The potential of sewage sludge-derived biochar and humus mixtures for attenuation of polycyclic aromatic hydrocarbons (PAHs) in crude oil contaminated soil was evaluated. Laboratory-scale experiments involving ultisol samples spiked with crude oil, sewage sludge-derived biochar, and mixed biochar with humus sediment were monitored for removal of PAHs at the intervals of 1, 6, and 12 months. The results revealed that out of the three biochar products obtained at different pyrolysis temperatures: 500, 700, and 900 °C (designated BC500, BC700, and BC900, respectively), BC700 recorded desirable properties and acceptable levels of PAHs suitable for soil amendment. Characterisation of the mixture for functional groups using Fourier transform infrared spectroscopy (FTIR) and surface morphology using scanning electron microscopy (SEM) revealed the presence of oxygenated and nitrogenated species that could support mineralisation of PAHs, increased surface area as well as pores to aid pollutant adsorption. The study revealed that the derived mixture demonstrated the potential to reduce the level of PAHs in contaminated soil. About 70% maximum reduction in the levels of total PAHs was recorded within 1 month for soil treated with the derived mixture in comparison to the control experiment.

The biofertilizer quality of anaerobically codigested agroindustrial residues from brewer's spent grain and palm oil mill effluent was evaluated after supplementation with different livestock manure in order to validate its use as organic fertilizer. Manure supplementation assay was performed using different animal manure-inoculum to demonstrate the influence of inoculum-type on the nutrient status, plant growth promoting bacteria (PGPB) and other plant growth promoting attributes of the resultant digestate. In addition to elevated nutrient levels (K > P > Ca > Mg > S > N), the plethora of essential microbial groups (phosphate solubilizers > diazotrophs > auxin producers) that enhance nutrition and promote plant growth was evinced in the supplemented digestate compared to the control. On the other hand, environmental risk assessment revealed a notable yet inadequate reduction in indicator bacteria and putative pathogens (> 3.0 log CFU mL − 1) with potentially toxic elements within publicly available requirements. The preponderance of PGPB with excellent biofertilizing attributes observed in this study could be leveraged upon by plants thus substantiating its potential for use as organic fertilizer. However, the presence of pathogens highlights the importance of post-treatment hygienization to eliminate its biosafety risk.

The spread of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli has increased in different environments. This study aimed to evaluate the patterns of antibiotic resistance and ESBL genes among E. coli isolates collected from wastewater and recipient surface water in South Africa. Fifteen samples containing nine wastewater and six river water samples were collected from a local wastewater treatment plant. The E. coli isolates were detected using standard microbiology methods. Antibiotic susceptibility testing was performed using disc diffusion agar. The occurrence of bla CTX-M , bla SHV and bla TEM ESBL genes was investigated by PCR. Exactly 140 isolates were selected from the primary enumeration plates with a log 10 CFU/mL count that ranged from 4.1 to 4.2 (influent), 4.2 to 4.5 (biofilter) and 2.5 to 3.3 (effluent). The wastewater effluent showed an impact on the receiving water environment, as the treatment efficiency was 92% and the downstream log 10 CFU/mL count (range, 3.6–3.8 log 10 CFU/mL) was higher than the upstream count (range, 3.3–3.6 log 10 CFU/mL). Antibiotic testing results showed that 40% to 100% of E. coli isolates were resistant to ampicillin, penicillin, tetracycline and cefotaxime but susceptible to imipenem, meropenem and ciprofloxacin. A total of 40 studied isolates (28.6%) had both the bla TEM and bla CTX-M genes, while no bla SHV was detected. The wastewater treatment plants contributed multidrug-resistant ESBL-producing E. coli isolates that can be potential environmental health risks. Regular monitoring policies are recommended to prevent the spread of antibiotic resistance in the region.

The effect of different inocula on the anaerobic co-digestion of palm oil mill effluent (POME) and brewery spent grain (BSG) was evaluated for biogas production using laboratory scale bioreactors. The reactors (A: POME + BSG + cow dung, B: POME + BSG + swine dung, C: POME + BSG + swine dung + cow dung) were incubated at 35 ± 2°C for 30 days. The average biogas volume measured periodically by water displacement technique were 4.73, 38.64, and 36.45 mL gVS⁻¹ in reactors A, B and C respectively. The results indicated that reactor B produced 8.17 times more biogas than A and 1.06 times than C, whereas reactor C produced 7.71 times more gas than A, with significant differences at p = 0.

Laboratory-scale bioreactors were used to co-digest spent coconut copra (SCC) and cow urine (CU) as a co-substrate (SCC + CU) in a batch mode under thermophilic condition (45 ± 2°C) in order to enhance biogas production. The effect of CU pretreatment on the performance indicators (biogas and biomethane yields, total solids (TS), and volatile solids (VS) reduction, pH and volatile fatty acids (VFAs) concentrations) were also examined. This was compared with mono-digestion of SCC. The experiment was performed with different mixing ratios in reactors labelled as follows: A = 75 g SCC + 5 ml CU; B = 70 g SCC + 10 ml CU; C = 65 g SCC + 15 ml CU; and D (control) = 80 g SCC at a hydraulic retention time of 42 days. Co-digestion (SCC + CU) significantly improved anaerobic digestion (AD) performance resulting in a threefold and fivefold increase in biogas and biomethane production, respectively, with concomitant TS (44.9–57.7%) and VS (55.4–60.3%) removal efficiencies. But for mono-digestion (control experiment), all CU treated and co-digestion assays showed pH stability ranging between 6.6 and 7.4 and VFAs’ concentrations ranging from 15–330 mgL-1. By acting as a buffer, CU effectively enhanced the AD performance of SCC as demonstrated in this study.