Co-Author of “Treatment of Food Services Establishment (FSEs) Effluent by Physico-Chemical Treatment: A Case Study for Trinidad & Tobago”
Meet Eng. Shamika Cudjoe, R.Eng.—a rising leader in Environmental Engineering whose research is shedding new light on one of Trinidad and Tobago’s most pressing wastewater challenges. Her work on FOG (Fats, Oils & Grease) treatment offers real solutions for national infrastructure, sustainability, and public health.
Environmental engineering is one of the fastest-evolving frontiers of the profession—where science, technology, and sustainability converge. Among the new generation of professionals shaping this field in Trinidad and Tobago is Engineer Shamika Cudjoe, a Manager with the Water and Sewerage Authority (WASA).
Her recent joint research, conducted in collaboration with the Indian Institute of Technology (IIT) Varanasi, examined the treatment of Food Services Establishment (FSE) effluents—focusing on the removal of Fats, Oils, and Grease (FOG) using physico-chemical methods. The study highlights a serious but under-addressed issue: thousands of litres of untreated restaurant wastewater, rich in grease, flow daily into the national drainage and wastewater system.
In this conversation with the BOETT, Eng. Cudjoe discusses her professional journey, the significance of her research, and how young engineers can contribute to building a more sustainable future.
Q1. What inspired you to pursue a career in Civil and Environmental Engineering?
My answer would be more pointed to “who” inspired me to pursue a career in Civil Engineering. It all started whilst chatting a day with my athletic peers of the Memphis Pioneers Club at St. Mary’s Grounds, about where I can find an Advanced A Level mathematics lessons teacher. Hilarie Roach, responded enthusiastically that Mr. Arden Enrique Willams aka “Gunn” would be perfect and was located in the St Clair area, close to our training grounds at the time. That evening, I told my parents about the recommendation I had gotten, and they launched their inquiries. It so happened he attended Queen’s Royal College with my uncle Mr. Alvin Daniel, where they both went on to pursue Engineering. My uncle took me to Mr. Williams’ lessons place the next day, and the rest was history. Mr. Williams’ teaching style and overall lessons on life didn’t just draw us close as protégé and mentor but laid the path for much of who I am in my career today. The discipline, problem solving skills and dedication to the profession. In summary, Mr. Willimas didn’t just ensure I got an A in A Level Mathematics in my lower six year, but he ensured I would eventually pursue engineering in the years ahead, even in his absence. My dedication in my Phil Research Publication, is to him.
Q2. Tell us a bit about your journey to becoming a Board Registered Engineer in Trinidad and Tobago. How did that achievement shape your professional outlook?
My journey to becoming a Board Registered Engineer was quite interesting and took off whilst working at the Water and Sewerage Authority. It must have been circa 2012/2013 when a gentleman by the name of Mr. Carl Haynes often conducted business at the New Services Department (where I worked at the time) of WASA. Mr. Haynes and I would not only talk about designs for developments he was overseeing, but the conversations often took paths of overall engineering and technology. It was during these conversations that he encouraged me to become a registered engineer and even brought me a registration form. During his visits to New Services, he would often inquire if I had completed the registration package so that he can submit on my behalf. I eventually did, however, having a MSc. Environmental Engineering didn’t qualify me, as my first degree was BSc. Double Major Physics and not engineering. Mr. Haynes told me if I were to obtain the MPhil, I would definitely be successful. I was already in the process of pursuing an MPhil programme at the time. Upon completion of the Mphil in 2018, I was happy to tell Mr. Haynes that I resubmitted the application to the BOETT. He was elated to hear such. He was even more elated when he heard I was accepted to be registered by the BOETT.
This achievement was extremely meaningful, especially knowing/experiencing the diligence and commitment of the Board in maintaining engineering standards. This was reinforced by the Code of Ethics that I got in the acceptance package, that spoke strongly to engineering ethics and what engineers mean to society and its future. We are problem solvers; we fix the world! What a great responsibility it bears to be an engineer.
Q3. How did the idea for this research on Food Services Establishment (FSE) effluents first come about?
This idea also came about whilst working at the WASA as the Industrial Services Officer. Then I realized that Fats Oils and Grease (FOG) or trade effluent from Food Services Establishments (FSEs) had plagued the wastewater infrastructure, resulting in costly operations and maintenance works, hygiene and sanitation issues, traffic inconvenience for sewer repairs, illegal dumping etc. I became very interested in solving this problem, noting that there was no viable solution to the problem at the time. I decided this would be a problem that can have several positive impacts once solved.
Q4. What gap or problem in local wastewater management were you hoping to address with this study?
The problem to be addressed was to find an engineering method/approach to break down trade effluents from FSEs into an environmentally friendly form for disposal, as the only method present everywhere was pre-treatment via grease trap/interceptors. However, these plumbing systems are only designed to prevent FOG from Food Services Establishment from directly entering the sewer systems and did not offer treatment or breakdown of the FOG. Upon exploring further, it was noted the problem to be addressed was complex and therefore evolved as I would further explain.
