron (DRI). Physical and metallurgical properties of produced briquettes were investigated by means of TGA/DTA/QMS in combination with XRD. Swelling, softening and melting behavior were also studied using heating microscope.