Measuring organic carbon, nutrients and heavy metals in rivers receiving leachate from controlled and uncontrolled municipal solid waste landfills

Since landfilling is the common method of waste disposal in Malaysia, river water is greatly exposed to the risk of contamination from leachate unless proper leachate management is carried out. In this study, leachates from three different types of landfills, namely active uncontrolled, active controlled and closed controlled, were characterized, and their relationships with river water chemistry were examined monthly for a year. The influence of leachate on river water chemistry from each type of landfill depended on many factors, including the presence of a leachate control mechanism, leachate characteristics, precipitation, surface runoff and the applied treatment. The impact of leachate from an active uncontrolled landfill was the highest, as the organic content, NH(4)(+)-N, Cd and Mn levels appeared high in the river. At the same time, influences of leachate were also observed from both types of controlled landfills in the form of inorganic nitrogen (NH(4)(+)-N, NO(3)(-)-N and NO(2)(-)-N) and heavy metals (Fe, Cr, Ni and Mn). Improper treatment practice led to high levels of some contaminants in the stream near the closed controlled landfill. Meanwhile, the active controlled landfill, which was located near the coastline, was exposed to the risk of contamination resulting from the pyrite oxidation of the surrounding area

Production of biochar with high mineral content from oil palm biomass

Carbonization of oil palm empty fruit bunch (OPEFB) biomass for the production of high mineral content biochar under an uncontrolled carbonization temperature and controlled air flow rate was studied using a pilot-scale brick carbonization reactor. The maximum temperature during the carbonization process was found to be in the range of 543 to 564 oC at exhaust gas flow rate of 36 m3/hr. All minerals (i.e P, K ,Mg, Ca, Na, Mn, Fe, Cr, AI) showed an increased from the feedstock concentration up to 300 %. The concentration of heavy metal extracted from OPEFB biochar was lower than listed ceiling permitted levels. This proposed system without electrical control and heating source is preferable to the industry due to its simplicity, ease of operation and low energy requirement making it suitable for OPEFB biochar production for mulching purposes with more than double the mineral content compared to raw OPEFB biomass

Comparison of Cap and QAM-DMT Modulation Format for In-Home Network Environment

Carrierless amplitude phase (CAP) modulation format has appeared as a potential advanced modulation format candidate for spectrally efficient single-carrier modulation type due to less complexity and has competitive performance. In this paper, the comparison between 2D-CAP-4 and 4-QAM-DMT modulation format over 3 km single mode fiber (SMF) transmission link using 1310 nm vertical cavity surface emitting laser (VCSEL) has been performed for inhome network environment. The net bit rates of 625 Mb/s and 454.6 Mb/s are achieved for 2D-CAP-4 and 4-QAM-DMT, respectively. Spectral efficiencies of 1.89 b/s/Hz for 2D-CAP-4 and 1.43 b/s/Hz for 4-QAM-DMT are reported. It is observed that 2D-CAP-4 outperforms 4-QAM-DMT with 1.14 dB better receiver sensitivity. These results indicate that the privilege properties of CAP modulation format can be an attractive prospect for in-home network environment

Nitrification of ammonium-rich sanitary landfill leachate

The nitrification of ammonium-rich wastewater is considered challenging due to the substrate inhibition particularly in the form of free ammonia (FA) and free nitrous acid (FNA) in ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB). The feasibility of the nitrifying activated sludge system to completely nitrify synthetic stabilized landfill leachate with concentration of 1452 mg/L was tested in this study. The process started with 0.4 kg /m3/day of nitrogen loading rate (NLR) in a fed-batch mode to avoid any accumulation of the FA and FNA in the system followed by increasing the nitrogen loading rate (NLR) gradually. Complete nitrification was achieved with a very high ammonium removal percentage (100%). The maximum specific and volumetric nitrification rate obtained were 0.49 g /g VSS/day and 3.0 kg /m3/day, respectively which were higher than those reported previously for ammonium-rich removal using activated sludge system. The nitrifying sludge exhibited good settling characteristics of up to 36 mL/g VSS and a long SRT of more than 53 days which contributed to the success of the nitrification process. The coexistence and syntrophic association of the AOB and NOB was observed by using Fluorescence in situ hybridization (FISH) technique which supported the results on complete nitrification obtained in the system. These findings would be of prominent importance for further treatment of actual sanitary landfill leachate

Nitrification of high-strength ammonium landfill leachate with microbial community analysis using (FISH).

Nitrification of mature sanitary landfill leachate with high-strength of N_NHþ 4 (1080–2350mg L_1) was performed in a 10 L continuous nitrification activated sludge reactor. The nitrification system was acclimatized with synthetic leachate during feed batch operation to avoid substrate inhibition before being fed with actual mature leachate. Successful nitrification was achieved with an approximately complete ammonium removal (99%) and 96% of N_NHþ 4 conversion to N_NO_3 . The maximum volumetric and specific nitrification rates obtained were 2.56 kg N_NHþ4 m_3 day_1 and 0.23 g N_NHþ4g_1 volatile suspended solid (VSS) day_1, respectively, at hydraulic retention time (HRT) of 12.7 h and solid retention time of 50 days. Incomplete nitrification was encountered when operating at a higher nitrogen loading rate of 3.14 kg N_NHþ 4 m_3 day_1. The substrate overloading and nitrifiers competition with heterotrophs were believed to trigger the incomplete nitrification. Fluorescence in situ hybridization (FISH) results supported the syntrophic association between the ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria. FISH results also revealed the heterotrophs as the dominant and disintegration of some AOB cell aggregates into single cells which further supported the incomplete nitrification phenomenon

Carbon monoxide reduction in the flue gas during biochar production from oil palm empty fruit bunch

