A
paper in conjunction with Industrial Waste
Management Conference 2.0 on 18 & 19 November 2014 in Empire Hotel Subang Jaya,
Malaysia, organized by Asia iKnowledge Sdn. Bhd.
Preamble: Resource Depletion will continue to be a challenge and therefore that should prompt keener exploration in waste recycling opportunities. With adequate facilitation, recycling of hazardous waste are on-going endeavors which should impede current rate of resource depletion. An assignation between waste generators and legal enforcers is the best deal to cobble its success. Sludge, for this discussion, is normally the final waste of an industrial effluent treatment system. It usually contains toxic if not obnoxious constitutes and thus classified as Scheduled Wastes. These inherited jargons have intoxicated our minds with too much fear. The realm of environmental technology recognizes them as resources! They were from the environmental resource but transformed. We need to retransform them into useable products using technological innovations. Innovative ideas must be nurtured with adequate feeds from top management and facilitated by empathetic legal supervision. Then, we can turn stones to bread, literally.
The industrial effluent is generic in its type. It is based on their major or ‘parent’ composition. In other words, where it originate. Typically, the inorganic type of effluent contains mostly of trace metals and salts which contributes to high chemical oxygen demands (COD). On the other end, organic effluent consists of mostly biodegradable organic compounds which pose high demands for oxygen for its biological oxidative decomposition. In between them is a class that challenges us, thus, requiring further or specialized treatment.
This
is a generalized flow of treatment phases involved from a holistic viewpoint.
Primary
treatment; is aimed to remove foreign matters in coarse or bigger sizes
e.g. grass-cut debris, fibres of fruit and pulps, scum of fatty matters,
resins, adhesives, etc. that may upset the IETS, such as clogging pumps, valves
and pipes.
Secondary treatment;
e.g. in biological systems –anaerobic or aerobic decomposition of organic
matters to ideally H2O and CO2 plus dead cells in sludge
forms that settles in clarifiers. In chemical treatment – inorganic
pollutants removed by coagulation & flocculation – settles – sludge.
Treated effluent is ‘wholly’ water, meaning; its chemical or foreign inhabitants are almost fully removed. At this point it may not be as healthy as rain, ground or spring water. However it poses less pollution loading into its respective receiving water bodies and the latter have more time and natural capacity to assimilate residual traces of pollutants upon its entry. If treated effluent is chosen to be recycled then it is wise to lay down the exact recipient or purpose to ensure that it fits. In other words objective recycling eases the selection of tertiary treatment options.
Ponder on this! Pay to take water then pay to treat them and eventually paid for their disposal. Water is a renewable resource. Industrial businesses that uses it pays from treated water suppliers as material costs in xRM/m3. In remote cases, some others resorted to ground water. These process waters are contaminated as it leaves the production system and needs to be treated to levels acceptable to the law prior discharging it back into water ways. Treatment consists of both fixed capital and running costs. By the time this water is released its value has actually appreciated more than xRM/m3 Is this captured or merely adjusted as capital loss? No wonder that most financial controllers aren’t impressed with such expenditures.
Zero discharge for an IETS is when it simply does not release any water into public drains or any external water bodies. Nonetheless, it appears desirable in diagrams than in practice. Despite being treated to qualities surpassing Standard A of the Malaysian law, several factories had to learn about RO membranes in an expensive manner. Their elation from its initial success was short-lived when these membranes frequently clogged and had to be replaced repeatedly. One company was allured to installation of fittings to its canteen area as an alternative source of drinking water. It was a greatIdea which worked. However, it was noted that backwashing became more frequent than what was written in its operational manual. A number of internal samplings and analysis discovered the presence of several metallic and mineral salts in ppb which have occupied the membrane pores and clogged them. Although no significant scaling was detected but stains were evident. “On a RO membrane, the calcium molecules block the membrane, making backwashing necessary on a regular basis."(1) Clogging of membranes in filtration systems seemed inevitable. According to Michael Corey Adams (2), “while fouling cannot be eliminated completely, processors may limit its progression by choosing membrane materials which adsorb less foulant, optimizing processing conditions such as cross-flow velocity, temperature, and TMP, pre-treating system feeds to reduce their propensities to foul, or adopting novel technologies which seek to limit fouling.” Hence, in expense of its R.O.I’s unbalanced sheet a Plan-B for this company came to light. A simple tank buried next to its IETS final overflow, a submersible pump connected to existing RO water pipes, by-passing the RO and a slight deviation into toilets’ main tanks and disconnected them from external water supply. Eventually this company doesn’t pay to flush toilets which cater for its 500 odd workers. A renewed water resource tapped quite cheaply. But, this isn’t absolute Zero Discharge as they bragged. Their toilet wastewater or sewage enters a common sewerage pipe into centralized sewerage treatment plant owned by a government licensed operator. Noteworthy though is the fact that they are able to reuse treated effluent released from their IETS.
