Viability of a Single-Stage Unsaturated-Saturated Granular Activated Carbon Biofilter for Greywater Treatment

Compared with conventionally collected sewage, source-diverted greywater has a higher potential for on-site treatment and reuse due to its lower contaminant levels and large volume. A new design of granular activated carbon (GAC) biofilters was developed by incorporating unsaturated and saturated zones in a single stage to introduce an efficient, passive, and easy-to-operate technology for greywater on-site treatment at the household scale. The design was customized for its intended application considering various aspects including the reactor’s configuration, packing media, and feeding strategy. With the highest hydraulic and organic loadings of 1.2 m3 m−2 d−1 and 3.5 kg COD m−2 d−1, respectively, and the shortest retention time of 2.4 h, the system maintained an average total chemical oxygen demand removal rate of 94% with almost complete removal of nutrients throughout its 253 days of operation. The system showed a range of reduction efficacy towards five surrogates representing viruses, bacteria, and Cryptosporidium and Giardia (oo)cysts. A well-functioning biofilm was successfully developed, and its mass and activity increased over time with the highest values observed at the top layers. The key microbes within the biofilter were revealed. Feasibility of the proposed technology was investigated, and implications for design and operation were discussed.

Application of composite degradable modified starch-based flocculant on dewatering and recycling properties

Sludge dewatering is an important step for wastewater treatment. Composite degradable flocculant (CDF) was prepared by cationic polyacrylamide (PAM) grafting onto modified starch with a novel initiator, and characterized by Fourier transform infrared spectroscopy. The microstructure of flocculated sludge was characterized by scanning electron microscopy. The study investigated the properties of CDF compared to PAM, which showed that the prepared CDF exhibited a highly effective flocculation on sludge dewatering, a higher transmittance and chemical oxygen demand removal rate, and a lower value of effluent ammonia nitrogen and total phosphorus. The fermentation process was also analyzed by testing the performance of dewatered sludge (temperature, pH, ammonia nitrogen, E4/E6 (humic acid absorbance at 465 nm (E4) and 665 nm (E6))). The dehydrated sludge with CDF could be easily compressed into cakes by belt-filter for easy transportation and storage. With the continuous addition of CDF and PAM, the corresponding index of capillary suction time (CST) increased. Moreover, the total value of CST with CDF was low, showing a good dewaterability. In addition, the sludge index of pumping time and moisture content with CDF were low in contrast with PAM. Fermentation experiments demonstrated that sludge with CDF had a comparatively high temperature and low value of E4/E6. Such novel CDF shows enormous potential in wastewater treatment and sludge fermentation.

Assessment of Anaerobic Co-Digestion Effects of Maize Cob and Poultry Manure on Biogas Yields and Their Digestate Characteristics

Aim: The aim of the study was to assess the effects of anaerobic co-digestion of maize cob and poultry manure on biogas yields and their digestate characteristics. Place and Duration of Study: Department of Forestry Technology, Federal College of Forestry, Jos between March and April, 2018. Methodology: Slurries of five co-substrate treatment ratios viz 0:1(T1), 1:3(T2), 1:1(T3), 3:1(T4) and 1:0(T5) of these wastes (in three replicates) were separately fed to 13.6L locally made batch-digesters. The anaerobic reactors were monitored for a 56 day retention period. Weekly biogas yields and some digestate characteristics were measured by standard methods. Results: The cumulative biogas yields was in the order of T3(2481.3 mL/kg) >TI(2197.9 mL/kg) > T4(2163.0 mL/kg) > T2(2116.3 mL/kg) >T5(1713.2 mL/kg), in favor of the mixed substrates. While the percentage C:N reductions ranged from (12.94% - 81.80%), with T5 and T1 recording the highest and lowest values respectively. The chemical oxygen demand removal was in the order of T3(80.70%) > T4(58.00%) >T5(46.81%) >T1(34.15%) >T2(13.16%). The anaerobic digestion (AD) effected reductions in Mg, C, Ca, P, Mn, Zn, Fe, Pb and increase in Cu contents of the digestates across treatments. While the K contents increased in T2(36.72%), T3(229.79%) and T4(220.51%); %N in T3(9.94%), T4(113.19%) and T5(291.84%) and Na increased only in T4(4.55%). The Cu contents indicated % increase in the order of T5(487.5%) >T3(270.97%) >T2(268.10%) >T4(43.66%) >T1(35.82%). Conclusion: The anaerobic co-digestion of these organic wastes had unlocked the alternative energy potentials, enhanced the bioremediation tendency, while promoting sustainable public health and environmental management.

Photo-Fenton Degradation of RB5 Dye in Aqueous Solution Using Fe Supported on Mexican Natural Zeolite

A Mexican natural zeolite (MNZ) was impregnated with Fe at concentrations of 5 and 10 mg FeCl3/g MNZ (MNZ/Fe) in order to study the photo-Fenton degradation of Reactive Black 5 (RB5) dye. Two samples were prepared and calcined at 550 and 700°C for each concentration. These samples were also characterized by the following techniques: X-ray diffraction (XRD) to determine crystalline phases of mineral, X-ray photoelectron spectroscopy (XPS) to observe the elemental composition of the material where the main element was Fe as Fe2p, Mössbauer to establish the phases in the material which were magnetite (Fe3O4), fayalite, and chlorite, Raman to corroborate that magnetite clusters in natural material were presented, and transmission electron microscopy (TEM) by which magnetite nanoparticles were observe on zeolite surface. Afterwards, the catalytic degradation of RB5 dye was performed by photo-Fenton process using a 2.2 W lamp as a radiation source. Four initial concentrations of RB5 dye ((RB5)0) were evaluated which ranged from 40 to 100 mg/L. Then, the evaluation reaction was carried out by UV-Vis spectroscopy to know the change in RB5 concentration and chemical oxygen demand (COD) removal to determine the organic carbon. The best results on the photo-Fenton degradation was 91% discoloration and 68.5% chemical oxygen demand removal based on an initial concentration RB50=100 mg/L and 10 mg MNZ/Fe (700°C of calcined temperature) at MNZ/Fe=0.05 g/L catalyst dose in aqueous solution, H2O2=3 g/L, pH=2.5, and 180 minutes of reaction time. Subsequently, variations on (RB5)0, pH, (H2O2), and (MNZ/Fe) were assessed in order to optimize the process by keeping 10 MNZ/Fe. The optimal RB5 dye degradation was achieved at RB50=100 mg/L in the presence of MNZ/Fe=0.2 g/L, H2O2=3 g/L and pH=2.5 where the highest discoloration and chemical oxygen demand removal were 93 and 70.5 at 180 min. Finally, the kinetic reaction was evaluated as a pseudo-first-order kinetics with an apparent rate constant (kapp) of 0.0225 min-1 at latest conditions.