Journal of Chemistry and Chemical Sciences, Vol.

6(11), 989-996, November 2016 ISSN 2229-760X (Print)

(An International Research Journal), www.chemistry-journal.org ISSN 2319-7625 (Online)

Is Zero Liquid Discharge a Feasible Solution?

Payal B. Joshi

Mukesh Patel School of Technology Management & Engineering,

SVKM’s NMIMS (Deemed-to-be-University),
Bhaktivedanta Swami Marg, Opp. Cooper Hospital,
Vile Parle, Mumbai-400056, Maharashtra, INDIA.
email: payal.joshi@nmims.edu.

(Received on: November 7, 2016)

ABSTRACT

Strict environmental regulatory norms, water scarcity and growing

awareness of environmental issues are the major drivers for adoption of zero liquid
discharge (ZLD) technology in industries. This article presents a review on concept
of zero liquid discharge, processes involved, examples of ZLD treatment plants in
textile, pharmaceutical, and metal finishing industries, challenges, opportunities and
feasibility in application-specific industrial setting.
Keywords: zero liquid discharge, waste water.

INTRODUCTION

NEED FOR ZERO LIQUID DISCHARGE

Water is required in several industrial processes such as steam generation,
crystallization, scrubbing, extraction, etc. After the use of water in multiple processes it leads
to formation of waste water streams that is disposed after suitable treatment. This is called as
the ‘end-of-the-pipe’ non distributed waste water clean-up 1. It is already a known fact that
water is a limited resource, therefore adopting methods to reuse water is a plausible solution.
However, water reuse in industries will require complete cleaning treatment techniques. Water
reuse, stricter environmental regulations on industrial effluent release and Clean Water Act
(1974, revised 1977, 1982) are the major factors for ‘zero discharge’ or ‘zero-liquid
discharge’2. It is suggested that these regulations should be strengthened as new EPA
guidelines are expected in 2017 and 2022 with special emphasis on zero-discharge3.
Zero liquid discharge (ZLD) is a process where all industrial waste water can be reused
after recycling without discharging a drop into natural water bodies. This concept is also
extended to municipal waste water. ZLD is not a new concept, thought its conceptualization
and application in industry took a slow paced growth4.

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In 1997, Formosa Plastics Corporation signed an agreement with Wilson, the

Environmental Protection Agency (EPA), Texas Natural Resource Conservation Commission
(now Texas Commission on Environmental Quality) and attorney Jim Blackburn to reduce its
discharge of wastewater to zero. As a result of Wilson-Formosa Agreement, a comprehensive
analysis towards reaching zero discharge system was commenced. According to the
agreement, the list of candidate solutions were developed that is economically beneficial,
environmentally superior and technically proven to be effective in a similar industrial
application5.
According to second law of thermodynamics, there is no ‘zero discharge’ possible, as
it clearly states that conversion of thermal energy to useful work necessitates a certain amount
of energy must be released6. Thus, complete recycling is a complex chemical factor that seems
virtually impossible. Industries and small-sector enterprises have adopted zero-to-near zero
discharge techniques. The industries where ZLD can be adopted are power plants, fuels, metal
processing, pulp-paper, petrochemicals, oil refining, fertilizer, textiles, pharmaceuticals,
tannery and ethanol production.

TECHNIQUES TO ACHIEVE ZERO DISCHARGE

In general, industrial effluents contain high concentrations of salts, suspended total