During literature review for the MPhil, it was noted that effluents from FSEs would generally come into two categories Oil or “spent shortening” and grease. During my time as the Industrial Services Officer, I realized that the public education on disposal of the Oil in Trinidad was fairly known, where the used oil would be placed in kegs and was collected by one or two companies known at the time for collecting and recycling oil. I was allowed to visit one of the companies at the time, and their principle surrounded centrifugal force, where the used oil was spun in a system, removing particles in it. This would then be shipped abroad for further processing and eventual conversion into bio fuels.
The problem of grease, however, did not have a viable solution, two of the companies that had treatment systems locally were visited. Methods utilized were microbial and dissolved aeration flotation (coagulation and flocculation included), polishing ponds and soil beds. However, these systems faced numerous issues and even failures, to which these companies were also exploring another method of treatment. International studies were then looked at where it was realized, that grease in itself had different aspects that were studied for treatment. These aspects constituted the aqueous layers of grease i.e., floatbales, emulsified and settables. International studies had varying results for percentage removal of Oil and Grease. In these international studies, optimum results were attained via a sophisticated experimental type set up by engineering students Qin et al in 2013 that used a pilot plant (electro coagulation and electro flocculation) with the aid of a centralized quadratic program which predetermined the optimum dosage requirement and therefore resulted in zero trade effluent.
After an intensive Literature review, it was decided the problem to be addressed would be the emulsified layer (toughest layer to be treated) utilizing a physico-chemical treatment process.
Q5. The paper notes that 260,000 kg/day of FOG-laden wastewater is unaccounted for in Trinidad and Tobago. How significant is this figure in terms of national environmental impact?
This accounts for 59% of trade effluent being unaccounted for from most of the registered FSEs at the time of study. This figure is grossly conservative, keeping in mind that this is the count of registered FSEs received from most of the counties, to which calculations were based on a minimum size grease trap for each FSE, throughout T&T. There are numerous unregistered FSEs, or persons catering from home, at schools etc. With that in mind, we can just think about the weight of 260000kg/ day in grease, scattered in the environment, sewer pipes and systems throughout Trinidad and Tobago. The Lange Park WWTP was out of operation many years ago, because of being laden with grease. To date, a considerable number of the daily customer complaints of sewage overflowing premises are due to grease found in the sewage infrastructure. The complaints often outweigh the equipment availability resulting in non-compliance by RIC standards of 18 hours for clearances of chokes, in the northwest area. This is the extent of the impact of FOG in the environment nationally. Let us keep in mind the TTS 638:2015, by the Trinidad and Tobago bureau of Standards, indicate permissible levels for FOG is 20mg/L. Therefore, let’s assume you have a grease trap size holding 500 US gallons (1.89 cubic meters or 1890 L) of fog bearing water, the weight of FOG allowed to flow in the sewers from that volume of grease trap would be 0.0378kg. Imagine that compared to a conservative figure of 260000Kg of unaccounted for grease daily.
Q6. From your findings, what are the most common shortcomings in how local restaurants and food establishments manage their grease and wastewater?
Public Education – This is a fundamental issue when coming to grease especially. FOG in liquid form appears harmless or doesn’t appear to the naked eye; however, when it cools it congeals and hardens and attaches to the inner lining of drainage pipes and sewers. Sewer pipes are made from hydrophobic and oleophilic materials which mean water does not stick to the material, but oily substances are naturally attracted to the material. This results in oil and grease clogging pipes resulting in sewage overflows which cause damage to properties and also pose a health threat. As such, knowledge of having a grease trap, knowing how to maintain it and the impacts, were not widely known during my time of conducting inspections and the study.
Reinforcement by Local Authorities – Visual inspections and penalties need to be revisited between the Public Health Inspectorate and the Water and Sewerage Authority. The main issue here tends to be these bodies being tied by the Acts that have been archaic.
Q7. Could you explain, in simple terms, what coagulation-flocculation treatment is and why it was chosen as your focus?
Coagulation (rapid mixing) is generally described as the process whereby colloids (grease in water) are destabilized by a cationic substance, which is complemented by flocculation (slow mixing) that allows flocs to agglomerate and hence settle out. Colloids of oil and grease (usually negatively charged) are hydrophilic (interaction is favorable with water having a tendency to mix) and thus frequently require special treatment to achieve effective coagulation. Consequently, coagulation is induced by the addition of high valence cations. The main objective of coagulation in emulsions is to destabilize the colloid by neutralizing it. This process occurs during rapid mixing. Flocculation is done via slow mixing; here the particles agglomerate to from large flocs. Polyelectrolytes are used to encourage floc build up in flocculation, which then allows the settling out of the grease.
The most consistent and effective results were seen from the physico-chemical treatment processes which are dominated by electro coagulation and flocculation.
Q8. Your study found 99.9% removal efficiency for FOG using specific treatment conditions. How significant is that result compared to conventional practices?
