Reuse and Recycling of Wastewater Through Eco-Friendly Approach

Introduction The disposal of industrial wastewaters posing problem of increasing importa nce throughout the world. One of the major sources of contamination of gro und water sources or soil is the indiscriminate disposal of untreated or parti ally treated industrial wastewater. The increasing technological developmen ts though helped the mankind but at the same have led to environmental degr adation. Therefore environmentally and ecofriendly approach is required for safe disposal of industrial wastewaters on land. Land application through hi gh rate transpiration system (HRTS) for treatment of industrial wastewater h as been considered as a low cost, low – tech method for improving its quality for potential reuse. The present paper describes the safe disposal of treated c oloured pulp and paper mill wastewater on land through HRTS, one of the e cofriendly technology, was designed and developed. This consists of speciall y designed ridges, planted with suitable plant species and furrows laid with f ilter media for treatment of wastewater. After making laboratory evaluation of the system,

Concept of wastewater management leading to zero discharge using HRTS

HRTS implemented at field scale

1.Orient Paper Mills, Amlai, Madhya Pradesh 2. Mahindra Vehicles Manufacturing Limited, Pune, Maharashtra 3. TALCO, Tannery industrial cluster, Ranipet, Tamil Nadu 4. Puri sea beach for domestic wastewater

etc..

Treatment and Disposal of Pulp and Paper Mill Wastewater t hrough High Rate Transpiration System [HRTS]

Treatment of Pulp and Paper Mill Wastewater [Grade III] through HRT S at Orient Paper Mill, Amlai, Shahdol [M.P.]

Treatment and Disposal of Tannery Wastewater through High Rate Transpiration System [HRTS] Introduction of aromatic grasses like citronella and lemon in the HRTS hel ps to improve ambient environment i n the following manner:  in controlling obnoxious odours resu lting from evaporation wastewater f rom the furrows

Plantation [After 24 months]

 in controlling breeding of mosquitoe s and other insects due to astringent and repelling aroma from the grasse s  effective check on cattle trespassing as cattle do not browse on these gra sses thus preventing cattle damage to HRT system

Plantation [After 12 months]

 in controlling growth of harmful wee ds like parthenium etc.

HRTS Installed at TALCO, Ranipet [Tamil Nadu]

Current Approaches for Treatment of Industrial Wastewater

 Traditional methods for dealing with different industrial wa stewater comprises of various combinations of physical, che mical and biological methods. Some of them include 

Physical treatments includes dilution, equalization, separation, sc reening, sedimentation, etc. and this process removes suspended , precipitated or flocculated solid particles from the wastewaters.

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Chemical treatments includes neutralization of the wastewaters with acids or alkalis, coagulating agents like alum, ferrous sulpha te, ferric sulphate followed by flocculation and sedimentation.

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Biological treatment consists of mixing industrial wastes with oth er wastes such as the sanitary waste, oxidation by compressed ai r, trickling filters, activated sludge treatment, oxidation ditch, lag ooning, etc to bring the BOD of the wastewaters within the stipul ated limits.

Need for More Elaborative Wastewater Management System

 The present wastewater treatment systems are costly, re quire high energy and money inputs.  Their maintenance cost is very high and are non recurring .  Also, the conventional methods to remove the colour fro m the industrial wastewaters are not economically viable at plant scale. Therefore, to tackle the colour problem, an environmentally friendly technology, i.e. High Rate Trans piration System (HRTS) developed by NEERI for safe disp osal of tannery wastewater.

High Rate Transpiration System

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The High Rate Transpiration System [HRTS] envisages th e use of dynamic, multi-component soil system as a living filtration device to renovate the wastewater through ads orption, ion exchange, precipitation and stabilization of p ollutants through microbial degradation.

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The high transpiration capacity of plants grown on soil m atrix enables the system to serve as a biopump.

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In addition to this, artificial filter media and leaf fall from standing plants provides thick mat and forms a filter bed, which is responsible for retention and assimilation of colo ur bodies.

Contd….

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The High Rate Transpiration System (HRTS) is a land application system wherein the wastewater is applie d in specially designed field layouts with wide ridges and furrows, and planted with trees on ridges besto wed with higher transpiration capacity, which can co nsume the wastewater at the rate of 300 - 450 m3 w astewater per hectare per day.

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The plants grown on soil matrix transpire water equi valent of 7-13 times of potential evapo-transpiration from the soil matrix alone. Wastewater is allowed to flow through the furrows.

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Since most of the wastewater applied is consumed b y the plant there is no chance of groundwater conta mination.

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Hence HRTS is a zero discharge technology.

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Depending upon the geographical locations of the site, t he soil profiles samples were collected from different site s and were characterized for various physico-chemical a nd microbiological parameters respectively.

