Treatment of Compost Leachate by Membrane Processes

DESALINATION AND WATER TREATMENT, 2021

The Oum Azza Landfill, which is located in the suburb of Rabat, receives daily 2,500-2,800 t of solid waste and produces 660 m 3 /d of landfill leachate. The leachate treatment plant of Oum Azza includes a biological pretreatment (aeration tank and anoxic tank followed by a bag filter), and a membrane processes by reverse osmosis (RO). A low RO recovery rate and frequent stops caused by membranes fouling have been observed, this behavior is mainly due to the poor quality of the effluent after pretreatment. To address this problem and improve the physico-chemical quality of the effluent upstream of the RO processes, we consider in this paper the feasibility of ultrafiltration (UF) separation as a pretreatment. The purpose of this study is to evaluate and compare the performance of three ceramic UF membranes with different pore sizes (0.02, 0.05 and 0.1 µm). The transmembrane pressure (TMP) and circulation velocity effect on the quantity and the quality of permeate and on the removal efficiency of chemical oxygen demand (COD) and suspended solid (SS) are performed. The pretreatment of the leachate by UF shows that the SS and COD retention increase with TMP for all the tested membranes and reach, for a circulation velocity of 0.5 m/s, the maximum values of 85%, 77% and 72% respectively for COD and 70.4%, 62% and 55% for SS. On the other hand, the study shows that circulation velocity has no influence on the physico-chemical quality of the permeate in the range of the applied TMP. However, for an applied TMP, the flow rate increases with the circulation velocity. The results obtained show a clear improvement in effluent quality compared to the conventional pretreatment used in the leachate treatment plant of Oum Azza but pollutants indicators contents are still high and the effluent cannot be directed to the RO unit. Three methods are proposed to perfect the quality of the effluent at the entrance of the RO unit.

Journal of Hazardous Materials, 2013

The fate of organics and nitrogen during the biological treatment with MBR and subsequent membrane filtration processes (Nano Filtration, NF; Reverse Osmosis, RO) were investigated for a landfill leachate. The Chemical Oxygen Demand (COD) and Total Kjeldahl Nitrogen (TKN) removal performances of Membrane Bioreactor (MBR) were obtained to be around 89% and 85%, respectively. The effluent COD of MBR was measured to be 1935 mg/L (30 kDa) which is much lower than experimentally determined soluble inert COD of 3200 mg/L using 0.45 µm filter. The readily and slowly biodegradable COD fractions were estimated to be 17% and 52% of raw influent COD, respectively. The respirometry based modeling test performed on raw leachate exhibited much slower degradation kinetics compared to municipal wastewater. A unique subset of model parameters was extracted from batch respirometry by using acclimated MBR sludge. The sequential Ultrafiltration (UF) experiments (Particle Size Distribution, PSD) revealed that most of torganics was below 2 nm filter mesh size. In addition, NF/RO post treatment after MBR system was required to increase COD and Total Nitrogen (TN) removal performances up to 99%. Relatively lower salt rejection rates around 94% was obtained for RO system as a post treatment of MBR system.

Membranes

This paper presents a case study describing a full-scale membrane bioreactor (MBR) for the pretreatment of landfill leachates. The treatment train includes an aerated equalization tank, a denitrification tank, an oxidation/nitrification tank, and two ultrafiltration units. The plant has worked continuously since 2008 treating landfill leachates at a flux of 2–11 L·h−1·m−2. The old train of membranes worked in these conditions for more than seven years prior to being damaged and replaced. The permeability (K) of the membrane varied between 30 and 80 L·h−1·m−2·bar−1 during the years of operation. In 2010, after two years of operation, the oxidation/nitrification tank was changed to work in alternate cycles of aerated and anoxic conditions, in order to improve the denitrification process. The MBR, working at a mean sludge retention time of 144 days and with mixed liquor suspended solids of 17 g/L, achieved high removal rates of conventional contaminants, with more than 98% for Biochemi...

Leachate contains high concentration of organic matter, color, heavy metals, and toxic substances. In the past few decades, leachate treatment process was adopted from conventional method such as biological methods as aerobic, anaerobic and anoxic, and physical and chemical methods as air stripping, coagulation and membrane filtration. Previous study on leachate treatment by conventional method indicated that advance development of technology is desirable. To ensure the environment can sustain with the development, a few remedial actions were considered. One of them is membrane separation technology. Membranes encompass a wide range of applications in fluid separation and now considered new emerging separation technology and shows increasingly attractiveness for treatment of leachate. Although this technology emerged a long time ago, technical viability has only occurred over the last 30 years. Due to successes, membrane separation becomes a promising as an alternative treatment technology and competing with the conventional system techniques. Implementing membrane separation can be a solution to reduce impact of environmental pollution and improve quality of effluent. The applications in leachate treatment require the development of new membranes and processes. This paper reviews the potential implementation of an innovative membrane for leachate treatment.