Effluent releases from the agro-based industry are mainly organic and contains high calorific values and nutrient constituents. A Malaysian palm oil mill has won the Asean Energy Award for generating biogas in volume rates enough for consumption by its quarters. Apart from methane by-products they can be further used as fuel to power steam turbines and thus producing electrical energy. According to a publication, the estimated potential energy generated from biogas in Malaysia is 1.88 million MWhr of electricity which is equivalent to 261 MW of the potential power based on 21% efficiency in a steam plant (based on yield of FFB in 2009)(3) Despite the greener energy from what is known to be renewable resource (as palm oil crops are renewable) current efforts are still not connoting to endeavors which glorify renewable energy from waste. Hence, many mills are still releasing methane into the atmosphere in addition to their release of other greenhouse gases from open anaerobic ponds and mulching activities much enough to amaze the Kyoto Protocol. According to a publication by SARAWAKENERGY, an additional source of energy in palm oil mills is the biogas produced in the anaerobic decomposition (for wastewater treatment purposes) of POME. Presently, POME-derived biogas is not recovered and used. This CH4 rich (65 %) gas is allowed to dissipate freely into the atmosphere.(4)
Everything on earth comes from the earth and shall be returned to earth. But, the problem prevails when we return them in forms unaccepted by the natural environment. Thus, nature reacts and displays its imbalanced conditions known by many as the environmental impact. Even ashes from secured landfills eventually liquefy to form leachate. Is a secured landfill absolutely secured? Are the PVC linings and clay walls that partially encapsulate its structure not affected by meteorological factors especially from the constant earth vibration? Those tectonic plates are noted to be unstable. Furthermore, how much more prime-land-to-be should be sacrificed for this deep ‘impoundments’? When sensible choices are as scarce as land area for waste disposal and incineration is an unpopular option under Kyoto Protocol then innovative ideas must be prioritized. Sludge, in most cases are containing toxic constituents of trace metals or better known as heavy metals. They are common products of the coagulation and flocculation processes of an IETS. So, they are perceived unwanted and in many ways over proportionally dreaded. But, we can ‘tame’ them with sound engineering practice. We learned that toxic substances are destructed at temperature over 900oC, except Dioxin and Furan. The author assisted a couple of ‘interested parties’ in providing theoretical formulations and options in heat-curing industrial sludge into some useable products. It only took them three months and about twelve trials before they arrive to the optimum composition to turn their sludge cakes into paver bricks. Surprisingly the TCLP test on those bricks seems safer than some conventional bricks meant for buildings. This finding goes unpublished until this day to avoid legal misconception and apprehension locally. However, a published report elsewhere supported this fact. “Toxic characteristic leaching procedure (TCLP) tests of brick also showed that the metal leaching level is low. The conditions for manufacturing good quality bricks is 10% sludge with 24% of moisture content prepared in the molded mixtures and fired at 880–960 °C.”(5) These ‘sludge-bricks’ may have unconventional colors as compared to the stereotyped earthy reddish colors of a commercially produced brick in this country, but, in terms of its applicability in the construction sector and environmental neutrality, they are compatible if not surpassing the Malaysian Standards. “The physical, mechanical, and chemical properties of the bricks that were supplemented with various proportions of dried sludge from 10 to 40 wt% and generally complied with the General Specification for Brick as per the Malaysian Standard MS 7.6:1972, which dictates the requirements for clay bricks used in walling in general. A standard leaching test method also showed that the leaching of metals from the bricks is very low.”(6)
The author compares heat curing of clay, clay-like mixtures and several industrial
sludge and found similarities and differences amongst them. One major factor
which influences their success in transforming into a commercially viable brick
product is the atterberg limit. This
factor, curing time and temperature seems to relate to the strength of this ‘sludge brick’. Too much dewatering has
led to brittleness despite having good strength. Further trials in adding auxiliary materials such as cement
paste, cement and gypsum at variable proportion were done.The local makers of traditional pottery such as
the ‘Labu Sayong’ uses lower
temperature but prolonged curing time inspires this work as much as the higher
temperatures of a Taiwanese Kiln.