dissolved solids (TDS), chemical oxygen demand (COD), toxic compounds like heavy metals,
dyes, surfactants, chlorinated solvents, etc. The goal of zero discharge is to recycle all treated
waste water back into the manufacturing process. In India, as per CPCB notification (2015),
guidelines for zero discharge for water-polluting industries were drafted7.
Most industries use water in different processes based on the applications. Hence, the
waste streams generated is widely varying in composition. One of the main problems when
designing a ZLD system is determining the type of waste stream generated. Composition of
effluent water, flow rate and purity demand of water are some factors that are essential while
designing a ZLD system. As the concentration of effluent is varying, it is challenging to design
a generic ZLD system. In simplest terms, a typical ZLD system comprises of:
a. Pre-treatment (Physico-Chemical and Biological)
b. Reverse Osmosis (Membrane Processes)
c. Evaporator and Crystallizer (Thermal Processes)
Pre-treatment operations include use of screens/filters for removal of larger materials,
followed by grinding of solids, pre-aeration for odour control, pH correction and removal of
oil & grease. Various physico-chemical methods like flocculation, sedimentation, and
neutralization are performed which effects the reduction of TSS and BOD levels and prepares
the waste for the next step in the wastewater treatment process. This process involves
decomposition of suspended and dissolved organic matter in waste water using microbes.
Commonly used biological treatment processes are activated sludge or biological filtration
methods. Biological treatment processes mainly used for secondary treatment are based on
microbial action to decompose suspended and dissolved organic compounds present in
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wastewater. Trickling filters and activated sludge methods are commonly adopted biological
treatments methods in most industrial plants. Membrane technology is considered as the
tertiary waste water treatment process used for removal of trace suspended solids from
effluents of chemical treatment processes. This is also a membrane separation method that is
used to remove several types of large molecules and ions from solutions through application
of pressure to the wastewater on one side of a selective membrane. The result is that the
contaminant is retained on the pressurized side of the membrane and the treated waste water
is allowed to pass to the other side. Use of activated carbon, UV rays, ion-exchange methods
are also employed for the purpose. The above processes are advanced waste water treatment
technologies utilized in tandem to achieve ‘near-zero’ to ‘zero discharge.’8
Designing and installing different discharge technologies is labor intensive and
expensive. Hence, European Union Member States are required to implement the IPPC
Directive in national law and ensure the existence of rigorous approval requirements on the
basis of best available techniques (BAT). The Integrated Pollution Prevention and Control
(IPPC) Directive 2008/01/EC of the European Union form the basis within the European
Union of the permit procedure for industrial installations. The IPPC Directive is based on the
concept of Best Available Techniques (BAT)9. Some case studies have been presented
including textile, pharmaceuticals and metal finishing.

Textile Industry:

It is considered as the major water intensive sector producing effluents with high levels
of TSS, dissolved fibres, enzymes, starch, BOD, bleaching agents, surfactants, salts, resins,
waxes, urea, alkalies, hydrocarbons and dyes10. European companies increasingly import
textile products from outside the EU, especially from developing countries like India and
China. These products are finished in the EU, or sold directly. Hence, there is an urgent need
to streamline zero-discharge technologies to be comparable with industries in the EU.
The illustrative example is of Tirupur textile plant in Tamil Nadu, India, where ZLD
technology is adopted. In view of the deteriorating water quality in Noyyal river making it
unfit for irrigation, Madras High court made it mandatory for the polluting industries to have
zero liquid discharge (ZLD) system. Ninety units were closed for not providing zero liquid
discharge system. Based on the directions of the Madras High Court and TNPCB in 2005 the
bleaching and dyeing units in Tirupur implemented CETPs and IETPs to meet the Zero Liquid
Discharge (ZLD) norms.
Based on Fig.1, technology involves common effluent treatment plant (CETP) reverse
osmosis and mechanical vapor recompression for the final reject of effluent.
These tandem methods result in high recovery of water (>90-95%) along with
recovery of salt. Table 1 lists the common brine disoposal methods. The challenges seen are
reverse osmosis reject containing hardness, organics, silica and other contaminants which
affect evaporator performance. Further, the salt produced gets contaminated with the RO reject
salts resulting in issue of waste salt disposal.
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Table 1: Selected brine disposal methods.

Method Limitations Covered under
regulation
Recycle for Specific to effluent composition __
industrial use
Surface water Sufficient assimilative capacity should exist in water Clean Water Act
discharge body to accept discharge (1975)
Land application Existing drinking water aquifers to be protected, Safe Drinking Water
appropriate soil parameters Act (1974)
Evaporation ponds Land availability, higher evaporation rates, drinking Safe Drinking Water
water aquifers to be protected Act (1974)

Fig.1: ZLD overview in textile industry.