Sanitary landfilling is nowadays the most common way to eliminate municipal solid wastes, although waste management hierarchy considers landfilling as a last option. The resultant leachate produced due to waste transformation and rainfall can be identified by specific characteristics and variables, corresponding to high-strength wastewaters, which generate impacts and risks in the environment. This situation imposes stringently leachate treatment by appropriate and efficient methods and processes. This research analyzes the performance of a municipal waste landfill leachate treatment system applying a membrane processreverse osmosis (RO), for almost a year of operation. The system equipped with disc-tube (DT) membrane modules, and located in the sanitary landfill of the city of Iasi, Romania includes two stages: LEACHATE stage and PERMEATE stage, preceded by a pre-treatment module consisting of sand and cartridge filters. A storage system is included in the flow-sheet, for cleaning agents and various chemicals. Pumping stations provide the necessary operating pressure in the system. A removal efficiency of contaminants (COD, NH 4 + , electrical conductivity etc.) exceeding 90% was achieved. Any variation in permeate flux (14-22 L/m 2 h) and separation efficiency (94-100%) was due to increasing osmotic pressure and fouling, scaling and polarization of concentration. The RO process demonstrated a high rejection rate for both organic and inorganic contaminants dissolved in the leachate, together with a high flexibility alongside the changes in the leachate composition, depending on pressure, temperature, pH feeding flow rate of leachate.

Journal of Hazardous Materials, 2009

This study presents a configuration for the complete treatment of landfill leachate with high organic and ammonium concentrations. Ammonia stripping is performed to overcome the ammonia toxicity to aerobic microorganisms. By coagulation-flocculation process, COD and suspended solids (SS) were removed 36 and 46%, respectively. After pretreatment, an aerobic/anoxic membrane bioreactor (Aer/An MBR) accomplished the COD and total inorganic nitrogen (total-N i ) removals above 90 and 92%, respectively, at SRT of 30 days. Concentrations of COD and total-N i (not considering organic nitrogen) in the Aer/An MBR effluent decreased to 450 and 40 mg/l, respectively, by significant organic oxidation and nitrification/denitrification processes. As an advanced treatment for the leachate, the reverse osmosis (RO) was applied to the collected Aer/An MBR effluents. Reverse osmosis provided high quality effluent by reducing the effluent COD from MBR to less than 4.0 mg/l at SRT of 30 days.

Desalination, 2012

Landfill leachate (LFL), especially old LFL, is very difficult to treat using conventional biological processes. To this end, membrane bioreactor (MBR) has proven to be a promising alternative. The membrane separation capacity of a MBR allows the retention of most microbial cells in the reactor to maintain a high biomass concentration, resulting in an efficient biological digestion system. As a result, excellent biological oxygen demand (BOD) and ammonia removals of 90% or higher are achievable with a much shorter hydraulic residence time (HRT) and much larger organic loading rate (OLR) in comparison to conventional biological systems. MBR also allows excellent chemical oxygen demand (COD) removal (75% or higher), even with old LFL under optimized conditions. MBRs have also been demonstrated to be effective in the removal of micropollutants. Furthermore, recent developments such as anaerobic MBR and PAC (powdered activated carbon)-amended MBR have shown great potentials in LFL treatment. MBRs can provide stable performance while accommodating large variations in composition of influents and other operation conditions. However, short HRT and high ammonia concentration were found to have adverse effects. Extremely long solids residence time was also found to lower MBR performance.

Water Research, 1999

ÐThis paper deals with an experimental study describing the treatment of land®ll leachate by means of a pilot-scale reverse osmosis unit. Leachate streams with a CO parameter in the range of 0± 1749 mg l À1 have been adopted. The¯ux rate of the permeate through the membrane decreased linearly with the COD factor. The rejection coecient of COD was practically independent of the COD value, but was signi®cantly aected by the applied pressure. By operating at 53 atm, COD rejection values around 98% were obtained. Finally, the eect of COD on the separation of some heavy metals was investigated. For most metals this in¯uence was negligible. Only the rejection coecient of Zn decreased signi®cantly upon increasing the COD of the leachate stream.

Journal of environmental management, 2016

Combination of high performance membrane bioreactor (MBR) equipped with ultrafiltration and electro-oxidation process (EOP) by boron-doped diamond electrode (BDD) was used to effectively treat highly contaminated old landfill leachate. MBR and EOP were optimized for raw and pretreated landfill leachate. Seasonal changes dramatically affected the both processes' performance, as the landfill leachate was ¾ more concentrated in winter. For MBR, organic load rate of 1.2 gCOD/L/day and sludge retention time of 80 days was considered as the optimum operating condition in which COD, TOC, NH4(+) and phosphorous removal efficiencies reached the average of 63, 35, 98 and 52%, respectively. The best performance of EOP was in current intensity of 3 A with treatment of time of 120 min. Effluent of electro-oxidation was more toxic due to the presence of radicals and organochlorinated compounds. These compounds were removed by stripping or assimilation of sludge if EOP was used as a pretreatme...