They are similar due to the presence of clay matter and moisture content. The
‘sludge brick’ has additional challenges; to be technically cured, and destruction
of its toxic content. Detoxification by intra-encapsulation with the use of
auxiliary materials and demobilization by chemical fixation promoted by the
heat treatment are producing more desired results. They are strong and safe
‘sludge brick’. The ‘owner’ who provides the sludge for studies are already
using them in their gardens and walkways a couple of years before this
‘disclosure’ is being written. Nonetheless, the author is still viewing such
achievement as a pre-prototype. A few ‘final touches’ to ensure higher level of
inertness and stability has not been experimented. They (the owners and
contractors) are already contented with the low TCLP results thus complacence
from investing more time and effort. The elation for the pre-prototype sludge brick is just an intrinsic substance for the
author. The fact that the product worked and to this date has not shown any
sign of cracks or erosion is an amazing feeling for it was developed from a
‘back-yard science lab’. A report which is believed to use a different sludge
origin and test parameters seems to support this finding. They stated that “Density of bricks,
compressive strength and ringing sound reduces as sludge content in bricks
increases whereas water absorption and efflorescence increases. Higher firing
temperature and firing period i.e. 8000 C and 24 hours give good results in
terms of compressive strength with same percentage of sludge as compared to
other temperature and firing period combinations. Textile mill sludge up to 15%
can be added so as to get compressive strength greater than 3.5 N/mm2“(7). The compressive strength property of the pre-prototype sludge brick wasn’t tested in accredited laboratory
but evident from use. Well, Mr. Newton wasn’t in the lab when an apple fell on
his head and theorized his first law, was he?
Innovation
Undergraduates need more
practical-minded supervisors who
encourage them to try new ideas which benefit the community in terms of environmental products and
due-diligence. Supervising lecturers and tutors should be given the liberty and
opportunity to work closely with the
industrial sectors and seek opportunities for short term researches in favor of
their students.
Experienced factory
personnel do have ideas for environmental improvement.
Hierarchical barriers often impede the communication of inexpensive but ingenious proposal from the bottom.Good bosses are
not just always right but are those who are willing to comprehend the sustainability of businesses they are
working for, thus, in this regard; he who wields innovations to yields.
Finance
Besides grants for researches,
universities’ research groups should also be directly funded by industries that have viable and potential research
targets delegated to these intellects. Insensible protocols needs to be checked
when the integrity of such research teams is already in place and progress well
monitored.
Legislation
The law shall always be respected. Those who subscribe
to them know how heavy the judicial liabilities are. Does this scare them too
much? The intention of this law is for ‘enhancement
of the environment’. In practice, its execution in certain areas are
indifferent to an objective of the environmental management that is recycling. A clear example is the case
of this ‘sludge brick’. For the law, it is a Scheduled Waste for its heavy metal content prior the conversion
and shall remain so regardless of its transformed nature and application. If ‘cradle to cradle’ is the slogan for
scheduled waste management now, this ‘sludge brick’ and a few others is ready
for their debut to complement such noble statement. A deeper empathetic sense
on all recycling effort is needed. Above all, the manner by which the law book
is written demands enforcers to exercise it with greater fiduciary for the
natural resource management – thus, thwarting the impetus of resource depletion.
References
2.
Michael
Corey Adams, January 2012, EXAMINATION OF METHODS TO REDUCE MEMBRANE FOULING
DURING DAIRY MICROFILTRATION AND ULTRAFILTRATION, Cornell University, pg.33
3.
NATIONAL
BIOGAS IMPLEMENTATION (EPP5) BIOGAS CAPTURE AND CDM PROJECT IMPLEMENTATION FOR
PALM OIL MILLS; MPOB, 1 January 2013. P-6
4.
http://www.sarawakenergy.com.my/index.php/r-d/biomass-energy/palm-oil-mill-effluent
6.
Abdul G. Liew, Azni Idris, Abdul A. Samad, Calvin H.K. ong, Mohd S. Jaafar, Aminuddin M. Baki, ‘Reusability
of sewage sludge in clay bricks’, Journal of Material Cycles and Waste Management, March 2004, Volume 6, Issue 1, pp 41-47
file:///G:/Downloads/IJEP10270-20130531-165647-4825-10621.pdf)
Khalid Mohd Ariff
Trainer/Director
Sekitar Synergy Sdn Bhd
October 28, 2014 - Muharram 4, 1436H
No comments:
Post a Comment