Sewage Wastewater Treatment with DTS Technology

The Patent Pending DTS technology offers a state of the arte solution for adequate on-site wastewater treatment taking maximum advantages of natural processes to achieve a preferably reliable and eco-friendly system. DTS technology works mostly independent from power supply and daily surveillance, treating the wastewater steady and trusty.

Since DTS is an on-site solution (decentralized or semi-centralized) the treated water can be reused locally for different purpose like irrigation, flushing of toilets, cooling and heating, washing, and groundwater recharge. Minimizing the total water consumption and its appending costs for supply, piping and pumping up into overhead tanks and allowing keeping green areas on the premises.

DTS technology can be used for domestic, hospital as well as for different kind of industrial wastewater of any volume, complying with the national discharge standards. DTS is a tailored solution taking the specific site conditions and the requirements of the client into consideration to offer the best economical and ecological option for wastewater treatment.

DTS applications are designed to meet requirements stipulated in environmental laws and regulations.

What is DTS?

A DTSis a combination of different wastewater treatment technologies cascaded in modules to a full-blown system, to achieve the required effluent quality for the claimed reuse purpose(s). The first part of the cascade always consists of three specific anaerobic modules, performing extensive wastewater stabilization in terms of organic pollution. Different options of additional modules can be added for further polishing of the water in accordance with the targeted effluent quality.

Modules of DTS

The anaerobic core modules are:

  • - (Biogas) Settler (BGST)
  • - Fluidized Bed Reactor (FBR)
  • - Fixed Film Reactor (FFR)

Plus (+) optional modules are:

  • - Plated Gravel Filter (PGF) vertical or horizontal flow
  • - Sand filter (SF) (slow, rapid, aerated)
  • - chlorine dosing station (CL)
  • - UV-treatment (UV)
  • - Maturation pond(s)

Further +-modules are possible, as per requirement!

Ecological and economical advantages of DTS technology

The core modules of a DTS use anaerobic processes for stabilization of the wastewater, which require no process energy. Since the DTS is placed nearby where the wastewater is produced, the flow into and trough the system is driven generally by gravity.

Process energy:

The DTS minimizes the requirement of process energy for the wastewater treatment; instead it produces energy in form of biogas in its anaerobic modules. This biogas can be tapped and used direct for cooking or lighting or converted into electricity via gas-generator. Hence the energy balance of a DTS is positive and power cuts have no influence of the treatment performance of the system. Due to the fact that no process energy is required but a renewable energy is produced, a DTS prevents CO2 emission and saves non-renewable resources by substitution.

Construction:

The core part of a DTS, first three anaerobic modules, are underground tanks, containing no electrical components like pumps, aerators, agitators etc. They are civil work, using local available material like concrete, cement blocks or bricks, and some PVC pipes. This optimizes the durability of a DTS and guarantees a carefree operation for decades.

The fact that the construction materials are in general locally available, long transportation can be prevented which reduced the energy (grey energy) requirement for the construction.

Maintenance:

Since the anaerobic core modules require no aeration and pumping and the sludge production is significant lower than in aerobic processes, the DTS needs for this modules minimal maintenance. Desludging of the anaerobic tanks is required only once in two years. The mineralized sludge can be co-composted with organic material or dewatered for further reuse as fertilizer and soil conditioner in agriculture or garden

Reuse potential of DTS:

Wastewater is a resource, containing water, nutrients and some energy. The DTS technology allows an extensive separation and subsequent reuse of these three components and is therefore a technical option for ecological/sustainable sanitation. The water can be reused after treatment for irrigation, flushing, washing, cooling/heating, after respective polishing modules are introduced. Part of the nutrients leave the anaerobic core modules dissolved in the water, a part settles in the mineralized sludge at the bottom of the anaerobic tanks. In case the effluent water is reused for irrigation purpose, it has also some fertilizing effect to the plants. The mineralized sludge gets periodically removed from the tanks, and becomes after some further treatment (e.g. co-composting with organic material) a valuable soil conditioner and fertilizer, which can be used for gardening and agriculture. The energy is tapped as biogas (methane), formed in the anaerobic modules of the system, and can be used for cooking, lighting or electricity production.

The treatment undergoes the following processes

Source: ADBA (Anaerobic Digestion and Biogas and Association) UK

Detailed description of the core modules

Stage 1: Settler

The settler can be considered as a gas tight septic tank with low hydraulic retention times. Two main treatment processes take place: First, a mechanical treatment retains contaminants by sedimentation/flotation, and the wastewater from the clarified layer flows through the outlet. Second, a biological treatment by anaerobic microorganisms, which partially decomposes the organic pollutant load. The digestion process ensures that the accumulated sludge is reduced and stabilized. Storage volume for sludge is provided for 18 to 24 months, defining the desludging period.

