International Journal of Scientific Research in
Environmental Science and Toxicology

Unsegregated heterogeneous mass of solid waste is a potential threat towards the safe processing and disposal of municipal solid waste [MSW], which is cumbersome and ancillary, elevates the expenditure. The absence of any pertinent technique to handle these bulky mass in an eco-friendly way makes it even more hectic for the MSW processing plants. But, this substantial mass constitutes a huge potential, which can be valorized through the larval digestion of a symbiotic macro culture, to create new economic niches for smallscale entrepreneurship in developing and under-developed nations. The present study incorporates a symbiotic waste reduction system with the efficient functionalism of micro and macro conversion agents which is attributed to the synthesis of waste derived co-products from the same platform. This study is solely a novel approach, which is capable of addressing a wide fraction of solid waste, domestic sewage, and bio-leachate and converts them into value-added coproducts within the magnificent period of time. Multiple experiments have been conducted under the controlled feeding environment with an established symbiosis between the BSF larvae, Wax Moth larvae [Galleria melonella], and effective microorganism culture. An initiation period of 5 days was allocated for the macro conversion agents and during the tenure, the larvae were supplied with synthetic diet to accelerate the body growth index. The entire experiments have been conducted in a newly formulated novel bioreactor namely, Integral Larval Grub Composting Reactor which is capable of performing automated pupal segregation and address solid and liquid waste under a single platform. The system enforces the zero liquid discharge concept and also helps in an indirect suppression of house fly growth. The novel approach only required 14-16 days in order to convert the solid waste into nutrient-rich manure, having significantly high-quality component. The operation has been executed in a number of batch processes and each process valorized a quantity of approx 30 kg. The targeted larval period has been prolonged by means of maintaining higher moisture content with the help of sewage supply and once the maturation period arrives the further addition of moisture has been restricted for 3 days. Overall it’s an ultimate and wholesome biological waste management technique, which is capable of standing solely to strengthen the sustainable waste management strategy.

Keywords: Galleria melonella; Hermetia illucens; Larval period; Moisture; Plastic waste;

• Symbiotism has been established between the larvae of Hermetia illucens and Galleria melonella.
• Excessive Moisture prolongs the targeted larval instar stage.
• Larval culture degraded heterogeneous solid waste including plastic.
• Solid and liquid waste was efficaciously treated under a single platform.

In lower and middle-income countries it has been observed, in contrast of other inorganic and inert waste which has a potential value to the rack pickers and recyclers the quantity of generation of organic fraction is predominant [i.e. amounting to 65%]. But it has been rarely seemed to be forwarded to the treatment facilities or considered as significant source of revenue generation unlike the other part of MSW, though in some occasion it may get collected, but its ultimate fate is always in dilemma and either it usually ends up in receiving landfills or on a relatively unscientific open dumping in outskirts of the town, where the material get degraded in the form of large piles under anaerobic environment [1, 2]. Ultimately a feasible treatment has been replenished in the form of BSFL composting, which minimizes the environmental interventions and advances the aspect of public health and sanitation. This novel and economically feasible waste management approach need to be implemented and promoted for overall good [3]. Finally, when it comes to the compost phenomenon, it has been already explored by several researchers all over the globe. On the other hand availability of the relevant literature and information is very meagre in the case of microfauna. As far as the Indian scenario is concerned, assortment and functionality of this macro-organism was studied in recent past. Ritika et al. has tried to establish a correlation between micro and macrofauna and reported that, once the pre-decomposition get completed [15-20 days], the partially decomposed material can be supplied to the earthworms namely, Eisenia fetida to examine their interface with the BSFL [4]. But as per the environmental conditions, rearing of BSF should be keenly observed and monitored, because it is rarely hectic in India as larvae thrive better in the tropical environment, hence composting utilizing BSFL should be recommended in India for sustainable waste management [5].

