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Sustainable treatment of fecal matter is a long-standing challenge in sanitation, particularly in developing countries. Although recent developments have seen the evolution of innovative onsite sanitation technologies, the treatment of fecal waste collected still remains a daunting task. This study evaluated the effect of formulated feedstock: fecal matter from urine-diverting dry toilets and kitchen waste (1:0, 1:1, 2:1, 4:1, and 0:1) on waste weight reduction, Hermetia illucens’ larval weight gain, and crude protein content during co-digestion. Samples were collected after every 2 days for larval weight determination and protein content analysis using the Kjeldahl method of nitrogen determination. The waste reduction index (WRI) was determined after 50% pupation. The larvae grew on all substrates yielding 32.97–38.6% dry matter (DM) protein content and larval weight ranging from 1.12 to 1.70 g per five larvae. Results indicate that a 1:1 co-digestion ratio resulted in a high WRI (3.61), DM crude protein content (38.6%), and larval weight (1.70 g per five larvae). This study used the circular economy-based approach which provides a win–win situation to sanitation provision and environmental management while realizing products with potential for livelihood improvement. HIGHLIGHTS A system for simultaneous co-digestion of the urine-diverting dry toilet fecal matter and kitchen waste for animal feed protein ingredients was investigated.; Hermetia illucens’ larvae developed in all rearing substrates provided despite the substrates' elemental composition.; Co-digestion of fecal matter increased process performance of H. illucens’ larvae.; Co-digestion significantly increased larval protein content and weight.

Anaerobic digestion is a highly complex process, particularly in co-digestion between poorly-defined, complex co-substrates like distillery wastewater, molasses, and crude glycerine. Thus, in this article, the authors tackled the problems by using Monod two-substrate with an intermediate (M2SI) model to represent accumulated biomethane evolution (ABE) obtained from the co-substrates, including easily degradable, slowly degradable substrates and intermediate. The M2SI model predictions were compared with the traditional Monod model's simulation results to clarify an outstanding of the present model in the aspect of modeling and control. Different behaviors of ABE curves from batch experiments were used to calibrate the M2SI model prediction with sensitivity analysis of the model parameters. It was found that the M2SI model gives a correct trend to describe the co-digestion process with multiple substrates and complex microbial activities with satisfactory fitting accuracy. At the same time, simple Monod kinetics have a good fit for dilute pure distillery wastewater, but the estimated microbial growth kinetics were counterintuitive. Therefore, the M2SI Model has a broader range of applications for co-digestion dealing with the complexity of multiple microbial activities to consume inherently complex or artificial co-substrates.

For small-scale wastewater treatment plants in rural areas (WWTPRs) of Japan, reducing sludge disposal costs is an important issue. Co-digestion of sludge from WWTPRs and food waste is a promising method of reducing maintenance costs and producing energy resources such as methane. In this study, co-digestion experiments using sludge and kitchen garbage were conducted to investigate the stability of the co-digestion from the perspective of trace metal requirements. The gas production rate and pH were stable in the digester with HRTs of 140–70 days. With a HRT of 30 days, the pH gradually dropped from 7.0 to 6.5, and VFA accumulated up to a concentration of 2,200 mg/L, indicating process failure. Cobalt (Co) concentration was approximately one-tenth of the required amount reported by a previous study. When Co was added to the digester, the pH and gas production rate became stable even with a higher VS loading rate. Therefore, the unstable situation was attributed to a lack of Co in the sludge. The Co concentration of sludge from WWTPRs in Japan is generally low, similar to the sludge used in this study. The addition of Co is required for stable co-digestion of sludge from WWTPRs and food waste.

Biogas production has been suggested as a valid valorization solution for microalgal/bacteria biomass (MAB) grown on wastewater. This research is aimed at assessing the feasibility to use MAB grown in an outdoor raceway fed on piggery wastewater for biogas production. Batch and continuous anaerobic tests were conducted on the sole MAB and on a blend of MAB and carbonaceous substrates (deproteinated cheese whey and cellulose) to improve the carbon/nitrogen ratio. Results of batch biochemical methane potential tests confirmed that the sole microalgal/bacteria biomass was poorly degradable (119 NmLCH4·gCOD−1), while blending it with deproteinated cheese whey or cellulose (80% of carbonaceous material and 20% of MAB, as chemical oxygen demand (COD)) had no synergistic effects on the methane yield, although slight improvements in the degradation kinetics were observed. Continuous anaerobic degradation tests (at an organic loading rate of 1.5 gCOD·L−1·d−1, 35 °C and 30 days of hydraulic retention time) increased the overall methane yield from 81 NmLCH4·gCOD−1 (sole MAB) to 216 NmLCH4·gCOD−1 (MAB and deproteinated cheese whey) and 122 NmLCH4·gCOD−1 (MAB and cheese whey). However, data confirm that no evident synergistic effects were obtained.

