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INTRODUCTION
A soil ecology based Constructed Soil Filter (CSF) technology called Soil Bio Technology (SBT) process for wastewater treatment was initially developed in the early 1990s and patented in 2002 (2037441 , ,2034252 ). The SBT process uses mud or soil of particle size less than 1000 micron as media with Geophagus Pheretima Elongata Earthworm (PEEW) ecology for media regeneration. SBT process requires ~2500 sqm/MLD due to low hydraulic percolation in soil media. SBT is capable of meeting the high quality standards required by NGT. However due to large space requirements and higher maintenance due to manual scrapping of TSS from top of filter beds, only some plants were constructed using the SBT process till date. Since 2005 further research in the use of Terrestrial ecology for waste water treatment pioneered the use of high hydraulic conductivity catalytically enhanced granular porous non soil biomedia (in lieu of mud / soil) with Acarine Orbatid Soil Mite (AOSM) Ecology to develop a novel high performance low space footprint Nature Based System (NBS) inspired by principles enshrined in the Global Carbon Cycle. The process called Continuous Advanced Mite Utilizing System (CAMUS) based on SBT process has been developed, deployed, patented and trademarked for commercial deployment. CAMUS process incorporates multiple process units, multiple patents licensed from patent holders for various aspects as described in this advisory. The space footprint of the CAMUS process is <600 sqm/MLD which is nearly one fourth of SBT and other wetland type nature based technologies and is equivalent to conventional technologies. CAMUS provides high quality treatment at low maintenance costs and has low space requirements approaching conventional aerated treatment technologies. Due to above mentioned factors CAMUS has been successfully deployed in many number of STP/ETP/FSTP projects across the country with smaller capacity ranging from 10 KLD to 6 MLD as on date. CAMUS can be constructed to any capacity on modular basis and scaled up for bigger capacities for larger cities. CAMUS is a proven indigenous technology for STP/FSTP/ETP projects and one the most installed Nature Based System (NBS) of wastewater treatment.
GLOBAL CARBON CYCLE (GCC)
SBT and CAMUS, both stemming from Global Carbon Cycle principles (GCC) illustrated in Figure 1, may seem alike due to shared garden aesthetics in projects. The time mentioned in the figure is the average residence time of carbon in that ecosystem. However, they differ significantly in media, ecology, and process units. GCC highlights carbon life distribution across ecosystems, favoring terrestrial over aquatic for superior energy efficiency. Water-based life demands 300 times more energy than land-based life. A typical human of 70Kgs is around 16Kgs of living Carbon. Earthly ecosystems support 650 billion tons of carbon-based life, while aquatic ecosystems sustain only 1-5 billion tons. Treating wastewater in terrestrial environments is more energy-efficient due to better oxygen availability in soil compared to water's low oxygen solubility and diffusivity. Conventional aerobic wastewater treatments rely on energy-intensive mechanical aeration, unlike CAMUS, which uses naturally available oxygen in catalytically enhanced granular porous mite ecology supporting media. Utilizing the CAMUS approach for aerobic organic degradation in terrestrial environments significantly reduces operational costs by avoiding mechanical aeration typically used in aquatic environments.
PROCESS FLOW DIAGRAM & UNITS
The CAMUS process features a typical flow diagram detailed in Figure 2. In FSTP plants, the sizing of Process Units changes due to higher COD/TSS loads, approximately 25000 ppm, compared to Sewage, which is around 500 ppm. A general rule applied in design is that 1 KLD Fecal Sludge equals 50KL of Sewage, whether it's for FSTP or combined STP+FSTP.
Inlet Stilling Chamber (ISC): Raw Sewage from the wet well enters the STP at a 6-meter height, entering an intake basin with an inlet stilling chamber (ISC) equipped with magnetic flow meters. An online analysis sampler tests various parameters of influent such as BOD, COD, TSS, TKN, TP, Total Coliform, and pH as required. After the ISC the water is passed through mechanical screens as described below. This is an optional unit which can be directly integrated into the Fine Screen Itself.
Mechanical Fine Screen (FS): This includes a Parabolic or equivalent Mechanical Fine Screen with varying bar spacing (3-6mm or 10mm in SS316) for efficient separation of floating and settling particulates. The screened sewage falls into an Equalization tank designed to handle peak flow, allowing sufficient volume. Advantages of Parabolic Screens include self-cleaning properties and reduced maintenance.
Equalization Tank (EQT): Designed to handle peak flows, ensuring subsequent process units function at Average Flow. It pumps water to a Tube Settler for separating suspended solids. EQT is not necessary for projects where waste water is conveyed via small bore sewers or where nallah waste water is intercepted as in such cases the flow equalization occurs naturally in side the collection system unlike conventional UGD.