The requirement of formulating an alternate and sustainable waste management strategy for Chidambaram provoke the idea of using the Black Soldier Fly Larvae [BSFL] composting. Rather than the waste treatment and minimization, the above process is also capable of addressing multidimensional issues such as rising demand of implementing renewable fuel, increasing protein in farm and aquatic diet, yielding compost with high nutrient content, etc. Other major advantages comprise higher consumption rates and faster rate of degradation and bioconversion [6,7]. Trinh et al. performed experiments on nutrition conditions with different substrate sources and reported the larvae were capable of degrading the wide range of wastes such as control poultry feed, pig manure, kitchen waste, fruits, and vegetables, etc [8]. But the optimum reduction was observed in the case of poultry manure which yields healthier black soldier flies with lower mortality rates. Diverse rates and the relation between conversion efficiency and larval growth have been recorded by several researchers. Nevertheless, in order to suboptimize the value of these two key factors of BSFL composting, experiments have been conducted by feeding the larvae with four different concentrations of dairy manure to predict its influence on the life cycle traits of larvae as well as adult files to establish a relation between supply rate and BSFL growth [9]. The results reveal that the feeding rate has major impacts on larval and adult fly development and nutritional profile and it showed a proportional relationship in which larvae with greater substrate availability weighed more than those fed significantly lesser ration. Collaterally, Stefan et al. stated that an average prepupation rate of 252 g/m²/day [wet weight] was achieved under optimized environmental conditions and the bio-conversion yield around 65.5 to 78.9% depending on the quantity of waste added on regular basis and also by the availability of the drainage facilities [10]. Stefan et al. have observed that the optimal balance between treatment efficiency and biomass population can be maintained by a proper nutritional diet and feeding rate on a day to day basis, spiked by a moisture content of 60% [11]. The above study also observed the rate of biomass production for different sorts of substrates and stated that an individual waste stabilization component can produce a pre-pupal biomass of 145 g [dry mass] per m² on a regular basis. Contradictorily, Myers et al. have encountered significantly lower conversion rates [12]. A bio-kinetic study was conducted to understand the correlation between the growth kinetics and feeding rate and stated the reduction in weight of dry matter varied inversely proportional to the waste loading rate. They observed in a lab-scale study when the larvae fed 27 g of waste on regular basis it reduced the dry fraction approximately by 58% while the other experiment yields considerably lower conversion rates [i.e. 33%], where larval feeding rate was increased by 70 g of waste matter/day. The increased larval feeding rates also found contradictory in the case of life cycle studies, it accelerated the mortality rates to 29% from 17% among larvae. Apart from this conventional feedstock, the technique is also capable of addressing awfully complex secondary wastes such as bio-leachate, persistent pollutants etc. This comprehensive management ability helps the treatment to emerge as a wholesome alternative [13]. Hang et al. studied the economic feasibility of the above technology and reported; raw swine manure can yield up to 95–120 kg of larval population per m³ of waste supplied to the system [14]. The study also claimed that the live and fresh biomass can be served as an optional animal diet, rich in protein and fat content. As well as it is feasible in capturing the nutrients from the waste stream which can be further utilized as agro-based plant manure and the bioconversion technique stabilizes the primary pollutants and minimizes the production of obnoxious gases and odour formation by 94.5 %. The economic proficiency of the above technique even makes it more feasible with the yearly profit rages from US$33.4–46.1 per m³, observed during the operational period. In order to interpret the above scenario, an experimental study conducted by Tschirner and Simon may be considered as a benchmark [15]. They have investigated the influence of different growing substrates on the crude nutrient and they observed the impact of different fodder consumption on the larval body composition. They reported the yield of different nutrients for the experimental period of 15 day, where protein and fibre value ranges around 0.93 and 0.43 kg of wet mass, respectively.

On the other hand, wax moth larvae found to be feasible for biodegradation polyethylene, which comprises approximately 40% of the entire plastic mass and the consumption rate reported to be comparatively higher. A group of researchers from Spain and England stated that the 100 counts of larvae can efficiently degrade 92 milligrams of polyethylene within a period of 12h. It has been reported in the same study that the presence of ethylene glycol was observed during the enzymatic conversion process, which signifies biological breakdown of the polyethylene [16]. Contradictorily, Weber et al., stated that the results showcased by the previous author is uncertain and not substantiate with enough scientific evidence [17]. Precisely this research group has questioned the interpretation of the signals obtained by infrared spectroscopy which assures the presence of ethylene glycol.

Eventually, the entire research community has been agreed to validate black soldier fly larvae as the most unique and profitable conversion and stabilization agent of the new era with minimal hindrance. The technique is rampant and further research in this domain may help the lower middle-income nations to get read of the unsightly and unscientific dumping yards.