Biomass carbonization technology is implemented to produce charcoal with high-calorific content. However, this technology releases pollutant gases, which adversely affect ambient environment and human health. This study proposed a catalytic gas treatment method using platinum-supported alumina catalyst (Pt/γ-Al2O3) for carbon monoxide emission reduction in oil palm empty fruit bunch carbonization. Carbonization released a rather high carbon monoxide concentration of 5558 ± 53 mg m−3 in the flue gas, exceeding the permissible limit of 1000 mg m−3. At 2.5 wt% of catalyst dosage, the carbon monoxide emission substantially was reduced to 595 ± 9 mg m−3, achieving 89.3% carbon monoxide removal efficiency. This was due to oxidation by the platinum-supported alumina catalyst (Pt/γ-Al2O3), which was done at low temperature, thus transforming carbon monoxide into carbon dioxide. The catalyst demonstrated reusability, attaining >80% carbon monoxide removal efficiency for 5 consecutive carbonization cycles. The biochar produced contained a high energy content of 24.6 ± 0.7 MJ kg−1, which was suitable to be used as a coal substitute

A holistic treatment system for palm oil mill effluent by incorporating the anaerobic-aerobic-wetland sequential system and a convective sludge dryer

An integrated treatment system which incorporated an anaerobic-aerobic-wetland sequential system (AAWSS) and a convective sludge dryer (CSD) was established to treat highly polluting palm oil mill effluent (POME) in a shorter retention period and with a smaller area requirement. Before actual treatment, a start-up operation was performed to achieve optimal degradation performance. The strategy involved a stepwise feeding from 0.2 to 1 m3 d−1 at three day intervals for 15 days. During the operation, the lowest hydraulic retention time of 21 days was achieved and the biogas production was gradually increased from 1442 to 11,028 kg d−1with the increase of organic loads from 0.46 to 2.2 kg m−3 d−1. COD, VSS and VFA were almost completely (99%) removed, whereas the average percentage removals of SS and TN were 96% and 72%, respectively. To demonstrate the plant’s robustness in treating POME, the AAWSS was proceeded with a 360 days operation. A slight deterioration in COD and SS removals were observed from day 225 to day 265 due to an organic shock load. One unanticipated finding was that the AAWSS regained its stability shortly thereafter thus ensuring consistency of the treatment performance for long-term use. Further treatment with CSD was designed to produce a clear effluent that surpassed the industrial effluent discharge limits at low-cost. By referring to mass balance, the production efficiency achieved 95% condensate yield, leaving 7% concentrate and 2% dewatered solids as byproducts

A one-step self-sustained low temperature carbonization of coconut shell biomass produced a high specific surface area biochar-derived nano-adsorbent

A one-step self-sustained carbonization of coconut shell biomass, carried out in a brick reactor at a relatively low temperature of 300–500°C, successfully produced a biochar-derived adsorbent with 308 m2/g surface area, 2 nm pore diameter, and 0.15 cm3/g total pore volume. The coconut shell biochar qualifies as a nano-adsorbent, supported by scanning electron microscope images, which showed well-developed nano-pores on the surface of the biochar structure, even though there was no separate activation process. This is the first report whereby coconut shell can be converted to biochar-derived nano-adsorbent at a low carbonization temperature, without the need of the activation process. This is superior to previous reports on biochar produced from oil palm empty fruit bunch

Successful scaling-up of self-sustained pyrolysis of oil palm biomass under pool-type reactor

An appropriate technology for waste utilisation, especially for a large amount of abundant pressed-shredded oil palm empty fruit bunch (OFEFB), is important for the oil palm industry. Self-sustained pyrolysis, whereby oil palm biomass was combusted by itself to provide the heat for pyrolysis without an electrical heater, is more preferable owing to its simplicity, ease of operation and low energy requirement. In this study, biochar production under self-sustained pyrolysis of oil palm biomass in the form of oil palm empty fruit bunch was tested in a 3-t large-scale pool-type reactor. During the pyrolysis process, the biomass was loaded layer by layer when the smoke appeared on the top, to minimise the entrance of oxygen. This method had significantly increased the yield of biochar. In our previous report, we have tested on a 30-kg pilot-scale capacity under self-sustained pyrolysis and found that the higher heating value (HHV) obtained was 22.6–24.7 MJ kg−1 with a 23.5%−25.0% yield. In this scaled-up study, a 3-t large-scale procedure produced HHV of 22.0–24.3 MJ kg−1 with a 30%−34% yield based on a wet-weight basis. The maximum self-sustained pyrolysis temperature for the large-scale procedure can reach between 600 °C and 700 °C. We concluded that large-scale biochar production under self-sustained pyrolysis was successfully conducted owing to the comparable biochar produced, compared with medium-scale and other studies with an electrical heating element, making it an appropriate technology for waste utilisation, particularly for the oil palm industry

Simulation study on enhancing hydrogen production in an ocean thermal energy (OTEC) system utilizing a solar collector

This article reports the simulation study on the performance of utilizing a solar collector at the inlet of an evaporator to provide auxiliary heat into a system for hydrogen generation in an OTEC cycle. The conventional method of OTEC is simulated by FORTRAN programming and the results were compared with the presence of solar collector on the system. In the simulation experimental, the incoming temperature of warm seawater was boosted by using a flat plate solar collector. For the purpose of the experiment, a 100 kW OTEC cycle that was designed incorporated a solar boosting capability. Its thermodynamic efficiency was then compared through a series of simulation involving several control parameters. The results reveal that the proposed solar boosted OTEC enhanced the thermal efficiency, TE. Increase in solar power absorption can increase the net power output, thus increasing the amount of hydrogen produced. The results obtained provided insights, from a thermodynamic perspective, on the outcome of combining sustainable energy with solar thermal energy to improve the system performance