Tube Settler (TS): Here, specially designed media aids in fast separation of TSS employing ballasted settling. The slurry, containing both organic and inorganic TSS, is removed. The TS is designed to achieve high separation efficiencies, employing biological phosphate removal mechanisms and optionally employing coagulants/flocculants dosing systems.
BioMounds (BM1 & BM2): These act as biological aeration engines, utilizing specific cultures to remove COD/BOD and facilitate Nitrification (in BM1) and de-nitrification (in BM2). The process involves percolation through bio media, achieving significant BOD/COD reduction, nitrification of Ammoniacal Nitrogen, and denitrification by harnessing COD.
Vermicomposting Bed / BioMound 3 (VCB /BM3): This area involves biological decomposition of volatile organics, physically dewatering primary sludge, and subsequent vermicomposting to produce compost rich in phosphates, useful as a soil conditioner.
Chlorine Contact Tank (CCT): The final treated water from BM2 undergoes further disinfection in a Chlorine Contact Tank using gas chlorine to reduce Fecal coliforms, ensuring safe quality. Gas Chlorination is an economically viable and validated disinfection method for larger STP plants.
REGENERATION OF BIO-MEDIA IN BIO MOUNDS
Process for regeneration of Bio-Media in Bio-Mounds is shown in Figure 3. Notably the Oxygen in Air present in the pores of the Biomedia is consumed by the Biofilm/Soil Ecology to oxidize the organic matter adsorbed from the wastewater on the Biomedia to regenerate the surfaces. This oxidation of organics in the BioMedia is a exothermic process that releases heat energy into the pore spaces leading to convective upflow of lighter warm CO2 rich air which is then naturally replaced with fresh air from the ambient.
CAMUS MASS BALANCE
STP RETROFIT
Older STPs such as Oxidation Ponds, Activated Sludge Process (ASP), Extended Aeration (EA), MBBR plants etc can be modified with CAMUS process if required to reduce the energy consumption and ensure compliance with NGT norms. In such cases typically the primary clarifiers, aeration basins, secondary clarifiers, sludge holding tanks, oxidation ponds and sludge drying beds of the existing facility are filled with appropriate volume of porous granular CAMUS media inoculated with specified AOSM cultures and catalysts. If the volume available in the existing structures is insufficient then either new BioMounds are constructed in the available space typically by creating retaining walls joining the intertankage spaces of the existing STP layout or the existing tankages are increased in height to accommodate the extra media. Post installation of media clarified waste water is distributed over the BioMounds using an appropriate static distributor Primary Solid Liquid separation via elevated Tube settlers to allow gravity flow into BioMounds may be additionally created if the same does not exist at the STP site. Primary clarifiers may be avoided if the underground network used is a small bore sewer network. In the small bore network the function of clarification and equalization of sewage required in the CAMUS process is undertaken at the interception tanks. The treatment of the septage of these interception tanks is undertaken at the VCB of the CAMUS plant.
The main advantage of retrofitting STP using CAMUS technology are as follows:
1. Reduction of electricity consumption by 70%,
2. Meeting stringent NGT norms for treated water, and
3. Ease of O&M and low maintenance due to lower Electromechanical CAPEX needed.
COMPONENTS OF CAMUS
The critical components of the CAMUS process such as 1) pre-treatment units, 2) Bio Media in the Bio Mounds, 3) Bio-Indicators such as plants and 4) Cultures and Catalyst inoculated into the Bio Media are installed on top of the Bio Mound / Bio Media Bed are shown in figure 6 and discussed as below.
Pre-treatment: includes Solid Liquid Separation, Chemical Precipitation via Flocculation/Coagulation (optional) and Flow equalization A) Parabolic Fine Screen (PFS) removing larger particles up to 3mm to prevent clogging of the distributors, B) Tube Settler (TS) to remove settlable sludge and an C) Equalization tank (EQT) to handle peak flow if there is a UGD feeding the system. Note typically nallah intervention projects do not need a EQT as the Nallah itself provides for equalization of flow. Secondly communities using Small Bore sewers do not need Pre-treatment (EQT and TS) in the CAMUS process as the equalization of flow and Sludge settling occurs in the Small Bore Settling tanks itself. In Small Bore Sewers, the fecal sludge pumped from the distributed settling or septic tanks is collected via vacuum honeysucker septiclean vehicles and discharged to the Vermicomposting system for processing. Other nature based interventions for pretreatment such as the SHEFROL (Patent 3022828) technology developed by Pondicherry University are also integrated.
Bio-Indicators: Health of ordinary non wetland/non aquatic Plants on the Bio Mounds and Fish in the treated water tank is used as an quality indicator of the performance of the Bio Mound and is an important facet of O&M post commissioning of the STP asset.