The objective of this research was to primarily investigate the influence of different external conditions on the target larval instar stage and also to emphasize the superiority of symbiotic composting over the conventional, time-consuming and primitive methods and also to address the existing lagging and drawbacks in this domain and to explore the fraternity with the portrayal of ultimate treatment system, capable of accounting multidimensional aspects such as solid waste and sewage sustainably under a single platform.

Preparation of medium is a delicate issue and seeks utmost attention to germinate the mother culture. The medium should be such that, it ensures optimum body growth attributed to minimal mortality rate. Two different types of media were prepared that are delineated in details in followings.

In order to germinate mother culture, different mediums were prepared and used [Figure 1]. The body growth factor and the eating capacity for BSFL have been increased by initial feed acclamation in the form of partially degraded mixed oilcake supply enriched with Bio Nitrogen, Phosphorus, and Potassium. Four different types of cakes were used which has been prepared using different sources such as, mastered oilcake, groundnut cake, copra cake etc. They were soaked in water [i.e. 50:50 mixes] for the period of 24h under anaerobic condition and allowed the initial degradation. Then four different mediums were prepared by mixing the partially graded slurry in different ratios. The first medium incorporated all three different varieties in one third mix ratio, whereas other two consisted of mastered oilcake and groundnut cake in 1:1 mix ratio and copra cake and groundnut cake in 1:1 mix ratio. The last medium comprised solely mastered oilcake inoculated with cow dung. All the mediums were placed in an MSW processing and disposal facility namely, HiMSW, Hyderabad.

The other variety of medium was prepared using poultry litter, spiked with chicken intestines. The medium was kept in a fenced farmland nearby a stagnant algal pond under a controlled environment.

Wax moth, basically a pest of honeybees which feeds on the honeycomb. The raw honeycomb is expensive and thus is not a feasible option for regular usage in order to cultivate the larvae of Galleria melonella. Therefore a synthetic diet was prepared with the help of the following ingredients namely, Atta [1kg], Wheat bran [1kg], Cornflour [776g], Honeycomb [200gm], Yeast [80g], Honey [1.5l], Glycerol [1.2l], Milk powder [200g] [Figure 2]. Once the entire moisture gets evaporated from the synthetic substrate then larvae were separated from the system manually and introduced to a freshly prepared medium.

A complete and wholesome treatment facility is obligatory to meet the goal of sustainability and integrated waste management [Buiani 2015]. Thus, a treatment unit capable of addressing wastewater and solid waste under a single platform named, Integral Larval Grub Composting Reactor [ILGCR] was fabricated and the schematic has been portrayed in [Figure 3].

The reactor consists of two major working elements namely, waste conversion/maturation element and liquid circulation and recirculation unit. Rest of the subordinate units is there to support the fundamental working procedure. [Figure 4] shows the overview of the bioreactor. It comprises two upper-head tanks with the flow regulators, a sprayer, a grub composting area, pupal segregation and removal bucket, leachate drain with stopper, and a leachate collection tank with a recirculation system. Two peristaltic pumps are required in order to run the operation in continuous mode.

Initially, the waste got introduced into the active composting zone, where larvae were working upon it and decompose the waste. Near to the top opening four hinges has been provided to captivate the entry of larvae in unwanted zones and regulates the larval movement only towards the pupal segregation bucket. A leachate drain has been provided with a regulation system to drain the percolated bio-leachate from the system. A slope of 200 has been provided with the horizontal towards the drain opening. Pupal segregation bucket segregates the pre-pupae from the juvenile larvae and it comprises an exit hole to take out the same. A fall down slot of 1.5-inch length has to be given on both of the corners of the reactor. The upper-head tank placed in the top left corner of the reactor is meant for bio-leachate supply, which has a flow regulator in order to control the inflow volume. The other upper-head tank placed on the top right-hand side of the reactor is meant for sewage supply. The similar kind of flow regulating provision has been given to it. The moisture supplied from the upper-head tanks finally reach the sprayer and get uniformly distributed over the solid sample. A bio-leachate collection tank with influent flow regulator is placed near the bottom of the reactor. The inflow regulator only opened once in three days, once the leachate gets thickened. At the junction of the reactor and the leachate drain pipe, a fine mesh needs to be used to arrest the entry of larvae into the drain pipe. Two nos. of the peristaltic pump has been attributed to the system to convey the bio-leachate and sewage from the bottom tanks to the upperhead tanks. Altogether, the commercialization of the bioreactor may create a revolution in integrated waste management facilities and open new economic niche for small-scale entrepreneurship.