The Jar test produced 99.9% removal of FOG with a final effluent concentration of 0.17 mg/l, which was well within the regulatory standard of 20 mg/l. This is more than desirable compared to not only the standard but also other conventional practices in Trinidad, which were shown to exceed the permissible level during the time of the study. However, it shall be noted that results for FOG removal were less efficient for the Pilot Scale Study. The plant was able to achieve a 97.4% removal of FOG (an effluent level of 16.8 mg/l). Limitations were faced with the agitator type used for flocculation i.e. propeller type instead of flat blade turbine. Even with the limitations, the percentage removal and effluent level were within the permissible level, which are significant results compared to conventional practices in Trinidad.
Q9. What were some of the biggest challenges you encountered during sampling, bench-scale testing, or pilot plant trials?
The biggest challenge faced was during the Pilot Scale Trial. Equipment proved to be a limitation as mentioned earlier. The blades available for flocculation were undersized and not of the correct specification (agitator type vs flat blade turbines). Compensation was made in the number of blades utilized, however, the baseline results achieved in the Jar Test were not achieved at the Pilot Scale Study. To further compensate for the mechanical limitations, alternative chemical strengths were looked at for the polyelectrolyte used during flocculation, which attained a more desired result. This is in alignment with theory, where factors critical for agglomeration are equipment type and density charge. It should also be noted that, critical parameters for the settling times were also altered, in the pre-sedimentation tank and primarily in the final settling tank.
Q10. What do your findings suggest about the current state of grease trap design, maintenance, and enforcement in local FSEs?
The findings suggest that grease traps are generally poorly maintained, enforcement is scarce, resulting in significant unaccounted for FOG being released into the environment daily. Consequences of which are exceptional amount of unbudgeted operational costs for WASA and an overall health concern for the environment and public. The study however offers a solution for safe disposal of grease laden waters in Trinidad and Tobago, thereby allowing stakeholders such as FSE owners and haulers, to safely dispose of this waste. As such, authorities like Public Health and WASA can be more rigid in their approach/enforcement for the maintenance of pretreatment systems like grease traps.
Q11. Are there any national standards or regulations that should be updated to better manage FOG disposal?
TTS 638:2015 doesn’t require updating in my opinion, however, the WASA Act for enforcement and penalties associated with this standard requires updating.
Q12. How can agencies like WASA, the EMA, or local corporations benefit from this research when addressing recurring sewer blockages or wastewater plant inefficiencies?
This research is beneficial in providing an option for not only disposal but treatment of the emulsified layer of FOG at a reasonable cost for implementation as reflected in the study. This would be more economically viable than the hundreds of thousands of dollars spent on operational and maintenance costs on plants and sewer infrastructure annually due to damages caused by excessive release of FOG into the sewer system. Pollution to open bodies of waters and its impact on flora and fauna would also be significantly reduced, as illegal dumping would be on a decline. In summary, there would be multiple benefits to many stakeholders including the public and the environment. Revenue can also be looked at for bringing the emulsified water for treatment if this project becomes state owned. An all-encompassed socio-economic benefit to all.
As it pertains to the other two layers, incineration and acid digestion have been already studied for the successful treatment of the floatable and settable layers. Cost analysis can be looked into. The study also analyzed the sludge arising out of physicochemical treatment and showed it to be heavily water based and high in aluminum content. As such, it can be disposed of via dewatering or digestion and any remnants can be disposed of via Caroni Water Treatment Plant which has internal methods of disposing of this type of sludge waste. Research on sludge with this concentration of aluminum also reveals that it can be used for cement mortar and concrete making.
Q13. What steps do you believe Trinidad and Tobago should take to move toward sustainable wastewater management across the commercial food industry?
Fundamental Steps would be as follow:
- Public education on plumbing approvals, Standards such as WPR 2019 and Trade Effluent Discharges into Sewer Systems, impacts (environmental and financial) of poorly maintained grease traps and pretreatment systems.
- Haulers to be certified for FOG disposal/trade effluent. Log systems to be implemented at FSEs and disposal sites for all certified haulers of FOG.
- Implementation of a treatment system for all 3 aqueous layers of FOG.
- Revisions of penalties by the Authorities for persons in breach of FOG disposal as per the respective acts and regulations.
Q14. What role do you see for interdisciplinary collaboration—between engineers, policymakers, and the private sector—in tackling wastewater management issues?
With all stakeholders actively involved the steps proposed earlier can be easily and quickly implemented. With the treatment system constructed and commissioned, change in Acts/Polices and public awareness, the overall problem that plagues our infrastructure, environment and the general public, would be solved in the shortest possible time which is the end goal.
Q15. Finally, how do you see your role evolving as a Registered Professional Engineer contributing to national development and environmental stewardship?
My role as a Registered Professional Engineer is to serve the profession and Country when called upon and as required within the bounds of my engineering capacity. That would be my opportunity to return the knowledge and education imparted to me; all toward improved development and a sustainable environment in Trinidad and Tobago.