Bio Media: High hydraulic conductivity catalytically enhanced Porous Granular Mite Ecology supporting Bio Media is installed in the Bio Mounds (1/2) and VCB/BM3. CAMUS bio media is typically composed of 4 types of materials based on local availability a) WR: Weathered Rock (Indian Patent 4143398 ) b) FC: Fired Clay (Indian Patent 4143398 ) c) GF: Geo Foam/Fibre (Indian Patent Application: 202321002060 award awaited) d) RS: Red Soil (Patent 2034258 ). The Bio Media is the carrier of the Soil ecology and provides the essential function of providing a large bio regeneratable buffer capacity of adsorption and absorption uptake of dissolved organics from wastewater. A suitable mixture of the 4 types of media described above is formulated for installation to meet both organic load demand and hydraulic conductivity demands of the site.
Cultures and Catalyst: Acarine Orbatid Soil Mites (AOSM) Culture (Indian Patent: 414339) for Liquid processing in BM1 and BM2 and Pheretima Elongata Earth Worms (PEEW) cultures in the vermin-composting Beds (VCB/BM3) (Indian Patent 203744). The Catalyst (Indian Patent 414339) is an oxidation enhancing inorganic mixture of micronutrients required to enhance the oxygen exchange capacity of the bio media chosen. Other soil ecologies are being explored by researchers for use in future applications.
PROCESS CHEMISTRY
In this technology respiration reaction1 consumes the carbon of organics while mineral weathering reaction 8 & 9 captures carbon as carbon dioxide and by so doing regulates pH. The photosynthesis reaction provides ecology and sustainability for the process especially when STPs face intermittent loads in operations. Nitrogen of protein and other sources is converted to elemental nitrogen; reactions 10-12 describe the chemistry. The CAMUS reactors can be configured to sustain all processes mentioned above a) Anaerobic for Bio-Gasification b) Aerobic for COD/BOD removal and Nitrification c) Anoxic for de-nitrification.
PROCESS DESIGN
Process design to achieve NGT standards as per Table 3 and civil sizing of various operational units to achieve the treatment is shown in Table 4. The Area mentioned is the inside area of each unit, Fill Volume is the volume of water or bio media to be filled in each unit. Based on Free Board the actual built volumes will change. The Area for ancillaries such as admin buildings, approach roads, fences, and transformer yard is extra. Bio Mounds are not water retaining structures and are to be designed as media retaining structures with PCC rafts. BMs can be executed without retaining walls using angle of repose of media itself or using Gabions filled with media.
MERITS & DEMERITS
Merits
High outlet Quality discharge suitable for recycling for Horticulture and Other non human contact use.
High efficiency removal of COD/BOD/Nitrogen/Phosphorus/Fecal Coliforms
Low Footprint (400-600 sqm/MLD) as compared to ASP.
Low O&M costs due to low power consumption.
Ease of Maintenance due to Minimal Electro-Mechanical Equipments
80% of plant area can be Green increasing the aesthetics of plant area
High outlet Quality discharge which can be recycled for Horticulture and Other non human contact use.
The system can be constructed to any size on modular basis and scaled up for bigger capacities for larger cities.
Retrofitting of existing ASP plants to CAMUS standard is possible
By using special high adsorption media Plant can be designed to higher outlet quality (BOD<5) to supply to industries by an additional expense 30% thus avoiding membrane technologies which require high capital and operating cost.
There is no danger of flooding due to Plant units all being built substantially above ground (GL+4m)
Demerits
Constraints in Availability of Granular Media Locally requiring installation manufactured media
Improper operations by untrained or unlicensed operators of CAMUS may lead to significant damage to the Bio Media and reduction of process efficiency which may require significant CAPEX to restore function
CONCLUSION & RECOMMENDATIONS
CAMUS stands as a proven, cost-effective, nature-centric technology, locally developed to treat municipal and low TDS (<2500 ppm) industrial wastewater. It boasts numerous functional installations in various setups (STP/FSTP/ETP). An illustrative case involves a 6.3 MLD capacity STP in Mulbagal, Karnataka, commissioned by the Karnataka Urban Water Supply and Drainage Board. Distinguishing itself from aerated technologies, CAMUS doesn't rely on emergency power to sustain its biofilm when power is absent, unlike other systems needing Diesel Generators (DG) for maintaining MLSS in aeration basins. If DG backup is provided for continuous operations (24-7), CAMUS requires only a fraction of the power compared to typical aerated technologies.
Its robustness extends to functioning under intermittent power and wastewater supply, contributing to significantly lower life cycle costs and minimal maintenance needs compared to alternatives. Moreover, CAMUS technology allows for retrofitting existing STPs. It's recommended that the executing Contractor utilizes certified porous granular bio media, patented cultures, and catalysts specific to CAMUS, provided by the Technology Provider. Additionally, for optimal long-term functionality and meeting treatment norms, Operation and Maintenance of these facilities should be carried out by trained and licensed operators, closely supervised by the Technology Provider. These crucial aspects could be appropriately integrated into the tender documents.
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