Average reduction of organic content (BOD, COD) is between 25 and 40%. The produced methane can get captured in form of biogas and be used as an energy source in direct application or electricity production via gas-generator. The settler is resistant to shock load and variable inflow.

Stage 2: Anaerobic Fluidized Bed Reactor (FBR)

The FBR consists of a series of chambers, in which the wastewater flows up-stream. Activated sludge is located at the bottom of each chamber. The inflowing effluent is intensively mixed up with the sludge, wherein it is inoculated with bacterial mass, which decompose the contained pollutants. The BOD reduction rate of the baffled reactor can be up to 90 %. The Baffled Reactor is resistant to shock load and variable inflow, the operation and maintenance is simple and virtually no space.

Stage 3: Anaerobic Up Flow – Fixed Film Reactor (FFR)

The anaerobic filter is also known as fixed bed or fixed film reactor and has a similar flow pattern like the Anaerobic Baffle Reactor. Some filter materials such as gravel, rocks or specially formed plastic pieces provide additional surface area for bacteria to settle. Non-settleable and dissolved solids are treated by bringing them in close contact with a surplus of active bacterial mass fixed on filter material. The BOD removal rate is in the range of 70-90%. The surplus of activated sludge produced has to be removed in intervals of 1 to 3 years. The AF has his strongness in further stabilization (BOD, COD, TSS reduction) of low strength wastewater e.g. the effluent from the ABR.

Treatment efficiency

The anaerobic core modules of a DTS reach high removal efficiencies in terms of organic content (BOD, COD) and TSS. BOD effluent concentrations fulfill national wastewater effluent standards concerning organic pollutants. The anaerobic treatment (absence of oxygen) disables extensive nitrogen removal. Therefore, the effluent of the anaerobic core modules contains high levels of nutrients (N and P) and is therefore just right for irrigation purpose. By introduction of additional “polishing modules” the required water quality of the projected reuse purpose can be achieved.

Space requirements

If integrated well into the existing structure, the space required for the DTS is not lost space. On the underground construction (Settler, ABR and AF) e.g. a parking space or playground can get established; PGF/Sandfliter can get integrated as a part of the Landscaping concept, aesthetically appealing and ecologically invaluable.

Thumb rule for space requirement:

To treat 100m3 wastewater, the DTS requires for:

  • The Settler, Anaerobic Baffle Reactor and Anaerobic Up flow Filter about 300m2
  • Underground tanks, the space can be used as e.g. parking space or simply covered with a plastic sheet and lawn on it.
  • Planted Gravel Filter (Wetland) about 300m2
  • Can get integrated into the Landscaping

Appendix 2 – Three Case Studies

DTS for ‘People Plus’ in Bangalore

Volume: 6m3/day
In use since: 2006
Discharge standard: BOD <20mg/l, TSS <30mg/l

Challenge 1: The Building is situated in a low-lying area; therefore it is not possible to flush the wastewater via gravity into the nearest sewer line. Soak pit is not a solution since the strata is clay.

Challenge 2: No space for a conventional STP. The treatment plant had to get integrated in a narrow space between building and outer walls.

Challenge 3: Since the treatment plant is at the entrance it should be aesthetically pleasing and the STP should be camouflaged. We overlaid the plant with a plastic liner and lawn was developed on it. To reach the manholes in case of maintenance of the DTS (desludging of the tanks) the lawn can easily get rolled up.

DTS for Manipal Hospital in Bangalore

Volume: 600m3/day
In use since: June 2008
Discharge standard: BOD <20mg/l, TSS < 30mg/l

The project was a PPP (Public Private Partnership) with MoEF, Govt. of India, German Technical Cooperation (GTZ) and Manipal Hospital.

Challenge 1: No space since the free area needs to be used as parking space. Real estate very expensive. STP is constructed below car parking.

Challenge 2: Wastewater comprises of domestic sewage, laboratory washings and disinfectives. Customized design ensured that the requirement is met.

Challenge 3: As this is a hospital, it is difficult to predict peak load. In any case if there is emergency peak load, the STP should be functional without compromising BOD levels.

We designed the STP to take care of shock loads

DTS for Aishwarya Amaze Builders

100 Apartment building at Bannerghatta Road

Volume: 50m3/day
Discharge standard: BOD <20mg/l, TSS <30mg/l

Challenge 1: Very little space available between the wall and the building. Real estate very expensive. We designed a customized solution given the space constraints.

Challenge 2: Since it is a new apartment with needs to be sold, it should be aesthetically pleasing and the STP should be camouflaged. Nearly 20 houses overlook the DTS.

Challenge 3: Given the water shortage the client wants the treated water to be recycled for toilet flushing. We designed the Planted Gravel Filter solution to address the need. The PGF was planned around the narrow space circling the building.