Grease waste (GW) is an adequate substrate for sewage sludge co-digestion since, coming from a waste water treatment plant, it has a high methane potential (489 NmLCH4/gVSin); however, no synergistic effect takes place when co-digesting with 52%VS grease. Conversely, thermal hydrolysis (TH) improves the anaerobic digestion of GW (43% higher kinetics) and biological sludge (29% more methane potential). Therefore, the application of TH to a co-digestion process was further studied. First, biochemical methane potential tests showed that the best configuration to implement the TH to the co-digestion process is pretreating the biological sludge alone, providing a 7.5% higher methane production (398 NmLCH4/gVSin), 20% faster kinetics and no lag-phase. Its implementation in a fed-batch operation resulted in considerable methane production (363 NmLCH4/gVSin) and TH improved the rheology and dewaterability properties of the digestate. This leads to important economical savings when combined with co-digestion, reducing final waste management costs and showing interesting potential for full-scale application.

The objective of this study was to compare methane production and characteristics of digested material in anaerobic digestion concepts according to the Animal By-Products Regulation (ABP-Regulation) of the EC (hygienisation of biowaste for 1 hour at 70 °C, particle size

This project furthers the understanding of co-digestion of organic waste with wastewater solids, quantifies the benefits of co-digestion, and provides answers to key questions to help overcome barriers associated with greater implementation of co-digestion programs at municipal WRRFs. The practice of adding waste organic feedstock directly to anaerobic digesters is becoming an attractive way for utilities to generate revenue from tipping fees while boosting biogas production. However, the practice is only used by about 20% of WRRFs with AD due to the uncertainty on how to proceed without causing digester upset. Through lab, pilot-scale, and a study of a full-scale facility, this research addresses some of these operational issues. Includes an Excel-based Economic Model that utilities can use to determine an appropriate tipping fee for handling this waste in the digesters – often the source of additional revenue which makes these energy recovery project viable. This title belongs to WERF Research Report Series . ISBN: 9781780405384 (eBook)

The anaerobic treatment of sewage sludges (primary and secondary) mixed to concentrated soluble wastes (olive mill effluents, cheese whey and landfill leacheate) in conventional once-through and anaerobic contact digesters, has been investigated in laboratory scale reactors. Experimental results indicate that it is possible to increase appreciably (100 %) the volumetric loading rate of sludge digesters (anaerobic contact) by addition of soluble substrates and keep stable operating conditions. The proposed treatment is economically very attractive if the load due to high strength wastewaters is of the same magnitude as the sludge load, as it does not require additional reactor volume.

The results of 2 years experiments on thermophilic single and two-phase anaerobic co-digestion process on activated sludge and agro-wastes are presented. Solid agro-waste (mainly fruit and vegetable residuals from markets) and waste activated sludge were used as substrates. A pilot scale CSTR of 200 l working volume was used for single phase test, while an 0.8 m3 digester was added to study two-phase experiments. Treating only wasted sludge, the initial organic loading rate (OLR) was 0.7kgTVS/m3 d; then it was increased up to 2, 4 and 6 kgTVS/m3 d by OFMSW addition. Following OFMSW increase in the feed, it was found out the increase of GPR from 0.12 to 3.12 m3/m3 d and SGP from 0.16 to 0.51 m3/kgTVS in single phase. The stability of the process was showed also in the most critical operative conditions. Two phase experiments didn't show important differences to the single phase test in the range of OLRs studied up to now (up to 4 kgTVS/m3 d), clearly showing that these are not critical conditions for the process, that can be carried out in single phase in all the range studied. Considering the option of retrofitting the anaerobic digesters of the existing sludge line in WWTPs, the obtained data give important indications about process feasibility.

The anaerobic co-digestion of high strength industrial wastewaters in centralised plants receiving effluents from various local small scale industries is considered to be superior than individual small scale treatment plants. An approach is proposed to systematically tackle co-digestion problems, with respect to both biological and engineering models. In a steady-state mathematical model presented, the effect of combining wastewaters in mixtures, based on major component groups ( i.e. lipids, hydrocarbons and proteins), is systematically accounted for. The model is then solved via a non-linear optimisation program (NLP) which results in the determination of an optimal design of the necessary reactors and their respective layout, by balancing the natural trade-offs between reactor and post-treatment costs (due to high pollutants emissions). The preparation of appropriate mixtures is the major parameter controlled. The applicability and potential of the model are demonstrated with a small example.