High scaling (due to hardness) and corrosion (from chlorides) results in poor
performance of the equipment. Crystallization of mixed salts in industrial effluent is complex
and energy-intensive method. High operating costs as a typical crystallization costs after MVR
is in the range of 600 to 650 (INR) per m3 of feed. However, possible improvements involve
use of multi-effect evaporator for RO water permeate followed by crystallization of salts and
their reuse. The other side of the case was recently reported where the plant is struggling to
exist with stringent guidelines11.

Pharmaceutical industry: In general, pharmaceutical waste comprises of organic

compounds, high COD, toxic solvents like methanol, isopropyl alcohol, ethanol, and minimal
suspended solids. As suspended solids are in trace amounts, the first step of treatment is
chemical precipitation followed by biological processes. Organic compounds present in waste
sludge are of varying nature ranging from emulsions, colloids to binding/chelating agents.
AstraZeneca is involved in discovery, development and manufacture of therapeutic
drugs for serious illnesses like cardiovascular, gastrointestinal, neurological, cancer,

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respiratory and inflammation. AstraZeneca effluent plant at Avlon Works, Avonmouth, UK

has been designed to meet the current and likely future expansion of effluent load from the
plant along on site effluent treatment. The advanced control system incorporated at the site
allows remote administration of the SCADA (supervisory control and data acquisition) system,
allowing retaining of historical data to back check the efficiency of waste water plant.
The plant divides effluent streams as per COD levels. Effluent is sent in a lamellar
separator followed by blending tank to eliminate carbon particulates (Fig.2). Next, the effluent
is sent in a fungal bioreactor maintained at pH=4.0 which is then raised to pH = 7.0 to allow
bacteria to proliferate. Effluent streams are treated in a moving bed bioreactor (aeration and
agitation) followed by phosphate removal and dissolved air flotation plant where final sludge
is separated and sent for safe disposal making it a ‘near-zero’ plant12. Biomass flocculation is
done by adding ferric sulphate in minimum dose. Fungal bioreactor removes 60% of the COD
load while the bacterial reactor can eliminate 80% of COD load.

Fig. 2: Typical zero discharge in a pharmaceutical industry.

Metal finishing Process: Metal finishing industry is one of the largest industrial activities that
involve wide range of chemicals, especially heavy metals. If the effluent is not properly
managed, it can adversely affect public health and environment. One of the metal finishing
processes is electroplating that involves deposition of a thin protective layer (metallic) on a
base metal, using electrochemical processes. This process imparts corrosion protection,
surface hardness, aesthetical attributes like colour and lustre (Fig.3.)

Fig. 3: Schematic diagram of electroplating process.

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In a typical electroplating process, base metal is made cathode and the coating metal
is made anode dipped in an electrolytic bath. The process involving cleaning and pre-treatment
stages use toxic solvents like chlorinated hydrocarbons and surface tripping like caustic soda
and strong acids like hydrochloric and sulphuric acids, depending on the metal surface to be
plated. Fig 3, depicts general electroplating process line and composition of effluent streams
from various steps. Generally, waste water from metal finishing units comprise of heavy
metals such as cyanide, hexavalent chromium, total chrome content, acid waste, metal salts,
oils-grease emulsions, and other dissolved solids13.
As depicted in Fig 4, oily waste water stream is mixed with alum, followed by
demulsification and oil is skimmed by gravity settling. Cyanide oxidation involves destroying
cyanide via reacting with sodium hypochlorite in NaOH conditions. Hexavalent chromium
reduction to trivalent form (Cr6+ Cr3+) is done in batch process using sodium bisulfite in
acidic conditions or continuous process using sulphur dioxide in HCl conditions.

Fig. 4: Typical metal finishing wastewater treatment flow diagram.

After reduction, trivalent chromium is precipitated as a hydroxide and separated.