The heterogeneous and unsegregated solid waste was initially screened with the help of trammel, which has a 70mm permeate size. The permeate was collected and manually segregated for further treatment. The lumpy and inert materials such as cardboard, glass, metals were segregated out from the system. The rest of the mass which incorporates organic fraction and the plastic waste was sent to the ILGCR.

The process leachate and the brown water was collected from the HiMSW, Hyderabad and sorted in the upper head tanks. Primarily the system was boosted only with the help of sewage [i.e. 3days] and once the culture got acclimatized with the initial concentration then the process leachate was supplied for the rest of the period [i.e. 10 days]. Once the maturation period reached the addition of moisture was completely restricted.

The drainage facility was attributed with a gravity flow. A chicken mesh with 1mm pore size was used to arrest the larval movement into the drainage pipe. The drain pipe consists of a control valve, which was opened once in three days to provide ample period for quantity reduction and quality concentration.

The major perspective of the present study was to identify the feasibility of a symbiotic culture in heterogeneous waste degradation and the minimization of the conversion period.

The biodegradable fraction of the waste mass was converted and stabilized with the help of BSF larvae and an effective microorganism culture [i.e. consists of six different organisms namely, Pseudomonas fluorescence, Pseudomonas straiata, Bacillus substillis, Bacillus pumillis, Lactobacillus, Bakers yeast]. The study reveals that these voracious eaters initially consumes the readily biodegradable fraction of the waste and simultaneously goes for the other materials based on the stiffness and hardness index of the material. The conversion rates observed to be 280 mg/larvae/day which is slightly higher than the values reported by Diener et al. [18] [Figure 5]. The phenomenon of higher feeding rate was interpreted as the fusion of bio-leachate and enzyme accelerates decomposition process and converts the waste mass into easily digestible monomers which helps the conversion agents to consume the substrate at an elevated rate. In this context temperature found to play a significant role which hugely influences the conversion rates as reported by Stefan et al. [10]. The study indicated a sharp declination in the treatment efficiencies once the temperature dropped near to 21°C [19].

Greater wax moth caterpillar requires an initiation period of 5 days after emerging out of the hatched eggs. The polyethylene consumption rates were found to be successively increased until 30th days of the larval instar stage which rages approx 0.027g/larva/day [16] [Figure 6]. But, in absence of the primary food resources, the consumption rates found to get depleted simultaneously to a value of 0.009g/larva/day for 50 days old larvae [Figure 7]. Thereafter, a constant absence of raw substrate results in exoskeleton formation and pupal conversion.

Liquid waste was supplied in the form of sewage and process leachate to maintain the optimum moisture for enhanced biodegradation. The supply of liquid waste, reached the active decomposition zone was in three forms namely, solely sewage, pure leachate, and a 50:50 proportionate mixture [20, 21, 22]. The quantity of liquid waste introduced to the system found to be consumed at a rate of 69.75% at utmost between an interval of 3 days [Figure 8].

Maintaining a specific level of moisture in the system found to be correlated with the treatment efficiencies and body mass index of the larvae. The present research work has undertaken the influence of the moisture level on the behavioural characteristics of the larvae and as a major breakthrough prolongation of the targeted larval instar stage was recorded with an optimum moisture level of 68% [Figure 9]. Any further increment in the moisture level impacted negatively and accelerated the mortality

rate. The maximum prolongation [i.e. 29 days] attributed to optimum moisture level found to be approx 81% higher than the normal larval period of 16 days. This prolongation of the larval period also resulted positively with the body mass index of the larvae and the larvae used in ILGCR as operational agent found to grow almost double than a normal BSF larva [Figure 10; 11] [19].

The research work explicitly revealed that the symbiotic culture is utmost feasible for the treatment of unsegregated heterogeneous mass. The stipulated treatment period and minimal energy input make this treatment a pertinent option as per the societal need. Furthermore, the newly fabricated novel reactor successfully prolongs the larval instar stage of the BSF and thus maximized the body growth factor which contributed positively towards the synthesis of value-added co-products from the system. Ultimately, the research yields a wholesome treatment system with zero environmental interventions which can solely resolve the waste processing and disposal issues in lower and middle-income nations.

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