Collection of sample

Laboratory Studies  Bench scale experiments were condu cted using glass column for assessme nt of suitable bedding material [locall y available wastes such as coconut h usk, sugarcane husk] were selected f or large scale field application throug h HRTS.  The bedding material were selected in order to ascertain the retenti on of suspended solids present in the effluent and also to facilitate t he maintenance of appropriate moisture content in the system.  This helps in establishment of microbial community of diverse natur e in the lysimeter for better stabilization of organic matter present i n the treated effluent.  Monitoring of leachates.

Pilot Scale Experiments  Assess the optimal hydraulic load to the lysimeters to generate data for large scale application.

 Selection of pollution load of wast ewater to the lysimeter at optimal hydraulic load.  Performance evaluation of lysimet er at optimal conditions.

Lysimeters Installed at NEERI Premises

 Operate and assess the performance of lysimeter in different seasons in order to ascertain the quality and quantity of leachate produced wh ich may be a potential source for ground water pollution.  Effect of wastewater on physico-chemical and microbiological status of the irrigated soil and the growth response of the plant at optimal c onditions of the operation of the lysimeter.

Wastewater Loading  To decide the wastewater loading [m3/day], lysimeter studie s were conducted using soil profile samples + F.B.M. to simul ate the field conditions.  Lysimeters were loaded with different loadings of wastewate r loadings and varied from 50 to 350 m3/ha/day using differe nt treatments and the leachates produced were analysed and compare with drinking water quality standards.  The treatment showing no pollutant in leachate will be select ed for field application.  Based on lysimeter investigations on pilot scale, a well design ed land system with HRTS having a bedding material could tr eat the coloured wastewater at a hydraulic loading of 200-35 0 m3/ha/day.

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To study leaching of pollutants on soil and groundwater quality, piezometers were installed at wastewater dispos al sites.

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Piezometers serve as leachates collectors at various dept hs to evaluate the level of groundwater contamination.

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The water samples collected from the peizometer locate d in the HRTS sites during different seasons were charac terized for various physico-chemical parameters viz. pH, EC, alkalinity, Ca , Mg, Na, K, Cl, SO4, COD, nitrogen, and PO4.

Piezometer

Ground Water Monitoring Study at the HRTS Site To study leaching of pollutants and ground water contamination, piezo meters were installed at the different HRTS sites irrigated with waste water and also water samples of open dug well close to HRTS site wer e analysed for various physico-chemical parameters.

Parameters pH

Colour EC (dSm-1) TDS

Calcium

Piezometer

Magnesium Sodium

Potassium Chlorides Sulphates * All values except pH and EC are expressed in mg/L.

Open Dug Well

Advantages of HRTS

 Works on natural treatment processes and could t hus be termed eco-friendly.  Facilitates development of forests and green belts .  Generates sink potential for air pollutants and gre en house gases.  Low-energy and cost requirements compared to c onventional effluent treatment systems.  Ease of installation and simplicity of operations.  Biomass generation and revenue returns

Environmental Benefits of HRTS

 The results showed that HRTS provides cost effe ctive and environmentally acceptable solution  to manage the problem of coloured wastewater,  minimize the impacts on ground water quality an d  it is zero discharge option  Besides this, the system also promoted developm ent of forest and green belt and created much re quired sink potential for absorption of green hou se gases.

 The total cost of HRTS includes: Land cost  Earthwork for developing ridges and furrows.  Cost of filter media and its layer.  Cost of power arrangement at the site.  Cost towards necessary infrastructure such as motors, pumps etc.  Cost of irrigation system development through laying of distri bution piping network with control valves and the cost of requ ired civil construction.

 The operations and maintenance cost of HRTS will be Rs. 500 per month.  The cost of land application thus comes out to be Rs. 0.90 / m3 of effluent.

Cost benefit analysis of High Rate Transpiration System (HRTS): Parameters HRTS Conventional treatment (RO) Capital cost (excl INR. Ten lakhs per ha (saplings, filter media including g INR. Two Crore uding land cost) ypsum, coconut husk/ saw dust/bagasse etc ) Capacity /Area Treatment facilit y Hydraulic retenti on time Hydraulic loadin g rate Operation and M aintenance cost

2 ha 500 m3/day

400 KL 400 KLD

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1 day

80-350 m3/day/ha

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The operation and maintenance cost is high com pared to HRTS. Smaller communities cannot adopt this system because of the capital cost. Rs. 11-15/m3

Maintenance cost is minimal and operational cost  includes the electricity for applying wastewater to the system. 

Cost for water tr Rs. 4-6/m3 eatment Advantages  Ground water recharge   Carbon sequestration and oxygen production  Forestry and agroforestry development using trea ted wastewater.  A low cost zero discharge technology. Disadvantages -

A zero discharge technology

Reverse osmosis generates solid and liquid wast e which is difficult to dispose. The RO reject is hi ghly concentrated and poses environmental issu es.

Macrophytes

Raw waste water

Treated ef fluent

Influe nt

Equalisat ion tank

Soil/gravels/sand/organic mat erial

Gravel

Cement liner

Aquacultur e

Reus e opti ons Agricultur e

Collecti on tank

Floricultur e

Schematic of Phytosystem for recycle and reuse of wastewater