Chemical precipitation of dissolved and complexed metals is achieved by reaction with
hydrated lime and removal of precipitates by gravity settling in a clarifier. pH for metal
precipitation is maintained in the range of 8.5-11 depending on the mixture of metals present.
Sludge obtained from various stream treatment is later dried using gravity drainage and
evaporation processes. Precious metals are recovered from solvents and reused as catalysts,
electrode making, etc. Rinse water is also recycled and reused.
As per COINDS (2007), there are above 600 automatic electroplating plants in the
country14. Electroplating operations can be found as individual plating units or form part of
large scale manufacturing plants or as smaller units employed for specific needs.

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Electroplating units operating in Ludhiana, India is one of the best examples of zero-to-near
zero discharge plants. With over 500 electroplating units operating in Ludhiana, there is
generation of toxic effluents containing heavy metals like nickel, zinc, chrome, copper, iron
etc. CETP for these electroplating units is working on zero liquid discharge technology and no
effluent is practically discharged. The treated effluent from electroplating units is reused by
dyeing industries. Treatment process used by CETP comprises of physico-chemical treatment
as a primary treatment, followed by biological treatment. After this, activated sand filters are
used followed by ion exchange, reverse osmosis, and finally multi effect evaporator techniques
to obtain final treated effluent, which is reused, thus making this CETP a ZLD setup with TSS
discharged in negligible concentrations.

CONCLUSIONS

Several industrial plants have achieved near zero liquid discharge (n-ZLD) such as
textile, pulp-paper, metal-finishing, distilleries, tanneries, power plants, etc. Near-zero liquid
discharge seems a plausible solution in major industries, but face challenges. Due to high
capital costs, energy intensive steps, near-zero-to-zero discharge technology is still at a
primitive stage in India. The major shortcoming of ZLD is that no single technique can be
employed for effluent treatment as each effluent stream composition is different, hence
common effluent treatment plants (CETPs) are facing serious challenges. Though,
thermodynamically, it is improbable to attain zero discharges, utilizing mathematical
programming, except some industries, zero liquid discharge can be employed15. The global
estimates reveal that total market potential of ZLD may reach 210 billion by 202016. Water
was always considered an underpriced resource, but with the implementation of zero-to-near
zero discharges, there is a shift in focus where polluters need to devise methods to achieve
least environmental impact (EI).

REFERENCES
1. Belhatche D.H. Choose appropriate waste water treatment technologies, Chemical
Engineering Progress, 91(8), p.32-51 (1995).
2. Clean Water Act, https://www.epa.gov/laws-regulations/summary-clean-water-act (2016).
3. https://www.epa.gov/smm/epa-sustainable-materials-management-program-strategic-
plan-fiscal-years-2017-2022 (2016).
4. Ford D. Zero-Discharge & Environmental regulations, the Toxic release Inventory &
Natural laws, Environmental Engineer, 32(4), p.10-23 (1996).
5. Blackburn J, Ford D, Wilson-Formosa Agreement-Summary (1998).
6. Mortimer. R.G, Physical Chemistry, Academic Press, 3rd ed, p. 106 (2000).
7. Guidelines on Techno-economic feasibility of implementation of zero liquid discharge for
water polluting industries, CPCB (2015).
8. Karia.G.L, Christian.R.A, Wastewater Treatment: Concepts and Design Approach, PHI
Learning Pvt. Ltd., Delhi, 2nd ed (2013).
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9. Promotion of Best Available Techniques (BAT) in the Textile and Leather Industry in
Developing Countries and Emerging Market Economies (2003).
10. http://eippcb.jrc.ec.europa.eu/reference/ (2016).
11. http://economictimes.indiatimes.com/industry/cons-products/garments-/-
textiles/tirupurs-textile-industry-struggling-to-stay afloat/articleshow/50606811.cms
(2016).
12. Environmental sustainability, report by AstraZenenca, Sustainability Update (2015).
13. Cleaner Production in Electroplating Industries, Information Bulletin, APPCB (2004).
14. Comprehensive Industry Document on Electroplating Industry (COINDS), CPCB (2007).
15. Anantha P.R, Bagajewicza.M.J, Dericks.B.J, Savelski. M. J. On zero water discharge
solutions in the process industry, Advances in Environmental Research, 8(2), p.151–171
(2003).
16. www.ckinetics.com (2016).

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